Piggyback tectonics: Long-term growth of Kilauea

on the south flank of Mauna Loa

Peter W. Lipman a,*, Thomas W. Sisson a, Michelle L. Coombs b,Andrew Calvert a, Jun-Ichi Kimura c

a U.S. Geological Survey, Menlo Park, CA 94025, USAb U.S. Geological Survey, Alaskan Volcano Observatory, Anchorage, AK 99508, USA

c Department of Geoscience, Shimane University, Matsue 690-8504, Japan

Accepted 15 July 2005

Available online 16 November 2005

Abstract

Compositional and age data from offshore pillow lavas and volcaniclastic sediments, along with on-land geologic, seismic, and

deformation data, provide broad perspectives on the early growth of Kilauea Volcano and the long-term geometric evolution of its

rift zones. Sulfur-rich glass rinds on pillow lavas and volcaniclastic sediments derived from them document early underwater

growth of a large compositionally diverse alkalic edifice. The alkalic rocks yield 40Ar/ 39Ar ages as old as about 275 ka;

transitional-composition lavas, which mark beginning of the shield stage while most or all the edifice remained below sea

level, probably first erupted after about 150 ka, and tholeiitic lavas of present-day type are probably younger than 100 ka. Breccia

clasts from Papau Seamount and along the lower southwest corner of the Hilina bench are derived from subaerial Mauna Loa,

requiring that Mauna Loa’s flank underlies western parts of Kilauea at shallow depth. The volume of the Kilauea edifice is

therefore smaller (~10,000 km3) than previous estimates (15–40,000 km3); lava-thickness accumulation rates appear to have

remained nearly constant during edifice growth, as effusion rates increased from ~25�106 m3/yr at end of the alkalic stage to the

present-day tholeiite rate of ~100�106 m3/yr. Seismic and gravity data show that the deep plumbing system for Kilauea’s magma

supply extends nearly vertically through the oceanic crust at least to mantle depths of 30–35 km, directly below its present-day

caldera.

Proximity of Kilauea caldera to the surface boundary with Mauna Loa and the presence of Mauna Loa rocks at shallow depth

beneath the south flank are difficult to reconcile with a submarine origin for early Kilauea alkalic lavas, unless geometric relations

between the two volcanoes have changed substantially during growth of the Kilauea shield. Seismic and ground deformation data

suggest seaward spreading of the entire south flank of Hawai‘i Island, independently of the boundary between Kilauea and Mauna

Loa, along a landward-dipping detachment fault system near the basal contact of the composite volcanic edifices with underlying

oceanic crust. Current steady-state horizontal displacements increase seaward, at rates of ~1.5 cm/yr on the lower flank of Mauna

Loa and reaching 5–8 cm/yr at the Kilauea coastline. Infrequent (~100 yr?) large earthquakes generate similar geometries, but 102

larger displacements per event.

Present-day Kilauea is the more dynamic edifice, but prior to inception of Kilauea and during its early growth, Mauna Loa is

inferred to have undergone intense volcano spreading, involving the Kaoiki–Honuapo fault system (considered a geometric analog

of the Hilina system on Kilauea). Cumulative deformation of Mauna Loa’s south flank during growth of Kilauea since 200–300 ka

is estimated to have involved N10 km of seaward spreading, displacing the rift zones of Kilauea while its deep plumbing system

0377-0273/$ - see front matter. Published by Elsevier B.V.

doi:10.1016/j.jvolgeores.2005.07.032

* Corresponding author.

E-mail address: plipman@usgs.gov (P.W. Lipman).

Journal of Volcanology and Geothermal Research 151 (2006) 73–108

www.elsevier.com/locate/jvolgeores

and summit magma reservoir remained nearly fixed in space. Kilauea’s rift zones, rather than migrating southward with time solely

due to dike emplacement preferentially on the mobile seaward side, alternatively are interpreted to have been transported passively

southward, bpiggybackQ style, during shield-stage growth of Kilauea as a blister on the still-mobile south flank of Mauna Loa. Such

an evolution of Kilauea accounts for the arcuate geometry of the present-day rift zones, proximity of the summit magma supply to

the exposed flank of Mauna Loa, initial submarine growth of the ancestral edifice, and present-day location of Mauna Loa rocks at

shallow depth beneath the south flank of Kilauea.

Published by Elsevier B.V.

Keywords: Hawaii; Kilauea; Mauna Loa; flank structure; growth history

1. Introduction

Kılauea and Mauna Loa are respectively the most

active and the largest volcanoes on Earth, and the

Hawaiian Islands have long been an archetypal example

of ocean-island basaltic volcanism (e.g., Dana, 1849;

Dutton, 1884; Hitchcock, 1909; Brigham, 1909;

Stearns, 1966; Macdonald and Abbott, 1970; Clague

and Dalrymple, 1987; Moore and Clague, 1992). As

such, Hawai‘i has been the sustained focus of detailed

studies throughout the last century, and a wealth of

volcanologic, geophysical, and petrologic data has

been acquired, especially for subaerial parts of these

enormous ocean-island volcanoes. Much less studied

until recently have been the deep offshore submarine

slopes (to depths of 5500 m), especially those below the

2000-m limit of most research submersibles available in

Hawaiian waters during the past 25 years.

Between 1998 and 2002, collaborative Japan–U.S.

research, utilizing the ROV Kaiko and manned Shinkai

6500 submersible operated by the Japan Marine Re-

search and Technology Center (JAMSTEC) made about

90 dives, mostly at depths greater than 2000 m, to study

the subaqueous geology around Hawai‘i, early-stage

growth of its volcanoes, and the giant submarine land-

slides that pose infrequent but catastrophic tsunami

hazards to the Pacific Basin (Naka and Scientific

Team, 2000; Takahashi et al., 2002). Comprehensive

SeaBeam bathymetric and side-scan sonar surveys,

made between dive operations, greatly augmented cov-

erage of the submarine flanks of Hawaiian volcanoes (J.

Smith et al., 2002; Eakins et al., 2003). Sixteen of the

dives on the south flank of Hawai‘i Island, targeted at

the underwater slopes of Kılauea and Mauna Loa vol-

canoes, have provided new insights into the early

growth and petrologic evolution of Kılauea (Lipman

et al., 2000, 2002; Naka et al., 2002; Sisson et al., 2002;

Sisson, 2003; Coombs et al., 2004a, 2006-this issue;

Calvert and Lanphere, 2006-this issue; Kimura et al.,

2006-this issue). The submarine south flank is far more

morphologically complex than the adjacent subaerial

slopes, due to preservation of earlier events in growth

of the island’s volcanic edifices at depths sufficient to

have escaped large-scale coverage by shoreline-cross-

ing young lava flows. Recent Japan–U.S. studies of the

submarine flanks of several older volcanoes along the

Hawaiian Ridge (Takahashi et al., 2002; Coombs et al.,

2004b; other papers in this issue), indicate that the flank

of Hawai‘i Island provides a unique study area, due to

the presence of a small young volcano (Kılauea) low on

the flank of a larger but still active edifice (Mauna Loa).

This report focuses on interactions between these

two volcanoes, especially evidence that their geometry

has been strongly affected by sustained processes of

gravitationally driven volcano spreading (Borgia and

Treves, 1992; Clague and Denlinger, 1994; Delaney et

al., 1998; Borgia et al., 2000; Morgan et al., 2003) that

have affected the entire south flank of Hawai‘i Island,

modifying features of both volcanoes during their

growth. Many of Kılauea’s structures, rather than hav-

ing developed solely in response to events specific to

this volcano, alternatively are here interpreted in sub-

stantial part as consequences of a blister-like Kılauea

edifice carried seaward bpiggybackQ style on the mobile

south flank of Mauna Loa. First we review the broad

geologic and geophysical framework for these two vol-

canoes, then summarize important new and published

data bearing on interactions between them during their

growth, and finally develop structural interpretations.

Central to our presentation is concern that the short

historical record and high-resolution geophysical data

document only a portion of the overall behavior of these

volcanoes. Integration with the prehistoric geologic re-

cord is key to interpreting long-term volcano growth.

2. Present-day geometry and structure of Kılauea

Numerous varied geologic, petrologic and geophys-

ical studies have documented the surface geology and

internal structure of Kılauea (e.g., Eaton and Murata,

1960; Swanson et al., 1976; Decker et al., 1987; Tilling

and Dvorak, 1993). Especially notable at Kılauea have

been the frequency of eruptions, high levels of volcanic

seismicity and associated ground deformation, and the

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10874

complex interplay between events localized near its

summit caldera and those at substantial distances

down the rift zones. Varied geometric and structural

features of Kılauea relative to Mauna Loa have long

hinted at complexly interrelated growth of these two

active volcanoes, as outlined in the following summary.

For Kılauea, salient observations include: (1) the pres-

ent map-view proximity of its summit area to the flank

of Mauna Loa; (2) the arcuate geometry of its rift zones

anomalously seaward of the summit caldera, despite (3)

gravity and seismic data indicating long-stable location

of the magmatic conduit beneath the summit caldera;

and (4) large-scale recent deformation on Kılauea’s

south flank during growth of the Hilina fault system.

2.1. Asymmetry of Kılauea

The proximity of south-flank Mauna Loa lavas to

Kılauea caldera, which marks the apex of this highly

active volcano’s deep magmatic plumbing system, is

striking and puzzling (Fig. 1). Distal lavas of Mauna

Loa extend down slope to within 2 km of the northwest

rim of Kılauea’s caldera, and the highest elevation on

Kılauea (Uwekahuna Bluff, 1242 m) stands only 38 m

above the saddle with Mauna Loa. In contrast, Kılauea

lavas are continuously exposed at the surface for 50 km

to the southeast, to the base of the island edifice at

water depths of more than 5000 m.

Such asymmetry could result from concurrent

growth of Mauna Loa and Kılauea through much of

their eruptive history, with lava flows interfingered

along a steep boundary between the two volcanoes, as

inferred in some growth models for propagation of the

Hawaiian Ridge (e.g., DePaolo and Stolper, 1996;

DePaolo et al., 2001; Baker et al., 2003). Mauna Loa

appears to have grown to close to its present size by

N100 ka (Lipman, 1995), however, while new geochro-

nologic results for early growth of Kılauea indicate that

this volcano only entered a vigorous tholeiitic shield-

building stage at b150 ka (Lipman et al., 2002; Calvert

and Lanphere, 2006—this issue). Interfingering of lava

between the two edifices seems necessarily limited to

shallow depths, late during growth of Mauna Loa.

Further complicating Kılauea’s geometry is the

newly documented existence of thick sections of sub-

marine-erupted preshield-stage pillow lavas of diverse

alkalic and transitional compositions on its south flank,

emplaced in water as deep as several kilometers (Sisson

et al., 2002; Coombs et al., 2006-this issue). From the

present-day configuration of these two volcanoes, how-

ever, it is difficult to generate a cross-section through

the south flank of Hawai‘i Island in which growth of

Fig. 1. Oblique view of present-day subaerial and submarine structures on Kılauea and adjacent lower south flank of Mauna Loa. Historical

eruptions on land depicted in black. Coarse dashed line indicates margins of Kılauea volcano; fine-dashed lines are approximate boundaries between

compositional and depositional units of Kılauea. Dashed white line, shoreline. Hachured lines, at southwest base of Kılauea submarine flank

indicate inferred large slump blocks. Digital bathymetric image provided by Joel Robinson, USGS.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 75

Kılauea above the current deep magma-supply system

(beneath the summit caldera) could have been initiated

in deep water. Even if growth of Kılauea commenced at

or near the base of a large landslide scar along the

Kaodiki-Honu‘apo fault system on the south flank of

Mauna Loa, as seems structurally plausible (see below),

a near-vertical scarp a kilometer or more high would

have been required just to reach down to present-day

sea level. Because of sustained gravitational subsidence

along the Hawaiian Ridge during volcano growth

(Moore, 1987; Moore and Thomas, 1988), the required

height of such a scarp above sea level would have been

ever greater (perhaps 1700 m above sea level at 275 ka,

plus any underwater continuation) to permit even shal-

low submarine eruption of pillow lavas from the crest

of ancestral Kılauea.

2.2. Arcuate rift zones

Oceanic-island rift zones typically are related to

edifice shape: in ideal geometry three rifts radiate at

1208 angles for an equant edifice, two opposing rifts for

elongate edifices (Fiske and Jackson, 1972; Mitchell,

2001; Walter and Troll, 2003). Rift zones of a volcano

that forms on the flank of an adjacent larger edifice tend

to be parallel to this flank, as exemplified by Kılauea’s

east and southwest rift zones aligned with the south

flank of adjacent Mauna Loa.

Long-standing puzzles concerning the structure and

shape of Kılauea have been the abrupt bend in its

proximal east rift zone to connect with the summit

caldera area along the Chain of Craters and associated

en-echelon fractures, and the role of the Ko‘ae fault

system that connects between the east and southwest

rift zone with a nearly linear overall trend. A common

interpretation has been that that the east rift zone has

migrated southward with time, caused by preferential

intrusions of dikes along the mobile south flank rather

than symmetrically along the rift crest (Swanson et al.,

1976). Additionally, it has been proposed that the

present geometry is evolving toward a single

bbreakawayQ rift system, in which the summit area is

increasingly being bypassed by extension along the

Ko‘ae faults (Fiske and Swanson, 1992).

2.3. Location of Kılauea’s magmatic conduit

The magma conduit at Kılauea has long been rec-

ognized as involving a shallow storage reservoir and a

deeper magma conduit, located directly beneath the

summit caldera (Eaton and Murata, 1960; Ryan et al.,

1981; Klein et al., 1987; Ryan, 1988; Okubo et al.,

1997), which has remained fixed in position relative to

the lithospheric mantle and oceanic crust during edi-

fice growth. Seismic and geodetic measurements pro-

vide the primary evidence for a shallow magma-

storage region at depths of 3–5 km beneath the caldera

that inflates between eruptions and deflates during

magma discharge. A large positive Bouguer gravity

anomaly (~20 mgal) centered directly beneath the

present-day summit (Kinoshita et al., 1963; Kauahi-

kaua, 1993) is inferred to record magmatic intrusions

and olivine cumulates in the feeder conduit during

growth of Kılauea (Clague and Denlinger, 1994;

Kauahikaua et al., 2000), as is also characteristic of

the crests of other Hawaiian volcanoes. A steeply

plunging concentration of seismic hypocenters, forms

a near-vertical cylindrical volume at least to depths of

30–35 km (Eaton, 1962; Klein et al., 1987, fig. 43.17),

down through the inferred location of Cretaceous

oceanic crust, well below the base of the volcanic

edifice as defined by seismic refraction surveys (Hill

and Zucca, 1987).

Positive linear gravity anomalies that coincide with

the rift zones have been analogously interpreted as due

to dense dike rocks intruded laterally along the rifts.

Several intrusive events have been documented by

seismic and geodetic data, which record dike propa-

gation from the summit magma supply at rates of

500–700 m/hr (Duffield et al., 1982; Dvorak et al.,

1986; Klein et al., 1987; Okamura et al., 1988; Cer-

velli et al., 2002a). In contrast to the deep roots of the

summit conduit, seismic and geodetic evidence sug-

gests that the rift intrusions have blade-like shapes,

confined to depths of 5–10 km within the volcanic

pile (Ryan et al., 1981; Dieterich, 1988; Okamura et

al., 1988).

2.4. Subaerial structure and deformation

The subaerial south flank of Kılauea is dominated by

seaward-stepping downdropped lenticular blocks of the

Hilina fault system (Fig. 2). Minimum displacements

on individual fault scarps are as much as 300 m, as

measured by topographic height of the scarps; total

displacement is partly concealed by lavas that locally

drape the scarps and pond at their bases. Cumulative

displacement on land is on the order of 600 m (Walker,

1969; Cannon and Burgmann, 2001), and additional

offset along the submarine continuation of the south

flank is suggested by terraces and scarps adjacent to

shoreline.

Varied geodetic measurements have documented

sustained high rates of deformation on the subaerial

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10876

south flank, involving seaward spreading and subsi-

dence (e.g., Swanson et al., 1976; Owen et al.,

2000). These motions are modified, and at times

reversed by episodic localized magma-related defor-

mation, involving summit inflation or deflation

above the magma reservoir, and rift-zone spreading

accompanying dike-intrusion events. First documen-

ted from data obtained by triangulation and leveling

surveys at the beginning of the 20th century,

Kılauea’s south-flank deformation has been subse-

quently determined with increased precision and

more synoptic coverage by electronic-distance mea-

surements (EDM), and most recently by differential

global positioning surveys (GPS). The dominant dis-

placement direction on the south flank has been

subhorizontal seaward motion (Swanson et al.,

1976; Denlinger and Okubo, 1995); displacements

increase down slope, at times having reached rates

of up to 8 cm/yr at the coastline (Owen et al., 2000;

Miklius et al., in press).

3. Submarine observations and ancestral Kılauea

The submarine south flank of Kılauea (Fig. 2) is

dominated by an elongate mid-slope bench at a water

depth of about 3000 m (Chadwick et al., 1993; Smith et

al., 1999), behind which an elliptical closed basin is

partly filled by as much as 1.5 km of sediment (Hills et

al., 2002). Above the mid-slope bench, a bathymetri-

cally subdued upper slope rising toward subaerial

Kılauea (slope angle 15–208) is inferred to be underlain

by pillow lavas and breccias mantled by basaltic sand

and coarser volcaniclastic sediments generated at the

shoreline (Moore et al., 1973; Tribble, 1991; Sansone

and Smith, 2006-this issue). The volcaniclastic sedi-

mentary mantle thins eastward; beyond the east cape

where no source of coastal sediment exists; this slope

has the typical hummocky bathymetry of a construc-

tional submarine rift zone, confirmed by bottom photo-

graphs and dive observations (Lonsdale, 1989; Clague

et al., 1994; D. Smith et al., 2002). Below the bench, a

Fig. 2. Dive sites, Hilina slump area, Japan–USA cooperative research project in 1998–2002 (sites on Seamount excluded). Contour interval, 100 m.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 77

Table 1

Major-oxide and trace-element analyses of breccia clasts and pillow lavas, 2001–2002 dives, submarine south flank of Hawai‘i Island

Lab no. Field no. Sample description [Analyses by D. Siems, USGS, Denver, Colorado]

WDXRF (wt.%) EDXRF (ppm)

SiO2 TiO2 Al2O3 FeTO3 MgO MnO CaO Na2O K2O P2O5 LOI Totals V Cr Cu Ni Zn Ga Rb Sr Zr Y Nb Ba La Ce Nd

2001 dives

Transverse scarp (breccia clasts, except as noted)

C-198891 K207-1 Talus block, vesicular basalt, 2935 mbsl 47.30 3.00 14.40 13.30 8.36 0.16 10.10 2.70 0.57 0.33 0.54 100.76 251 236 103 202 117 19 9 486 177 28 17 116 17 33 7

C-198892 K207-2 Crystalline basalt, 2988 mbsl 47.50 3.21 14.60 13.20 7.15 0.16 10.30 2.82 0.56 0.36 0.85 100.71 306 202 95 160 124 18 10 491 194 32 20 116 13 34 22

C-198893 K207-3 Crystalline basalt, 2883 mbsl 47.30 2.99 14.20 13.30 8.92 0.16 9.94 2.66 0.53 0.33 0.42 100.75 267 302 101 267 127 21 6 467 178 29 18 113 14 33 22

C-198894 K207-4 Crystalline basalt, 2883 mbsl 46.80 3.09 14.80 13.20 8.35 0.15 10.30 2.87 0.42 0.34 0.25 100.57 306 271 103 242 117 21 7 482 176 28 19 115 14 34 22

C-198895 K207-16 Basaltic pillow fragment, 2657 mbsl 47.40 3.04 14.30 13.10 8.34 0.16 10.10 2.76 0.62 0.34 0.25 100.41 289 283 97 233 124 20 9 477 183 30 20 119 15 37 14

C-198896 K207-17 Basaltic pillow fragment, 22657 mbsl 47.50 3.04 14.40 13.30 8.30 0.16 10.00 2.70 0.64 0.35 0.21 100.60 306 282 98 233 128 24 9 472 179 28 19 115 15 35 17

C-198897 K207-19 Basaltic pillow fragment, 2569 mbsl 46.80 2.93 13.60 13.60 9.67 0.16 9.55 2.57 0.63 0.33 0.40 100.24 289 346 98 296 126 23 10 455 180 30 19 109 14 30 15

C-198898 K207-20 Basaltic pillow fragment, 2482 mbsl 47.60 2.94 13.60 13.70 9.56 0.16 9.58 2.63 0.59 0.34 0.29 100.99 300 370 89 301 128 20 9 448 179 31 20 112 15 35 8

C-198899 K207-22 Massive pillow basalt, 2440 mbsl 47.90 3.48 14.80 12.90 5.85 0.16 10.70 2.89 0.68 0.38 0.58 100.32 322 146 81 80 131 22 10 504 206 33 21 129 15 39 10

C-198900 K207-23 Basaltic pillow fragment, 2410 mbsl 50.30 2.66 13.20 12.60 8.01 0.17 10.90 2.25 0.45 0.29 �0.12 100.71 308 492 128 147 115 21 7 349 164 29 16 106 12 31 8

C-198901 K207-24 Crystalline basalt, 2307 mbsl 46.80 2.82 13.70 13.50 10.80 0.16 9.55 2.53 0.47 0.30 �0.24 100.39 255 411 102 369 128 26 6 460 165 26 17 107 12 30 10

C-198902 K207-25 Pillow frag., olivine basalt, 2137 mbsl 47.70 2.06 11.10 12.20 14.50 0.17 9.16 1.84 0.34 0.23 0.64 99.94 282 1180 111 647 109 19 4 252 119 23 13 59 12 26 7

C-198903 K207-28 Basaltic pillow fragment, 2137 mbsl 48.90 2.07 11.30 12.30 13.60 0.17 9.21 1.87 0.35 0.23 0.08 100.08 289 1200 102 518 103 15 7 247 125 25 12 75 9 22 10

Pillow-lava rib

C-198904 K208-2A Near-aphyric pillow basalt, 2539 mbsl 47.80 3.58 13.70 13.70 5.63 0.18 10.60 2.78 0.82 0.41 0.95 100.15 349 63 105 55 122 25 13 499 229 37 24 170 15 43 26

C-198905 K208-3 Fine-grained pillow basalt, 2515 mbsl 48.10 3.52 14.00 13.60 5.60 0.18 10.70 2.81 0.80 0.40 0.88 100.59 344 61 104 48 132 26 15 511 226 40 25 166 17 46 10

C-198906 K208-4 Near-aphyric pillow basalt, 2495 mbsl 48.30 3.56 14.00 13.70 5.41 0.18 10.80 2.81 0.78 0.41 0.61 100.56 338 60 123 51 131 25 13 513 223 35 23 176 18 44 15

C-198907 K208-5B Near-aphyric pillow basalt, 2472 mbsl 47.80 3.50 13.80 13.80 5.87 0.18 10.60 2.77 0.73 0.40 0.86 100.31 333 62 111 52 123 22 11 501 217 34 24 164 17 42 23

C-198908 K208-7 Fine-grained pillow basalt, 2372 mbsl 45.90 3.92 14.50 14.90 5.87 0.18 10.20 2.86 0.77 0.40 1.00 100.50 354 117 65 54 131 23 12 496 216 35 23 147 17 43 15

C-198909 K208-8 Near-aphyric pillow basalt, 2347 mbsl 46.10 3.92 14.50 14.80 6.00 0.18 10.20 2.83 0.78 0.40 0.69 100.40 366 124 61 53 131 22 12 493 214 33 23 148 16 40 27

C-198910 K208-9 Near-aphyric pillow basalt, 2243 mbsl 47.50 3.23 14.20 13.10 6.26 0.17 11.00 2.69 0.71 0.39 0.66 99.91 321 135 99 77 122 22 11 503 201 32 22 158 16 40 21

C-198911 K208-11 Near-aphyric pillow basalt, 2204 mbsl 47.20 3.42 14.20 13.10 6.24 0.17 11.20 2.70 0.73 0.40 0.82 100.18 330 199 97 74 124 20 11 541 206 34 23 160 13 40 15

C-198912 K208-14 Near-aphyric pillow basalt, 2080 mbsl 47.60 3.27 14.30 13.00 6.18 0.17 11.10 2.69 0.74 0.38 0.72 100.15 308 132 108 86 122 22 12 508 201 35 23 159 18 41 21

P.W.Lipmanet

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78

Papa‘u Seamount (breccia blocks)

C-198913 K209-4A Picrite with plagioclase, 1457 mbsl 48.90 1.68 10.90 12.10 15.30 0.17 8.62 1.79 0.26 0.21 �0.15 99.78 252 960 112 669 101 17 4 229 95 21 8 50 8 16 8

C-198914 K209-4B Fine-grained vuggy basalt, 1457 mbsl 52.10 2.06 13.90 11.50 7.19 0.16 11.10 2.26 0.30 0.23 �0.27 100.53 288 395 143 97 101 19 5 285 112 24 9 61 9 18 12

C-198915 K209-6A Olivine-plagioclase basalt, 1329 mbsl 50.60 2.12 13.80 12.20 7.96 0.17 10.90 2.30 0.29 0.24 �0.28 100.30 331 423 113 113 101 21 5 251 125 29 9 59 8 21 b7

C-198916 K209-6B Olivine-plagioclase basalt, 1329 mbsl 50.60 1.97 13.20 11.90 9.11 0.17 10.30 2.15 0.31 0.23 �0.19 99.75 294 685 127 225 101 15 5 270 114 26 10 61 9 20 12

C-198917 K209-8A Olivine basalt, 1146 mbsl 48.90 1.77 10.90 12.10 15.50 0.17 8.91 1.79 0.28 0.21 �0.26 100.27 262 1040 122 741 105 16 5 241 104 22 10 61 10 16 b7

C-198918 K209-12B Olivine-plagioclase basalt, 888 mbsl 50.80 1.93 12.90 12.30 9.79 0.17 10.20 2.08 0.32 0.22 �0.06 100.65 290 735 128 248 107 19 5 266 109 23 8 63 9 22 b7

C-198919 K209-13A Aphyric basal, 888 mbsl 51.50 2.26 13.70 12.10 7.26 0.17 10.40 2.38 0.38 0.26 �0.14 100.27 329 328 128 104 110 20 6 291 138 28 10 72 13 28 12

2002 dives

Hilina lower scarp (breccia clasts)

C-210375 S708-R6 Aphanitic basalt D =3175 m 44.90 4.18 15.60 13.40 4.23 0.17 8.68 4.88 1.63 0.98 0.06 98.71 202 b5 21 14 145 23 30 1130 491 57 56 417 40 100 61

C-210376 S708-RU1 Aphanitic pillow fragment D =3175 m 44.50 4.20 15.70 12.60 3.89 0.17 8.72 4.87 1.75 0.97 1.83 99.20 234 b5 18 18 145 25 29 1110 500 55 56 427 39 97 56

Pillow-lava rib

C-210377 S709-R1 Vuggy small-pl basalt, D =2048 m 45.50 3.92 14.80 14.60 5.41 0.17 10.40 2.92 0.69 0.39 1.34 100.14 368 127 70 54 128 25 10 504 210 34 23 148 18 44 19

C-210378 S709-R3 Finely vesicular basalt D =2036 m 45.50 3.95 14.30 15.00 6.04 0.18 10.20 2.84 0.65 0.38 0.51 99.55 355 113 71 55 128 23 9 492 213 35 23 159 17 41 24

C-210379 S709-R4 Acicular-pl basalt D =2012 m 46.60 3.42 14.10 12.80 6.33 0.19 11.30 2.70 0.71 0.39 0.88 99.42 330 220 75 84 121 16 10 540 206 33 24 165 20 44 23

C-210380 S709-R5 Aphanitic basalt D =1965 m 46.60 4.00 14.40 12.90 5.52 0.18 10.60 3.21 0.90 0.50 0.51 99.32 355 83 68 65 120 21 10 636 265 38 30 217 22 51 28

C-210381 S709-R6B Vuggy small-pl basalt D =1868 m 46.30 4.00 14.30 13.20 5.39 0.21 10.40 3.21 0.95 0.50 0.96 99.42 364 91 106 73 129 26 13 626 264 37 29 211 20 52 32

C-210382 S709-R9 Olivine basalt pillow fragment D =1821 m 44.20 4.68 13.80 14.60 6.75 0.19 11.40 2.39 0.53 0.30 0.57 99.41 412 199 133 128 125 24 7 444 191 33 20 123 17 38 12

SW Hilina bcornerQ (breccia clasts)

C-210383 S710-R1 Dense aphanitic basalt D =4401 m 45.00 2.52 12.30 12.50 9.30 0.17 14.30 2.24 0.64 0.30 0.11 99.38 457 465 154 175 101 19 13 398 131 23 21 180 16 38 b10

C-210384 S710-R2A Olivine basalt D =4367 m 49.00 2.02 12.50 12.10 10.20 0.16 10.10 2.12 0.29 0.24 1.00 99.73 313 763 131 270 110 18 4 261 115 24 11 53 10 21 11

C-210385 S710-R2C Olivine basalt D =4367 m 49.00 2.66 13.30 12.10 8.20 0.16 11.00 2.52 0.56 0.37 �0.03 99.84 328 463 111 182 113 22 9 432 169 26 19 133 18 39 24

C-210386 S710-R3E Aphanitic basalt D =4121 m 50.20 2.14 13.20 12.10 8.22 0.17 10.70 2.22 0.33 0.23 �0.16 99.35 316 532 127 157 109 20 5 283 122 23 10 74 9 25 b10

C-210387 S710-R4C Apahnitic dense basalt D =4122 m 49.90 2.19 13.50 12.00 7.91 0.17 11.10 2.25 0.34 0.27 0.08 99.71 330 413 128 133 102 21 5 301 124 25 11 70 13 25 b10

C-210388 S710-R4D Vesciular black pahoehoe D =4122 m 49.90 2.14 13.60 12.40 7.37 0.17 10.40 2.21 0.20 0.20 1.13 99.72 311 351 100 86 99 17 2 274 121 23 10 53 9 21 b10

C-210389 S710-R5x Dense aphanitic basalt D =4032 m 51.10 2.07 13.70 12.30 7.09 0.17 10.70 2.28 0.32 0.23 �0.11 99.85 318 334 125 77 103 18 6 276 118 26 10 61 7 16 b10

C-210390 S710-R7A Vesicular black pahoehoe D =3886 m 49.70 2.23 12.90 11.70 9.48 0.16 10.70 2.18 0.36 0.25 �0.01 99.65 333 745 120 273 109 20 6 309 125 24 12 78 11 25 20

C-210391 S710-R7D Vesicular black pahoehoe D =3886 m 50.20 2.11 12.90 12.20 9.02 0.17 10.40 2.24 0.28 0.23 �0.09 99.66 309 566 73 186 100 20 4 277 116 24 10 64 11 14 b10

P.W.Lipmanet

al./JournalofVolca

nologyandGeotherm

alResea

rch151(2006)73–108

79

steep lower scarp (averages 25 degrees overall; some

segments near vertical) descends 2000 m to the base of

the island at about �5000 m. The lower scarp is fluted

and embayed with a morphology suggestive of small

landslide scars, and an alluvial-appearing apron and a

few large elongate outlying blocks provide a record of

mass wasting from these scarps (Smith et al., 1999;

Lipman et al., 2002; Leslie et al., 2002). To the south-

west, the mid-slope bench is bounded by a linear

transverse scarp trending to the northwest, with a high

point at Papa‘u Seamount (Fig. 2). To the northeast the

bench narrows and merges with the south flank of the

Puna Ridge.

Prior to inception of the Japan–USA collaborative

studies of the underwater flanks of Hawaiian volcanoes

in 1998, no dive observations, deep photography, or

dredging had been undertaken on the submarine south

flank of Kılauea. Direct observations by observers in

the manned Shinkai 6500, video and still-camera

images, and samples collected during 16 dives have

now provided voluminous data leading to insights

concerning the ancestral growth of Kılauea. Major

recent observations (Lipman et al., 2000, 2002; Sisson

et al., 2002; Naka et al., 2002; Kimura et al., 2006-this

issue; Coombs et al., 2006-this issue) include: (1) all

outcrops on the lower scarp are volcaniclastic rocks; (2)

pillow-lava sequences form bedrock of the upper slope;

(3) breccia-clast and pillow compositions in both areas

are diverse submarine-erupted alkalic and transitional

basalts, without tholeiite of present-day Kılauea com-

position; (4) a voluminous component of tholeiitic sand

in the volcaniclastic rocks was derived from subaerial

Mauna Loa and probably Mauna Kea; (5) geochrono-

logic determinations indicate unexpectedly young ages

for early growth of ancestral Kılauea. These results are

summarized briefly below to document the ancestral

submarine growth of Kılauea and to provide a frame-

work for interpretations in this paper.

3.1. Volcaniclastic rocks on the lower scarp

Eight dives at widely distributed sites on the lower

scarp (Fig. 2) encountered thick sections of volcaniclas-

tic rocks, without interlayered pillow lavas or other

primary volcanic deposits (Lipman et al., 2002; Coombs

et al., 2006-this issue). The dominant volcaniclastic

rocks are coarse debris-flow breccia, interbeded with

indurated sandstone beds consisting dominantly of well-

sorted basaltic glass. Bedding in the volcaniclastic se-

quence dips gently, but fractures and shears indicate

deformation, presumably compression during uplift of

the bench to form the closed basin behind it. The

assemblage of volcaniclastic rocks has been interpreted

as recurrently emplaced debris-flow and turbidite

deposits derived from the ancestral submarine Kılauea

edifice, along with coastal detritus from older volcanoes

of Hawai‘i Island (Mauna Loa, Mauna Kea).

3.2. Pillow lavas above and east of the mid-slope bench

Rock ribs that project through the weakly consoli-

dated sediment mantle on slopes above the bench ex-

pose cliff outcrops of massive pillow lava, as traversed

by four dives (K95, K208, S504, S709). An 800-m high

outcropping rib, exposed and sampled at depths of

�2600 to �1800 m (dives K208, S709), consists of

weakly alkalic pillow basalt (Coombs et al., 2006-this

issue; Kimura et al., 2006-this issue). Along the east

margin of the mid-slope bench and up slope, offshore

from the proximal east rift zone, two dives (dives K95,

S504) traversed a similar thick pillow-lava sequence

(�3700 to �2900 m) of uniform transitional basalt

(Sisson et al., 2002). All large outcrops at these

upper-slope sites are truncated pillows; primary depo-

sitional surfaces have been disrupted by slumping or

landsliding along steep slopes. Such outcrops thus ex-

pose sections through the primary constructional edifice

of submarine Kılauea, rather than drapes of pillow lava

that mantle pre-existing steep slopes. Bedded volcani-

clastic sediments are nearly absent (a few beds 1–2 m

thick were encountered near the top of dive S709), in

contrast to the clastic sequence on the lower scarp.

3.3. Compositions of submarine south-flank lavas and

clasts

Nearly all clasts from breccias on the lower scarp and

pillow lavas from the upper slope are diverse alkalic and

transitional basalts (Table 1; Fig. 3). Almost all clast and

pillow samples with preserved glass rinds have substan-

tial S, CO2, and H2O contents suggestive of submarine

eruption at depths of as much as several kilometers

(Coombs et al., 2006-this issue). Sampled clasts have

diverse alkalic melt compositions, including rare neph-

elinite with SiO2 as low as 38% and phonotephrite with

as much as 9% total alkalis (Lipman et al., 2002, Fig. 7;

Sisson et al., 2002, Table 2). The observed composi-

tional range of this suite, interpreted as representing the

early pre-shield growth of Kılauea, is far more diverse

than at Lo‘ihi Seamount (Moore et al., 1982; Garcia et

al., 1995a), and includes alkalic magma types unknown

from elsewhere on Hawai‘i Island. Proportions of highly

alkalic clasts show a general upward decrease as abun-

dance of transitional basalt increases (Lipman et al.,

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10880

2002, Fig. 6). No obvious reversal or repetitions were

detected, suggesting that the lower scarp section is

largely structurally coherent, although the volcaniclastic

nature of these deposits precludes assigning detailed

stratigraphic significance to the succession of clast com-

positions. A few vesicular clasts, having distinct Loa-

type compositions (in contrast to Kea-type—e.g., lower

SiO2, higher TiO2 and alkalis, associated trace-element

variations: Wright, 1971; Jackson et al., 1972; Garcia et

al., 1995b; Rhodes, 1996), are inferred to have been

derived from the subaerial Mauna Loa edifice at the time

of growth of ancestral Kılauea.

Samples from the pillow rib above the central mid-

slope bench (dives K208, S709), have high volatile

contents and uniform weakly alkalic compositions

(Coombs et al., 2006-this issue; Kimura et al., 2006-

this issue). A similarly thick sequence of higher-SiO2

transitional-composition pillow lavas at the east end of

the mid-slope bench (dives K98, S504) are also volatile

rich and therefore submarine erupted, and plot within

the tholeiite field, but are well removed in composition

from present-day Kılauea lavas. No in-place outcrops of

highly alkalic pillow lavas (basanite, phonotephrite,

nephelinite) were sampled; clasts in the lower-scarp

breccias with these compositions therefore are inter-

preted as derived from older deeper parts of the ances-

tral Kılauea edifice, now buried beneath the weakly

alkalic and transitional lavas.

A single pillow lava sample from the mid-slope

bench (S504-R5) is degassed and has a composition

similar to present-day Kılauea flows (Fig. 3); this is

interpreted as a late slope-draping flow (Lipman et al.,

2002), a lone exception to all other in-place samples of

pillow lava. Only one recovered clast, from a breccia

above the mid-slope bench (K207-R23), has a compo-

sition similar to present-day Kılauea tholeiite (Table 1;

Coombs et al., 2006-this issue), indicating that no

sizable shield-stage collapse occurred during the main

accumulation of volcaniclastic deposits underlying the

mid-slope bench. The scarcity of Kılauea-type tholeiite,

either as lavas or clasts from the summit and proximal

rifts of this volcano, is striking, especially in compar-

ison with the well-sampled upper submarine flank of

Mauna Loa in South Kona, which is draped by shore-

line-crossing degassed pillow lavas (Garcia and Davis,

2001; Morgan and Clague, 2003; Yokose and Lipman,

2004).

3.4. Sandstones and breccia matrix

Turbidite sandstones and matrix of breccias on the

lower scarp consist dominantly of low-S tholeiitic glass

derived from subaerially erupted lava flows that crossed

the shoreline; both Kea and Loa compositional types

are present. Such sand is a major component of the

lower-scarp sections, overall at least 50% by volume.

Grains of mafic alkalic glass, with compositions

encompassing but even more diverse than the breccia

clasts (Sisson et al., 2002, 2003), are sparsely scattered

through most sandstones and the matrix of breccias.

Alkalic grains are abundant in a few sandstone samples,

especially low along the lower scarp and the rare sand-

Fig. 3. Alkali–silica diagram, basaltic pillow lavas and breccia clasts, from dive sites (in parentheses) in Hilina slump area. Dashed lines, IUGG rock

classification, and boundary between tholeiite and alkalic basalt (Macdonald and Katsura, 1964). Data for Hilina flank are from Tables 1 and 2,

Sisson et al. (2002), and Coombs et al. (2006-this issue); Puna Ridge analyses are from Clague et al. (1995). Compositions of some extremely

alkalic clasts (nephelinite, phonotephrite: Lipman et al., 2002, Fig. 7) plot outside the figure area.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 81

stones exposed in the upper-slope alkalic pillow rib.

Nearly all of the highly alkalic sand grains are high S

(N400 ppm), in contrast to the tholeiitic glass grains

that overwhelmingly have low volatile concentrations

indicative of subaerial degassing (Sisson et al., 2002,

fig. 2; Coombs et al., 2006-this issue, fig. 4). Compo-

sitionally and petrogenetically coherent suites of alkalic

glass grains are present in some sandstone samples

(Sisson, 2003), indicating that those alkalic grains

were of local origin and were not transported long

distances by littoral processes.

3.5. Ar–Ar ages of south flank basalts

Tholeiitic Hawaiian basalts generally have been dif-

ficult to date by K–Ar or Ar–Ar methods because of

low potassium contents, excess radiogenic Ar derived

from magma generation in the mantle (e.g., Dalrymple

and Moore, 1968; Lipman et al., 1990), and the mobil-

ity of potassium due to the location of this element in

glass or weakly devitrified matrix (Lipman et al., 1990;

Teanby et al., 2002). The south-flank breccia clasts and

pillow lavas of alkalic composition have higher K

contents and have yielded a coherent suite of incremen-

tal heating 40Ar–39Ar ages (13 samples dated), ranging

from 280 to 125 ka (Calvert and Lanphere, 2006-this

issue). The most alkalic clasts, from low along the

lower scarp, have the oldest ages (Fig. 4); especially

analytically well constrained are mica ages of 235–240

ka, from two clasts of phlogopite-bearing nephelinite.

In contrast, five samples of in-place weakly alkalic

basalt from the pillow rib at water depths of �2400

to �1800 m above the mid-slope bench yielded coher-

ent ages of 140–165 ka. Two difficult-to-date transi-

tional pillow samples yielded ages of 230 and 140 ka,

necessarily with large analytical uncertainties (~F50

ka, F1r). Thus, at least the bulk of shield-stage tho-

leiitic eruptions at Kılauea were probably younger than

150 ka, probably less than 100 ka.

Overall, in conjunction with recognition of thick

submarine sections of alkalic and transitional pillows,

the new 40Ar–39Ar results suggest probable approxi-

mate time spans (likely uncertainty, F25 ka) for dom-

inant eruption of the compositional sequence: diverse

early alkalic, 275–200 ka; late weakly alkalic, 200–150

ka; transitional, 150–100 ka; tholeiitic, 100 ka-continu-

ing. Ages as old as 436 ka, reported for present-day-

type Kılauea tholeiites from drill holes along the middle

east rift zone (Guillou et al., 1997; Quane et al., 2000),

are inconsistent with the simple covariation of ages,

compositions, and geologic setting of the submarine

Kılauea samples. The reported ages for the drill-hole

tholeiites may be erroneous, perhaps due to excess

radiogenic Ar.

4. Mauna Loa and its south flank structure

Mauna Loa is a larger and older volcano than

Kılauea, but these two volcanoes have similar gross

geometries, with a summit caldera, opposed arcuate

rift zones, and a steep south flank that lacks eruptive

vents (Stearns and Macdonald, 1946; Wolfe and Morris,

Fig. 4. Summary of interpreted ages for events related to growth of Kılauea Volcano. Data sources: 1. Radiocarbon (Beeson et al., 1996); 2. Ar–Ar

(Lipman et al., 2002; Calvert and Lanphere, 2006-this issue); 3. Sedimentation rate (Naka et al., 2002); 4. Ar–Ar (Sharp et al., 1996); 5. Unspiked

K–Ar, SOH hole (Guillou et al., 1997).

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10882

1996). In contrast to Kılauea, the north to west flanks of

Mauna Loa contain scattered radial vents (Lockwood

and Lipman, 1987). Like Kılauea, the summit of Mauna

Loa is associated with a large positive Bouguer gravity

anomaly, evidence of dense intrusive and cumulate

rocks at depth. This anomaly extends farther seaward

(~ 20 km), and asymmetrically southeast of the summit

caldera, than the anomaly at Kılauea (~10 km across)

centered on the caldera (Kauahikaua, 1993; Kauahikaua

et al., 2000), suggesting more intense lateral seaward

spreading at Mauna Loa.

4.1. Eruptive history

Overall, individual historical Mauna Loa eruptions

have been less frequent, but larger in volume than those

on Kılauea. Typical eruptive cycles have sequentially

involved a brief summit eruption, followed within

months to a few years by a longer-duration rift eruption

(Stearns and Macdonald, 1946, p. 79; Macdonald and

Abbott, 1970, p. 55; Lockwood et al., 1987). Most

historical rift-zone and radial-vent eruptions have

been relatively brief in duration (a few weeks to

months) but with high discharge rates that favor distal

emplacement of lava as a‘a rather than pahoehoe.

Some evidence suggests that Mauna Loa reached

approximately its present size before 100 ka, and that

its rate of growth as a tholeiitic shield has since been

declining (Lipman, 1995). Historical behavior of

Mauna Loa has varied greatly, with frequent eruptions

(avg. ~every 3.6 yr) from initial records in the early

19th century up through 1950 (Stearns and Macdonald,

1946; Macdonald and Abbott, 1970). In the half century

since 1950, however, only a single summit-rift eruptive

cycle has occurred (1975–84: Lockwood et al., 1987).

Geologic mapping and radiocarbon dating have provid-

ed a longer-term perspective on eruptive activity, which

suggests that the early historical period was a time of

atypically high eruptive activity at Mauna Loa, at least

relative to the past few thousand years (Lipman, 1980a;

Lockwood, 1995).

Several structures on the south flank of Mauna

Loa hint of an earlier growth history more closely

akin to that characterizing present-day Kılauea: (1)

the Kao‘iki–Wai‘ohinu fault system as a now-weakly-

active counterpart to the Hilina system on Kılauea;

(2) continuing south-flank deformation and seismicity

on Mauna Loa in addition to that at Kılauea, indicat-

ing that more than the south flank of Kılauea is

involved the overall active tectonics of Hawai‘i Is-

land; (3) a large-scale landslide (Punalu‘u slump)

prior to growth of Kılauea, suggesting that volcani-

clastic Mauna Loa rocks underlie the Hilina Bench.

Submersible observations along the southwest margin

of the Hilina mid-slope bench now confirm that

Mauna Loa was a large subaerial tholeiitic shield

prior to initial growth of Kılauea.

4.2. Kaodiki–Honudapo fault system

The Kao‘iki–Honu‘apo fault system is a northeast-

trending zone of lava-draped fault scarps and fractures

traceable, at elevations from sea level to 1800 m, for

50 km along the south flank of Mauna Loa (Stearns

and Macdonald, 1946; Wolfe and Morris, 1996). The

largest remnant scarps, in the Ninole Hills area, are as

high as 200 m. Fault scarps indicate dominant sea-

ward-down displacements, but amounts of offset at

many sites are difficult to estimate because of cover-

age by younger Mauna Loa lava flows. Some flows

draping scarps are as old as 9.8 ka, without obvious

offset (Lipman, 1980b; Rubin et al., 1987; Lipman et

al., 1990), but the fault zone is a locus of continuing

seismicity (Endo, 1985; Klein et al., 1987; Jackson et

al., 1992). It has been inferred, at least since Stearns

and Clark (1930, p. 96–97), that the Kao‘iki–Hon-

u‘apo faults represent a nearly inactive counterpart

on Mauna Loa to the Hilina system on Kılauea (Lip-

man et al., 1990).

4.3. South-flank deformation on Mauna Loa

High levels of deformation and seismicity have been

recorded at Kılauea throughout the past half century,

since the advent of instrumental monitoring. Under-

standing of analogous activity on Mauna Loa has

lagged, both because of the relative quiescence of this

volcano since the large southwest rift eruption in 1950

and because the size and inaccessibility of upper parts

of this enormous edifice have drastically impeded de-

tailed geophysical measurements. For example, after

the 1975 summit eruptions, a substantial effort was

made by staff of the Hawaiian Volcano Observatory

to augment the seismic stations and to establish defor-

mation networks (trilateration by EDM, some leveling)

along the rift zones and south flank of Mauna Loa.

These networks provided improved resolution during

the 1984 northeast rift eruption and precursor events

Lockwood et al., 1987). Deformation measurements by

EDM nicely tracked precursor summit inflation and

extension along the northeast rift that accompanied

dike intrusion as magma flowed to the eruptive vent

(Lockwood et al., 1987). In contrast, the vast size and

curvature of the Mauna Loa shield precluded measure-

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 83

ments on flanks in detail comparable to those routinely

obtained at Kılauea.

Through the 1980s, most EDM surveys were insuf-

ficiently robust, and inadequately referenced to stable

areas of Hawai‘i Island, to permit resolution of small

displacements (cm-scale) across the south flank of

Mauna Loa and the degree to which deformation high

on this edifice was accommodated by adjacent Kılauea.

In association with the M =7.2 Kalapana earthquake in

1975, however, displacement solutions for trilateration

stations low on the south flank of Mauna Loa all show

seaward motions of 0.4 to as much as 1.2 m, even

though the three most distal stations were arbitrarily

held as fixed to provide reference points for the geo-

detic network (Lipman et al., 1985).

Since 1990, geodetic monitoring by GPS has made it

possible routinely to resolve cm-scale displacements on

the flanks of Mauna Loa (Miklius et al., 1995). The first

decade of observations, while still a brief interval,

defines a consistent pattern of small seaward motions

on the south flank. Horizontal displacements increase in

amplitude down slope, from largely below instrumental

delectability at high elevations, to about 1–1.5 cm/yr

adjacent to the boundary with Kılauea (Fig. 5; Owen et

al., 2000; Miklius et al., in press). Thus, despite growth

of Kılauea, currently at rates that are substantially more

vigorous than for Mauna Loa (Lipman, 1995; DePaolo

and Stolper, 1996; DePaolo et al., 2001), prehistoric

displacements along Kao‘iki–Honu‘apo faults, deforma-

tion during the large 1868 and 1975 earthquakes, and

recent GPS determinations all document persistent sea-

ward displacement of Mauna Loa’s lower south flank.

On both volcanoes, near-summit and rift-zone dis-

placements are strongly influenced by inflation/defla-

tion of their magma chambers and dike intrusion along

rift zones (Swanson et al., 1976; Duffield et al., 1982;

Dvorak et al., 1986). In contrast, the regional pattern of

horizontal deformation shows sustained seaward dis-

placements that progressively increase down the south

flank of Hawai‘i Island, seemingly independent of the

surface boundary between the two volcanoes (Fig. 5).

Some dislocation models have been used to infer that

the motions on Mauna Loa are shallow secondary

responses to displacements bounded at depth by

Kılauea’s rift zones (Owen et al., 2000), but such

interpretations seem inconsistent with the broad distri-

bution of earthquakes beneath Mauna Loa’s south

flank, as discussed below.

4.4. Seismicity on Mauna Loa

In addition to eruption-related earthquakes concen-

trated at the summit of Mauna Loa and along its rift

zones, the entire south side of Hawai‘i Island is charac-

terized by broad diffuse levels of seismicity. The south

flank of Mauna Loa is marked by frequent small and

intermittent large earthquakes (including M =5.5 in

1974 and M =6.6 in 1983); these are commonly

known as Kao‘iki earthquakes, although most occur

upslope from the surface Kao‘iki fault zone (Fig. 6).

Fig. 5. Horizontal displacements determined by GPS, south flank of Hawai‘i Island, 1998–2003 (Miklius et al., in press). Vectors (average

horizontal velocities per year) show gradual increase in displacement down the south flank of Hawai‘i Island, without discontinuity at surface

boundary between volcanoes. Note that displacements on the lower south flank of Mauna Loa are larger than those associated with its summit

magma reservoir. Prior to 1998, GPS coverage was more limited for the Mauna Loa edifice, but the vector geometry was similar (Owen et al., 2000).

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10884

Fig. 6. South flank seismicity. A. Interpreted slip directions for Kao‘iki earthquakes, recorded between 1959 and 1982 (Endo, 1985; Jackson et al.,

1992). Upward-pointing triangles are seismic stations. (1) Slip directions from strike-slip focal mechanisms: NE–SW-striking surface is assumed to

be the nodal plane. Arrows show right-lateral displacement of the seaward fault block. (2) Slip directions from low-angle thrust focal mechanisms;

gently NW-dipping surface is assumed to be the nodal plane. Arrows show seaward displacement of the upper fault block. B. Map of seismicity

(1970–1983) on Kılauea and Mauna Loa (after Klein et al., 1987, fig. 43.17). All earthquakes within rectangle are plotted on line of section. Deep

hypocenters (15–40 km define separate magma conduits for Kılauea and Mauna Loa volcanoes. Gently dipping base of intense seismicity is

interpreted as contact between volcanic edifice and underlying oceanic crust, consistent with the location of this boundary as determined by seismic

refraction profiling (Hill and Zucca, 1987). Absence of any apparent seismic discontinuity between Kılauea and Mauna Loa suggests that the flank

of Hawai‘i Island is involved in south-slope deformation. C. Cross-section of seismicity (1970–1983) on Kılauea and Mauna Loa (after Klein et al.,

1987, fig. 43.17). Diagonal dashed line, surface boundary between volcanoes.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 85

First-motion solutions for Kao‘iki earthquakes (Fig.

6-A) have two divergent geometries (Endo, 1985; Jack-

son et al., 1992; Got and Okubo, 2003): (1) left-lateral

strike slip, trending northeast, parallel to the Kao‘iki

fault zone; and (2) southeast-trending low-angle thrust,

similar to orientations for large deep decollement earth-

quakes on Kılauea, such as the 1975 Kalapana event

(Ando, 1979; Crosson and Endo, 1982). Strike-slip

events may accommodate differential motions between

the Kılauea and Mauna Loa magmatic systems along

Kao‘iki faults. Thrust events are likely associated with

the seaward spreading of the Mauna Loa south flank, as

recorded by GPS displacements and geometrically con-

sistent with displacements during the 1975 Kalapana

earthquake measured by trilateration.

Additional seismic evidence for recent mobility of

Mauna Loa’s south flank is provided by the 1868

M =~8 earthquake (Brigham, 1909; Wood, 1914),

which appears to have been similar in rupture geometry

to the 1975 Kalapana quake, involving low-angle sea-

ward slip at the base of the volcanic pile (Wyss, 1988).

This largest historical earthquake on Hawai‘i Island

appears to have been centered on the south flank of

Mauna Loa, in contrast to the Kılauea locus of the 1975

Kalapana quake. Lateral motions appear to have been

dominant, with horizontal displacements along the

Wai’ohinu tear fault (Fig. 1) of as much as 2–3 m

(Hitchcock, 1909, p. 105–106; Wood, 1914; Lipman,

1980a), accompanied by widespread coastal subsidence

(Brigham, 1909).

Plotted in cross-section, earthquakes on Hawai‘i

Island define a continuous diffuse band across Kılauea

and the south flank of Mauna Loa, with depth gradu-

ally increasing inland (e.g., Klein et al., 1987, fig.

43.17 for time interval 1970–83; Denlinger and

Okubo, 1995, fig. 5—relocated for time interval

1970–89). The deepest earthquake hypocenters, in-

creasing landward from about 9 km below the coastline

to 12 km below upper slopes of Mauna Loa (Fig.

6B,C), coincide closely with the base of the volcanic

edifice as determined independently by seismic-refrac-

tion profiling (Hill and Zucca, 1987; Thurber and Li,

1989). When a subset of earthquakes below the upper

flank of Kılauea were relocated more precisely by

relative-muliplet methods (Got et al., 1994; Got and

Okubo, 2003), the cloud of hypocenters collapses to

define a plane dipping about 68 northwestward at the

base of the volcanic pile, compatible with slip along a

bounding decollement fault. Even within the area stud-

ied by Got et al. (1994), this fault likely separates the

south flank of Mauna Loa, beneath the Kılauea edifice

as discussed in a later section, from the underlying

oceanic crust. Thus, the combined seismic and defor-

mation data are consistent with processes of seaward

gravitational spreading of the entire south flank of

Hawai‘i Island, encompassing the edifices of both

Mauna Loa and Kılauea, largely occurring along a

basal decollement at the boundary between old seafloor

and the volcanic pile.

4.5. Punalu‘u slump and underwater south flank

The volcanoes of Hawai‘i Island are surrounded by

large submarine landslides (Moore, 1964; Lipman et

al., 1988; Moore et al., 1989). Existence of the Puna-

lu‘u slump south of Mauna Loa was originally inferred

on the basis of seaward truncation of structurally high

erosional remnants of old Mauna Loa rocks on the

subaerial south flank (Ninole Hills) and limited ba-

thymetry and side-scan sonar for adjacent underwater

areas (Lipman et al., 1990). High-resolution SeaBeam

bathymetry (Chadwick et al., 1993; J. Smith et al.,

2002; Eakins et al., 2003) now documents a mid-

slope bench west of Lo‘ihi Seamount with its outer

lip at about �2500 m (Figs. 1, 2). A steep lower scarp

descends to about �4000 m, below which a relatively

steep smooth fan of presumed slide debris merges with

the Cretaceous sea floor. An irregular slope above the

bench is probably mantled by post-slump shoreline-

crossing Mauna Loa lavas, and in part by flows from

the lower southwest rift zone of Kılauea, a structure

that has only modest morphologic expression underwa-

ter, especially compared to the Kılauea’s Puna Ridge

(Fig. 2).

Dive S507 with the Shinkai 6500 submersible tra-

versed the lower Punalu‘u scarp from �3500 to �2700

m. Other than one cliff-forming layer of relatively

crystalline aphyric tholeiite that may represent ponded

lava or a sill at �2750 m, the lower-scarp slope con-

sisted entirely of weakly indurated breccias, and all 10

collected samples were similar of olivine-rich (5–30%)

basalt fragments (Lipman et al., 2002, Appendix). All

analyzed samples (including those from the cliff-form-

ing aphyric basalt) are tholeiite compositionally similar

to young subaerial Mauna Loa lavas, and all large clasts

that preserve glassy margins are low S (30–300 ppm;

avg. 150 ppm: Sisson et al., 2002, Appendix), indica-

tive of subaerial eruption. No young-appearing lavas

were sampled that could have erupted from the Kılauea

southwest rift, nor do any of the analyzed samples have

Kılauea-like compositions.

Ocean-floor turbidites south of Hawai‘i Island (Naka

et al., 2002) also record a large landslide from this side

of Mauna Loa, as marked by a meter-thick layer of

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10886

tholeiitic glass sand with an age (interpolated from

sedimentation rates) of ~400 ka, older than any of the

newly determined 40Ar / 39Ar ages for ancestral alkalic

Kılauea. The basaltic sand in the turbidite layer is

compositionally similar to modern Mauna Loa tholeiite

glasses, with low S contents, indicating origin from

subaerial lava flows that were quenched and disaggre-

gated as they crossed the shoreline. This turbidite may

provide a distal record of emplacement of the Punalu‘u

slump at ~400 ka (Fig. 4). Such an age for this event,

implying existence of a sizable subaerial edifice, is

earlier than the 300-ka date estimated by Moore and

Clague (1992) for emergence of Mauna Loa above sea

level.

4.6. Mauna Loa rocks at southwest margin of Hilina

mid-slope bench

Two dives (K209, S710) along the southwest margin

of the Hilina bench, made late during the Japan–USA

research program, encountered massive debris-flow or

landslide breccias in which all clasts consist of subaer-

ially erupted a‘a and phoehoe of Loa-type compositions

(Figs. 3, 7).

Dive K209 ascended 940 m (�1680 to �740 m) up

the steep west slope of Papa‘u Seamount, along the

transverse scarp that bounds the Hilina mid-slope bench

(Coombs et al., 2006-this issue). All outcrops were

subtly bedded uniform-appearing breccia, and no

Kılauea-like compositions were found among the 24

clasts (Tables 1, 2). All the samples plot along an

olivine-control trend for Loa-type tholeiite (Fig. 3),

with higher SiO2 and lower alkalis and TiO2 at constant

MgO than equivalent Kılauea basalt. More than half the

samples are highly vesicular (10–30%), many with

round phoehoe-type bubble textures, some variably

oxidized. No in-place pillow lavas were observed, and

no submarine-erupted pillow fragments were sampled,

in contrast to clast suites from the lower Hilina scarp,

where pillow fragments are common. Seven breccia

clasts with glassy margins average only 70 ppm S

(range: 25–130 ppm); these could be pillow fragments

from subaerial lava that crossed the shoreline or from

subaerial phoehoe lobes. All the K209 samples thus

Fig. 7. Cross-section interpreting present-day geometry along transverse boundary scarp, from summit of Mauna Loa through Papa‘u Seamount.

Location shown on Fig. 10. Southwest flank of Kılauea is only a thin veneer, overlying the thick south slope of Mauna Loa, and the cross-sectional

area of primary volcanic rocks (pillow lavas) on this side of Kılauea is about the same as for volcaniclastic deposits. A. 5� vertical exaggeration. B.

No vertical exaggeration.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 87

Table 2

Compositions of breccia clasts, south flank of Papa‘u Seamount (analyses by J. Kimura at Shimane University)

Sample # XRF majors (wt.%) XRF trace elements (ppm)

SiO2 TiO2 Al2O3 FeO* MnO MgO CaO Na2O K2O P2O5 Total Sc V Cr Ni Ga Rb Sr Y Zr Nb Ba Ce

K209-1a 49.33 1.82 11.48 12.24 0.16 13.14 9.10 1.87 0.25 0.16 99.53 24.4 307 773 462 15.8 6.4 238 22.1 99 10.6 70 24

K209-1b 48.93 2.25 11.57 12.48 0.16 11.80 9.81 1.84 0.33 0.20 99.37 28.8 326 821 345 16.9 8.1 285 24.6 129 14.9 93 33

K209-2a 48.74 1.71 10.99 12.76 0.16 15.70 8.62 1.71 0.17 0.12 100.70 25.1 258 1093 592 16.2 4.8 213 18.8 88 8.8 50 15

K209-2b 51.03 2.11 13.36 12.35 0.16 8.18 10.62 2.21 0.30 0.17 100.48 28.4 329 334 119 19.9 5.4 263 26.0 110 10.1 63 25

K209-3a 50.58 2.03 13.47 12.25 0.16 7.55 10.60 2.28 0.23 0.18 99.32 30.0 348 263 102 18.2 6.5 245 31.1 116 10.4 67 22

K209-4a 49.21 1.69 10.89 11.86 0.15 15.11 8.57 1.72 0.23 0.16 99.57 24.0 273 796 624 15.0 6.9 224 21.2 92 9.9 66 15

K209-4b 51.60 2.08 13.60 11.79 0.16 7.47 11.05 2.22 0.27 0.18 100.40 29.1 343 377 111 19.7 5.6 272 25.9 108 10.4 68 23

K209-5a 50.06 2.29 13.37 12.28 0.16 7.58 10.84 2.26 0.32 0.21 99.37 29.6 352 332 102 18.6 7.9 296 27.4 125 12.1 76 21

K209-5b 50.00 2.13 12.70 12.46 0.16 9.22 10.14 2.13 0.29 0.19 99.41 29.9 333 435 170 18.2 7.3 281 24.3 116 12.2 72 21

K209-6a 49.98 2.09 13.20 12.35 0.16 8.12 10.49 2.22 0.25 0.19 99.04 31.4 348 319 120 18.3 6.3 243 29.2 118 10.3 71 16

K209-6b 50.46 1.95 12.67 12.18 0.16 9.52 10.00 2.06 0.26 0.17 99.43 26.8 323 531 222 16.9 7.1 257 24.3 108 10.2 71 21

K209-8a 48.55 1.69 10.43 11.89 0.15 16.44 8.42 1.59 0.22 0.15 99.53 23.4 282 862 734 15.1 6.3 226 21.0 94 10.3 70 15

K209-8b 50.34 1.95 12.56 12.57 0.16 10.44 10.05 2.08 0.25 0.17 100.56 29.5 313 608 250 17.6 6.0 248 25.1 104 9.7 66 17

K209-9a 51.08 2.18 13.45 12.48 0.16 7.32 10.82 2.22 0.41 0.19 100.31 29.4 345 359 106 5.3 8.0 277 25.7 118 12.8 73 29

K209-9b 51.10 2.07 13.37 11.91 0.15 7.37 10.57 2.15 0.32 0.18 99.20 29.5 328 351 107 18.3 8.2 275 24.2 113 12.0 72 26

K209-10a 50.50 1.72 14.22 11.05 0.15 7.82 11.35 2.06 0.22 0.15 99.23 30.7 283 279 102 17.7 7.2 246 22.8 91 10.5 69 18

K209-10b 50.39 1.93 12.02 11.29 0.15 11.70 9.61 1.89 0.24 0.17 99.37 26.5 311 668 439 17.7 5.9 253 24.0 105 10.8 73 25

K209-11 50.67 1.75 13.82 11.32 0.15 8.16 11.00 2.01 0.23 0.16 99.27 30.9 292 432 98 18.2 6.8 237 23.7 94 9.2 53 18

K209-12a 50.87 2.03 13.88 12.09 0.16 7.40 11.24 2.34 0.24 0.17 100.42 32.0 338 221 86 19.6 4.6 247 27.4 107 10.2 51 15

K209-12b 50.40 1.90 12.42 12.36 0.16 10.02 9.82 1.95 0.27 0.18 99.47 27.7 312 606 218 17.2 7.3 257 23.8 106 9.6 64 16

K209-12c 49.59 1.73 11.21 11.68 0.15 14.36 8.79 1.60 0.18 0.16 99.44 27.6 276 817 564 15.0 5.2 221 22.9 98 9.0 52 16

K209-13a 50.94 2.24 13.09 12.48 0.16 7.46 10.06 2.25 0.34 0.21 99.23 27.9 352 276 106 20.0 8.1 278 28.2 130 12.2 68 31

K209-13b 51.01 2.23 13.12 12.46 0.16 7.42 10.09 2.24 0.32 0.21 99.27 28.3 355 276 101 19.8 7.1 279 27.9 129 11.8 80 27

K209-13c 50.93 2.24 13.10 12.54 0.16 7.42 10.05 2.33 0.35 0.21 99.32 29.6 352 281 101 19.7 7.6 278 29.3 131 12.7 76 20

Sample ICP-MS analyses (ppm)

Li Be Rb Y Zr Nb Sb Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Tl Pb Th U

K209-1a 2.76 0.55 4.38 17.3 94 8.0 0.05 0.05 55 6.7 17.3 2.55 12.2 3.44 1.21 3.78 0.64 3.68 0.68 1.72 0.25 1.50 0.21 2.47 0.48 0.02 0.86 0.46 0.15

K209-2a 3.92 0.60 4.46 19.2 103 8.2 0.05 0.04 56 7.0 18.1 2.68 12.9 3.66 1.30 4.03 0.68 4.07 0.76 1.89 0.28 1.69 0.24 2.66 0.50 0.02 0.69 0.46 0.14

K209-3a 2.12 0.58 3.90 25.5 113 7.9 0.07 0.04 55 7.6 19.8 2.98 14.7 4.29 1.55 4.91 0.86 5.20 1.03 2.58 0.38 2.45 0.36 3.13 0.49 0.02 0.57 0.51 0.16

K209-4b 2.91 0.62 3.95 21.5 107 8.4 0.05 0.05 57 7.4 19.0 2.86 13.8 3.91 1.48 4.49 0.75 4.43 0.84 2.14 0.31 1.83 0.27 2.90 0.56 0.02 0.63 0.49 0.16

K209-5b 3.75 0.50 2.47 16.4 90 6.4 0.03 0.02 43 5.2 13.7 2.07 10.2 3.05 1.14 3.47 0.59 3.47 0.67 1.66 0.24 1.49 0.21 2.37 0.39 0.01 0.42 0.36 0.10

K209-8a 2.79 0.71 4.84 21.2 118 9.9 0.19 0.05 64 8.6 22.1 3.26 15.6 4.27 1.55 4.75 0.80 4.56 0.87 2.12 0.30 1.89 0.27 3.10 0.62 0.03 0.70 0.59 0.22

P.W.Lipmanet

al./JournalofVolca

nologyandGeotherm

alResea

rch151(2006)73–108

88

appear to have been derived from subaerial Mauna Loa.

Their compositions exclude prior interpretations of

Papa‘u as a debris flow or landslide from a shallow

embayment in KılaueaTs submarine flank (Fornari et al.,

1979; Morgan et al., 2003). Geometric relations be-

tween Papa‘u and volcaniclastic sequences on the

Hilina lower scarp, where most clasts came from an-

cestral alkalic Kılauea, are interpretable as involving

simple onlap of the Kılauea debris against the subma-

rine flank of Mauna Loa, along with uplift accompa-

nying formation of the Hilina bench, although more

elaborate tectonic reconstructions have been proposed

(e.g., Morgan et al., 2003).

A second dive (S710) traversed diverse breccias low

(�4430 to �3890 m) on the bcornerQ between the

Hilina lower scarp and transverse boundary structure

at depths of (Fig. 7). All breccia outcrops sampled

during this dive also have Loa-type compositions and

variably oxidized vesicular textures indicative of sub-

aerial origin. A few clasts, from a long talus run during a

middle segment of the dive (where outcrops were ab-

sent) are alkalic basalt similar to those sampled farther

northeast along the Hilina lower scarp. The alkalic clasts

may indicate interbeded Mauna Loa and early Kılauea

lithologies, but the talus samples could instead be en-

tirely from stratigraphically above the massive Loa-type

breccias sampled in outcrop. In either instance, the

preponderance of subaerial Mauna Loa clasts low at

the southwest end of the Hilina lower scarp section,

and constituting all of Papa‘u Seamount, are important

evidence showing that Mauna Loa’s flank broadly

underlies Kılauea. Inference of Mauna Loa rocks be-

neath the south flank of Kılauea is not new (e.g., Stearns

and Clark, 1930; Stearns and Macdonald, 1946, p. 132;

Swanson et al., 1976, fig. 16; Lipman et al., 1985, fig.

20; Moore and Chadwick, 1995, p. 22), but the dive

results provide the first observational confirmation for

such interpretations and also provide a geometric basis

for improved volume estimates for the volcanoes.

4.7. Volcano–tectonic interactions with Kilauea

A long-standing issue has been the extent of inter-

actions between Mauna Loa and Kılauea edifices, with

inferred consequences for seismicity, magma composi-

tion, deformation, and eruptive behavior. Among these

are: proposed interplay between locations of earth-

quakes and eruptibility at the two volcanoes (Klein,

1982; Jackson et al., 1992), petrogenetic significance

of rare overlaps in magma composition (Rhodes et al.,

1989; Garcia et al., 1995b), influence of gravitationally

induced stress on Mauna Loa’s south flank as controls

on the orientation of Kılauea’s rift zones (Fiske and

Jackson, 1972; Swanson et al., 1976), intertwined de-

formation responses on these adjacent volcanoes (Lip-

man et al., 1985; Miklius and Cervelli, 2003), and

effects of loading the older Mauna Loa flank by but-

tressing growth of the younger Kılauea, leading to

changed geometry of volcano spreading (Lipman,

1980b; Morgan, 2006-this issue).

Some studies have suggested that eruptive activity at

the two volcanoes could be either linked (e.g., Jagger,

1917), or antithetic with frequent large rift eruptions

from Mauna Loa prior to the 1950s, when Kılauea erup-

tions were mainly low-discharge activity within the cal-

dera, versus frequent Kılauea rift eruptions during the

last 50 years accompanied by much-reduced activity at

Mauna Loa (Stearns and Macdonald, 1946, p. 134;

Klein, 1982). A possible mechanism is that magma rise

and inflation at one edifice impedes similar behavior at

the other. Such processes also have the potential for

triggering synchronous behavior (Miklius and Cervelli,

2003). Within short time intervals, at least, behavior of

the two volcanoes can be largely independent; the 1984

rift eruption at Mauna Loa progressed to completion

without seemingly affecting the then-cyclic eruptive

behavior at Pu‘u ‘O‘o or producing any detectable inflec-

tions in seismic or geodetic records for stations on

Kılauea (Lockwood et al., 1987). In the discussion that

follows, we consider volcano–tectonic interactions be-

tween these two volcanoes through geologically long

intervals, focusing on implications of Kılauea’s growth

on the flank of an already large subaerial Mauna Loa.

5. Discussion

Collectively, published data for subaerial Kılauea

and Mauna Loa and recently acquired submarine obser-

vations on the south slope of Hawai‘i Island provide a

basis for new perspectives on the intertwined growth

histories of these two active volcanoes.

5.1. South flank of Mauna Loa during growth of

Kılauea

Continued eruptive activity and flank spreading on

Mauna Loa, after inception of Kılauea on the submarine

flank of the larger edifice, is here interpreted to have

strongly influenced the structural evolution and present-

day geometry of Kılauea.

5.1.1. Pre-Kılauea edifice of Mauna Loa

Prior to the birth of Kılauea, the south-flank struc-

ture of Mauna Loa is inferred to have been dominated

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 89

by gravitational volcano spreading involving slumping

of shield-stage tholeiitic lavas along faults of the

Kao‘iki–Honu‘apo system, associated with sustained

seaward displacements. Such a structural geometry

would have been much like that of the present-day

Kılauea edifice. South-flank spreading and slump fault-

ing along the Kao‘iki–Honu‘apo system are inferred to

have gradually declined on Mauna Loa, as ancestral

Kılauea grew and entered its tholeiitic shield stage

(probably starting ~75–100 ka).

Large-scale landslide failure of the subaerial Mauna

Loa flank deposited widespread breccias on the adja-

cent submarine slopes; these include the Punalu‘u

slump as presently mapped, as well as the breccias of

Loa-type composition that constitute Papa‘u Seamount

and the deep southwestern part of the Hilina bench.

Although now draped by debris-flow and turbidite

deposits from ancestral Kılauea, rocks of both Papa‘u

Seamount and the deeper interior Hilina bench may

have originated as a northeastward continuation of the

Punalu‘u slump, or as smaller debris flows shed from

the Punalu‘u slump and its headwall scarp.

Long before inception of Kılauea, Mauna Loa must

have already grown into a large subaerial volcano.

Based on evidence from lava-accumulation rates and

paleo-shorelines, Mauna Loa is known to have attained

nearly its present size and elevation above sea level by

about 100 ka (Lipman, 1995; Lipman and Moore,

1996). Results from submersible studies now show

that Mauna Loa had developed a large subaerial edifice

even before initial growth of Kılauea (275–300 ka) and

perhaps before 400 ka (Punalu‘u slump). Breccias of

the Punaludu slump, within Papa‘u Seamount, and deep

along the southwest corner of the Hilina bench were all

derived from subaerial Mauna Loa lavas, and the brec-

cias at the latter two localities underlie debris from

ancestral alkalic Kılauea along a low-relief contact

(Fig. 7). Existence of a large pre-Kılauea Mauna Loa

shield and the gently dipping offshore contact between

the two edifices (Fig. 7) are inconsistent with recent

interpretations of a relatively short interval (0.2–0.3

m.y.) between growth of these adjacent volcanoes and

a near-vertical interfingering contact between their lava

accumulations (DePaolo and Stolper, 1996; Baker et al.,

2003).

5.1.2. Mauna Loa ancestry of the transverse boundary

scarp

The transverse scarp that bounds the southwest side

of the Hilina bench (Fig. 2) is interpreted to have

initiated either as a tear fault during emplacement of

the Punalu‘u slump or during subsequent activity on the

south flank of Mauna Loa, based on the ~15 km

southeast-stepping offset in Mauna Loa breccia depos-

its at water depths of 3000–4000 m. The lip of the

submarine Hilina mid-slope bench has a linear trend

(0408) all the way to its intersection with the transverse

scarp. This trend is oblique by about 208 to the shore-

line of the island, to its submerged continuation west of

Ka’ena Point, and to the long lower east rift zone of

Kılauea (below Napau Crater, ~800 m elevation). The

oblique linear geometry suggests that the trend of the

mid-slope bench may have been imposed by spreading

of Mauna Loa’s south flank before and early in the

history of Kılauea, rather than due primarily to growth

of the tholeiitic Kılauea shield and to slump processes

along Hilina faults.

The transverse scarp has no structural expression on

land, despite thorough mapping of ground cracks and

other structures along the southwest rift zone of Kılauea

(Holcomb, 1980; Wolfe and Morris, 1996; D. Swanson

and R Fiske, written commun., 2002). On gravity and

aeromagnetic maps, the topographic and geologic axes

of the southwest rift zone can be followed without

detectable offset across the projected intersection with

the submarine transverse boundary structure, suggest-

ing that most displacement along the transverse bound-

ary preceded major growth of this rift zone. Amplitudes

of both geophysical anomalies along the southwest rift

zone decrease near the projected intersection, however,

and presence of the transverse structure in Mauna Loa

rocks may have impeded propagation of this Kılauea

rift farther to the southwest. Furthermore, the slope

exposing in-place weakly alkalic Kılauea pillow lavas

is continuous in trend and aspect with the flank of the

tholeiitic Puna Ridge, suggesting that major displace-

ments along the transverse boundary preceded eruption

of the weakly alkalic basalts. Accordingly, the trans-

verse boundary seems unlikely to have developed

chiefly during the late tholeiitic shield stage of Kılauea

(since ~40 ka), as proposed by Morgan et al. (2003).

In contrast to the absence of subaerial structural

expression of the transverse scarp adjacent to the sub-

aerial Hilina faults, the similar-trending Wai‘ohinu fault

that bounds southwest margins of the Kaodiki–Hon-

u‘apo fault system on subaerial Mauna Loa is defined

by a lava-draped scarp and open fractures. This struc-

ture is traceable offshore as a bathymetric scarp that

bounds the Punalu‘u slump to N�3500 m depth. The

Wai‘ohinu fault accommodated at least 2 m of lateral

offset during the 1868 south flank M =8.1 earthquake

(Hitchcock, 1909, p. 105–106; Wood, 1914) and is

historically the more active of the two transverse struc-

tures, at least above sea level.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10890

5.1.3. Deformation of Mauna Loa during growth of

Kılauea

At the present time, in additional to episodic magma-

generated deformation at Kılauea’s summit and along

rift zones, the entire south flank of Hawai‘i Island is

spreading in a seaward direction (Fig. 5). No major

velocity discontinuities are evident across the surface

contact between lavas from Mauna Loa and Kılauea,

and except for times of inflation–deflation at Kılauea’s

summit or dike-injection events along rift zones, the

horizontal displacements increase continuously toward

the coastline. Based largely on south-flank fault geom-

etries, we infer that similar motions have been typical in

the past, with the Mauna Loa flank having hosted larger

displacements in earlier times when Kılauea was a

smaller volcano. Such an interpretation is supported

by the broad pattern of deep seismicity across the entire

south flank (Fig. 6-C), down to the base of the com-

posite constructional volcanic accumulation, without

expression of the depositional or structural boundaries

between the two volcanoes.

If this structural and geochronologic reconstruction

for Mauna Loa at the birth of Kılauea is valid, simple

calculations can place rough limits on the geometry

and long-term motion of Mauna Loa’s south flank

(Table 3). If the flank of Mauna Loa had formerly

been spreading southward at rates comparable to pres-

ent-day Kılauea (~8 cm/yr at sea level, including

sustained deformation plus effects of 1868 and

1975-type earthquakes), and gradually slowed to

20% or less of such a rate as Kılauea grew, then its

coastline would have been displaced ~18 km seaward

since the birth of this volcano at ~300 ka. Coastal

displacement of paleo-Mauna Loa would have been

~6–7 km since inception of shield-stage Kılauea at

150 ka (initial eruption of transitional basalt). Even if

Mauna Loa had been spreading more slowly at 300 ka

(5 cm/yr), perhaps because this volcano was already

near present size and growing only modestly, its

southward motion since birth of Kılauea would still

have been ~11 km, and about 4 km since inception of

its shield-stage volcanism (Table 3).

Vertical components of deformation are not consid-

ered here, because these are subordinate in scale to

long-term horizontal motions on the south flank, seem

more strongly influenced by short-term magma dy-

namics, and are less precisely constrained by GPS

measurements.

5.2. Growth history of Kılauea

The new geochemical and geochronologic results

from submersible dives along the Hilina lower scarp

provide a record of the initial growth of Kılauea,

starting at ~275–300 ka with eruptions of composi-

tionally diverse highly alkalic lavas, followed by

weakly alkalic basalt (~200–150 ka), then transitional

basalt (~150–100 ka), and finally modern-type tholei-

ite (100 ka-present).

No in-place lava exposures of compositionally di-

verse early alkalic lavas were encountered during dives;

the observed record for this stage consists entirely of

the stratified volcaniclastic rocks containing abundant

breccia clasts along the lower scarp beneath the mid-

slope bench. Despite the absence of direct samples from

the early edifice, the broad range of alkalic clast com-

positions (Sisson et al., 2002) provides a record of

perhaps even earlier preshield-stage growth at Kılauea

than that well documented for Lo‘ihi Seamount.

In contrast, sequences of in-place pillow basalts

above and east of the mid-slope bench define the later

submarine growth history of Kılauea. The 800-m high

outcropping rib of alkalic pillow basalt (dives K208,

S709) is compositionally similar to the least alkalic

clasts sampled from breccias below the mid-slope

bench (Fig. 3; Coombs et al., 2006-this issue; Kimura

et al., 2006-this issue) and, accordingly, is interpreted to

represent a late stage of ancestral alkalic volcanism.

Such interpretations based on stratigraphy and petrolo-

gy are in accord with the relatively young Ar–Ar ages

obtained from the pillowed rib (~160F20 ka; 5 sam-

ples), in contrast to dates as early as 270 ka from more

compositionally diverse alkalic clasts in breccias below

the bench (Calvert and Lanphere, 2006-this issue). The

Table 3

Inferred spreading history (coastal), Mauna Loa and Kılauea, since birth of Kılauea at ~300 ka

Current rate,

south coast

Volcano 300 ka

(cm/yr)

Total km

300–150 ka

150 ka*

(cm/yr)

Total km

150–100 ka

100 ka

(cm/yr)

Total km

100–0 ka

Present

(cm/yr)

Cumulative

total (km)

Mauna Loa 8 12 8 3.25 5 3.25 1.5 18.5

8 cm/yr Kilauea 0 0 0 0.75 3 4.75 6.5 5.5

Mauna Loa 5 7.5 5 2 3 2 1 11.5

5 cm/yr Kilauea 0 0 0 0.5 2 3 4 3.5

*Infers shield-stage Kılauea and its spreading commenced with dominant eruption of transitional basalts at ~150 ka.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 91

alkalic pillow lavas seem likely to continue into at least

somewhat shallower water, above the highest outcrops

found during dive S709 (�1820 m).

Transitional basalts, like those exposed along the

east side of the mid-slope bench down slope from the

proximal east rift zone (K95, S504), are likely present

beneath subaerially exposed tholeiite and above the

sampled rib of alkalic pillows offshore from Kılauea’s

summit area. If similarly thick, ~800 m of transitional

basalt should be present on the upper submarine slope,

shallower than �1800 m, beneath a slope mantle of

glass sand and other detritus from the shoreline. Pres-

ence of transitional basalt flows low along subaerial

Hilina fault scarps (see Section 5.2.3) hints that the

cumulative thickness of this compositional type may

be even greater. These extrapolations suggest that the

section of modern-type Kılauea tholeiite that accumu-

lated underwater down slope from the summit is b1000

m thick and erupted largely since 100 ka.

Such a relatively thin carapace of tholeiitic lava is

consistent with the absence of tholeiitic clasts in the

breccias on the lower scarp of the Hilina bench, and the

rarity of such compositions as pillow lavas until reach-

ing the submarine Puna Ridge continuation of Kılauea’s

east rift zone. The single sample of slope-mantling

tholeiitic lava, on the flat eastern end of the Hilina

mid-slope bench (top of dive S504-R5), appears to be

a subaerially erupted shoreline-crossing flow (Lipman

et al., 2002), but accumulation of lava of this compo-

sition must have been largely confined to relatively

shallow parts of the upper slope below the present-

day summit of Kılauea. Eastward along the submarine

slopes of Kılauea’s east rift zone, basalts of transitional

and modern-type tholeiite accumulated at greater

depths (dive S506), and lavas along the crest of the

Puna Ridge are uniformly modern-type tholeiites (Cla-

gue et al., 1995; Johnson et al., 2002). Growth of

tholeiitic shield-stage Kılauea has been primarily

through construction of the east rift zone; vertical lava

accumulation at the summit region has been subordi-

nate, due to proximity of the Mauna Loa flank.

No large landslide slope failures appear to have

incised the tholeiitic shield of Kılauea, as demonstrated

by the absence of clasts of appropriate composition in

the thick breccia sequences of the Hilina bench, and by

the absence of a debris field of modern-type Kılauea

tholeiite in deep water beyond the bench. Relatively

recent volcaniclastic sedimentation from tholeiitic

Kılauea has been trapped as poorly consolidated turbi-

dite sands and minor landslide breccias deposited with-

in the closed basin behind the lip of the bench, and as

near surface fine-grained sands transported to greater

water depths (Naka et al., 2002). The limited extent of

such material is exemplified by the single clast of Kea-

type tholeiite (degassed, subaerially erupted) among the

suite of 16 breccia clasts recovered by dive K207 from

the compositional diverse supra-bench volcaniclastic

sequence that appears to lap around Papa‘u Seamount

(Coombs et al., 2006-this issue). The estimated small

volume of the mid-slope basin fill (~15–25 km3, based

on 1.5 km maximum thickness: Hills et al., 2002) is

also consistent with presence of only a relatively thin

veneer of Kılauea tholeiite, overlying the composition-

ally diverse alkalic and transitional lavas and debris

down slope from the summit. Accordingly, debris-

flow breccia and turbidite sandstone of the lower

scarp likely represent repeated small-scale slope fail-

ures during submarine growth of the alkalic and tran-

sitional basalt stages at ancestral Kılauea, prior to

development of a tholeiitic shield.

A remaining issue is the source of low-S glass sand

grains with compositions unlike the greatly predomi-

nant Loa-type tholeiites in turbidite sandstones and

breccia matrix along the Hilina lower scarp. Of ~1000

glass grains analyzed from lower scarp sandstones

(Coombs et al., 2004c), 80% have Sb400 ppm and

plausibly were erupted subaerially or in very shallow

water (Sisson et al., 2002; Coombs et al., 2006-this

issue). Eighty-eight percent of these low-S grains lie

on the tholeiitic side of the Macdonald–Katsura divid-

ing line, of which 80% plot in the region of common

Mauna Loa magmas (based on SiO2–TiO2 and SiO2–

total alkali variations), 5% plot in the field of modern-

type Kılauea tholeiites (exclusive of the region com-

monly overlapped by Mauna Loa compositions), and

15% are transitional, plotting at higher TiO2 and total-

alkali contents than most modern-type Kılauea tho-

leiites at equivalent SiO2. Compositions of the transi-

tional grains are continuous with low- and high-S

alkalic grains across the Macdonald–Katsura line, and

are otherwise indistinguishable in composition from

higher-S transitional glasses. A straightforward inter-

pretation of these results (Sisson et al., 2002; Coombs

et al., 2006-this issue) is that the great majority of low-S

grains originated from subaerial Mauna Loa tholeiitic

lavas that fragmented upon entering the sea, that the

low-S transitional and alkalic magmas were erupted

from a portion of early Kılauea that approached or

exceeded sea level, and that the rare Kea-type grains

were derived from Kılauea-like magmas erupted from

Mauna Loa, much as Kılauea now infrequently erupts

Mauna Loa-like magmas (Rhodes et al., 1989). Alter-

natively, some or all of the low-S transitional and

alkalic grains may have originated from Mauna Kea,

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10892

which entered its post-shield transition to alkalic mag-

matism at about 240 ka (Sharp et al., 1996).

5.2.1. Ancestral vent and rift-zone geometry

Recent dive observations and petrologic results also

enable more robust interpretations of the vent geome-

try of early Kılauea. Previous studies emphasized

alkalic clasts and grains with high S in glasses, be-

cause those magmas must have been erupted under

submarine conditions and therefore were unlikely to

have been transported from distant sources. Low-S

alkalic and transitional glass grains were documented

and attributed to portions of the early Kılauea edifice

that approached or breached sea level (Sisson et al.,

2002, p. 198; Lipman et al., 2002, p. 173), but these

interpretations were tentative and the bulk of early

Kılauea was thought to have grown in deep water. A

broad range of eruption depths, from deep water to near

or above sea level is indicated by diverse volatile con-

tents (S, CO2, H2O) of compositionally diverse alkalic

glass fragments and pillow rinds, supporting a view that

early Kılauea vents spanned much of submarine south

flank of Mauna Loa and were not predominantly in deep

water (Coombs et al., 2006-this issue). Such eruptive

activity may have preceded development of a central

vent above a well-defined deep conduit that charac-

terizes the shield stage of Hawaiian volcanoes. The

distribution of early alkalic vents at Kılauea perhaps

was similar to that of post-shield alkalic activity on

volcanoes such as Mauna Kea and Kohala: widely

scattered without strong concentrations at the summit

or along rift zones.

Timing of inception of a central vent at the summit of

Kılauea and development of rift zones at Kılauea remain

poorly known. The 800-m-high pillow rib of alkalic

basalt directly down slope from the present-day Kılauea

summit seems likely to be an exposure of the edifice’s

upper submarine slope, based on continuity of pillowed

outcrops with similar magma compositions, and lack of

significant clastic sections or internal deformation.

These pillows record sustained eruptions of lava that

degassed underwater. Progressive up-section decrease

in volatile-saturation pressures suggests eruption of the

pillows over an appreciable time interval from a central

vent that had become established by ~150 ka (Calvert

and Lanphere, 2006-this issue). Eruption depths may

have been shallower than the several kilometers com-

puted from gas-saturation equilibria, however, because

of possible resorption of volatiles (mainly CO2) during

down-slope flow (Coombs et al., 2006-this issue). The

thick sections of transitional basalt down slope from the

subaerial east rift zone (dives K95, S504) seem plausibly

erupted from an early stage of that rift; their volatile

contents suggest degassing equilibria in water depths

only slightly shallower than present locations (�2900–

3700 m). Such approximations suggest that the earliest

alkalic volcanism was from widely scattered vents, but

Kılauea’s central vent and rift zones had developed part

way down the submarine south slope of the island by the

time of late alkalic and succeeding transitional volcanism

(200–100 ka?), similar to present-day Lo‘ihi Seamount.

5.2.2. Structure and deformation

Interpretations of the overall structure and deforma-

tion kinematics of the south flank have been controver-

sial, with alternatives (not entirely mutually exclusive)

that include: (1) large-scale landsliding (Moore and

Krivoy, 1964); (2) low-angle deformation at mid-depths

within the volcanic edifice, accompanied by shallow

slumping, and associated with intrusion of dikes along

Kılauea’s rift zones (Swanson et al., 1976; Hill and

Zucca, 1987; Riley et al., 1999; Cervelli et al., 2002a,

b); (3) deeply rooted slumping controlled by a master

detachment fault at the base of the volcanic edifice,

with distal compression and uplift at the toe of the

slump (Lipman et al., 1985, 2002, 2003; Denlinger

and Okubo, 1995; Ma et al., 1999); (4) deep gravita-

tionally driven volcano spreading, amplified by pres-

ence of dense low-viscosity olivine cumulates in deep

portions of the magmatic system (Macdonald, 1965;

Thurber and Gripp, 1988; Clague and Denlinger,

1994; Delaney et al., 1998; Smith et al., 1999); and

(5) deep deformation along long traveled imbricate

thrust faults that repetitively stack portions of the flank-

ing volcaniclastic apron in a geometric configuration

analogous to the structure of island-arc accretionary

prisms (Morgan et al., 2000, 2003; Hills et al., 2002).

Common to all recent interpretations, however, are

major roles for gravitational volcano spreading, recog-

nition of the Hilina fault system as a proximal subaerial

component of south-flank structures that continue un-

derwater to the distal flank of the volcanic edifice, and a

role for lateral motion along a master detachment be-

tween the base of the edifice and underlying oceanic

crust. For the discussion and conclusions in this paper,

resolution of the alternative interpretations of cumula-

tive lateral motion and relative roles of basal decolle-

ment versus intra-edifice deformation is less important

than the consistent recognition of large lateral motions

on the south flank.

5.2.3. Lava-accumulation rates

The submarine compositional stratigraphy, in con-

junction with age determinations, provides a basis for

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 93

estimating lava- and sediment-accumulation rates dur-

ing Kılauea’s growth (Table 4). Such estimates are

weakly constrained for the early alkalic rocks, sam-

pled only as breccia clasts and alkalic glass grains in

sandstones from the lower scarp. The shape of the

ancestral Kılauea edifice, overlying the flank of

Mauna Loa is poorly understood, and the volcaniclas-

tic rocks have been compressed and uplifted, either by

simple shortening of modest extent (Lipman et al.,

2000) or, alternatively, by long-traveled imbricate

thrust faults (Morgan et al., 2000). Volcaniclastic

rocks in the 2-km-high lower scarp appear to have

accumulated during the interval 275 to b150 ka (pos-

sibly 300 to 100 ka), based on the dated clasts of

these ages (limiting values, based on the absence of

modern-type Kılauea tholeiites as clasts and the like-

lihood that the oldest alkalic material has not been

sampled). Such ranges yield average sedimentation

rates of 10–15 mm/yr for the volcaniclastic sec-

tion—seemingly plausible (even if not appreciably

thickened by deformation) for accumulation on the

steep seaward flank of a rapidly-growing elongate

edifice. Because the majority of grains in lower-

scarp sandstones are from subaerial Mauna Loa, and

sandstone is a significant fraction of exposures, sedi-

mentation rates from early alkalic Kılauea were likely

in the range 5–10 mm/yr.

Lava-accumulation rates during the late alkalic stage

are better defined, from relations above the mid-slope

bench. Alkalic basalts on the pillow rib east of Papa‘u,

sampled from �2570 to 1820 m (dives K208, S709),

were emplaced near present water depths (Coombs et

al., 2006-this issue). Four dated samples from the lower

half of this sequence (dive K208) have similar ages,

averaging ~160 ka (Calvert and Lanphere, 2006-this

issue); compositionally similar alkalic basalt pillows

higher on the rib (S709) must be younger. These out-

crops, with a combined stratigraphic thickness of ~800

m, probably represent an area of rapid lava accumula-

tion directly down slope from the present-day summit of

Kılauea. If they represent the interval 200–150 ka, as

seems reasonable, then the accumulation rate would

have been ~15 mm/yr.

Transitional-composition basalts at the east end of

the mid-slope bench are exposed from �3730 to

�3530 m (S504) and �3280 to �2870 m (K95),

suggesting a composite thickness of 860 m or more

(possibly complicated by structural disruption between

the two dive sites?). These exposures, although down

slope from the east rift zone rather than the summit

area, may also have accumulated rapidly, because the

Kılauea edifice should have thickened in this direction

away from the south flank of Mauna Loa. If these lavas

were erupted mainly 150–100 ka (as estimated in Table

4), the lava-accumulation rate would have been 16 mm/

yr. A similar accumulation rate (16.4 mm/yr) has been

interpreted for tholeiite flows in the SOH1 drill core

(directly upslope from the S504 site), based on mag-

netic paleointensity variations that indicate eruption of

the entire subaerial section (740 m) since 45 ka (Teanby

et al., 2002). Extrapolation to the bottom of this hole

(1685 m), which projects in cross-section to nearly the

same stratigraphic level as the shallowest transitional

basalts sampled by dive S504 (Lipman et al., 2002, Pl.

1A), suggests an age of ~100 ka for inception of

tholeiite eruptions, as well as nearly uniform long-

term accumulation rates for transitional and tholeiitic

flows from the middle east rift.

Although dive S709 to the top of the pillowed rib of

alkalic basalt failed to locate any major compositional

boundary, transitional basalt almost certainly accumu-

lated above the alkalic pillows and below the present-

day tholeiitic lavas that are present all along the shore-

line of Kılauea. For transitional and tholeiitic lava to

have accumulated from the highest sampled outcrop of

alkalic pillows at �1820 m to present sea level since

150 ka requires an average accumulation rate of 12

mm/yr). If the transitional lavas above the pillow rib

are approximately similar in thickness to the composite

section of dives K95-S504 (850 m), then about half the

section above the pillowed rib would be transitional

basalt, and half tholeiite. If the age of the uppermost

alkalic pillows (perhaps even shallower than the highest

sample at �1820 m) is ~150 ka, and accumulation rates

were relatively constant during eruption of the overly-

ing transitional and tholeiitic lava, then dominant erup-

Table 4

Estimated lava-accumulation rates, submarine south flank of Kılauea

Composition Age (ka) Time interval (yr�103) Water depth (m) Thickness (m) Accumulation rate (mm/yr)

Modern tholeiite 100–0 100 0 to ~1000? ~1000 ~10

Transitional basalt 150–100 50 b1800 to ~1000? ~800 ~16

Late alkalic basalt 200–150 50 N2570 to b1820 N750 ~15

Alkalic+ trans. 275–100 175 3100 to 5000 ~2000 ~10

Volcaniclastic rocks (Deformed detritus)

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10894

tion of transitional compositions would have changed

to present-day tholeiite at ~75 ka. Alternatively, if the

upper 1000 m of the offshore south-flank section is

tholeiite erupted since 100 ka, its lava-accumulation

rate would have been ~10 mm/yr. Thus, the overall

preshield alkalic phase of Kılauea’s growth (275–150

ka?) was more prolonged than either of the subsequent

transitional and tholeiitic stages, but lava-accumulation

rates may have remained nearly constant (F20%), as

increasing magma supply roughly kept pace with the

growth in surface area of the edifice.

The transitions between compositional groups are

poorly defined from available data at Kılauea or other

volcanoes but likely to be prolonged and complex in

detail. Perhaps the best example of a prolonged transi-

tion is provided by a few young lava flows of transi-

tional basalt (Table 5) and the volumetrically minor but

widespread AD 600–1000 Kulanadokua‘iki tephra

(Fiske et al., 1999; analyses in Dzurisin et al., 1995)

that overlie tholeiitic lavas on subaerial Kılauea. These

subaerial transitional flows and tephra, erupted about

1000 yr ago, are indistinguishable in composition from

the pillow lavas at the east end of the mid-slope bench

in water depths as great as �3700 m, with an estimated

age of 150–100 ka. The subaerial flows are texturally

distinctive in comparison to the pillow lavas, however,

containing abundant plagioclase microphenocrysts;

such groundmass crystallization was probably retarded

by retained volatiles at submarine confining pressures

in the compositionally similar underwater flows. De-

spite some uncertainties due to subaerial weathering

(especially affecting K2O), subaerial Kılauea flows

with transitional compositions appear to become in-

creasingly common low along Hilina fault scarps

(e.g., Chen et al., 1996, Table 1EK6B-77, EK-9-77),

below the Pokaka‘a Ash dated at 39 ka or older

(Easton, 1987; Beeson et al., 1996). Comparisons

based on abundances of incompatible trace elements

(Nb, Zr, Y, Ce) suggest to us that nearly half the flows

(7 of 15) analyzed by Chen et al. from below the

Pokaka’a Ash along the Pu‘u Kapukapu scarp have

compositional affinities to the transitional pillow basalts

sampled east of the Hilina mid-slope bench. A substan-

tial section of interlayered transitional and tholeiitic

basalts may thus be present near sea level along

Kılauea’s south flank.

Other examples of complex transitions include the

pillow rib above the mid-slope bench, where thin vol-

caniclastic sandstones containing abundant basanite

glass grains are locally interbedded with the weakly

alkalic basalt (Coombs et al., 2006-this issue). High on

Lo‘ihi Seamount, pre-shield alkalic and transitional

basalt interfinger complexly (Garcia et al., 1995a).

Complex interfingering of subtly differing tholeiitic

lavas in the early shield-stage of submarine Mauna

Kea has been documented by the Hawai‘i Scientific

Drilling Project (Rhodes and Vollinger, 2004). Alterna-

tions between tholeiitic and alkalic compositions have

also been documented during the transition to post-

shield volcanism at Molokai (Beeson, 1976) and

Table 5

Major-oxide and trace-element analyses of subaerial transitional basalt, Kılauea

Lava flow, Puka Keana Bihopa. Sample sites; Two tumuli north of Hilina Pali road, at 2600’ elevation.

Sample. no. Whole-rock XRF analyses by D. Siems, USGS, Denver

SiO2 TiO2 Al2O3 FeTO3 MgO MnO CaO Na2O K2O P2O5 LOI Total

(%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%)

01L-01 49.1 2.91 13.8 12.3 7.61 0.16 11.0 2.36 0.64 0.33 b0.01 100.21

01L-02 49.2 3.03 13.8 12.5 7.27 0.17 11.0 2.40 0.66 0.33 b0.01 100.36

Sample no. Ba Ce Cr Cu Ga La Nb Nd Ni Rb Sr V Y Zn Zr

(ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)

01L-01 162 38 426 125 21 15 23 26 172 14 435 323 28 112 178

01L-02 166 41 329 127 23 15 22 21 145 13 446 311 27 115 183

Uwekahuna–Kulanadokua‘iki tephra (Dzurisin et al., 1995, Table 4; Fiske et al., 1999)

Sample no. Electon microprobe analyses of glass shards

SiO2 TiO2 Al2O3 FeTO3 MgO MnO CaO Na2O K2O P2O5 LOI Total

L-85-45A 48.6 3.20 13.8 12.8 6.63 0.17 11.2 2.45 0.71 0.39 99.95

L-83-16A 49.4 3.16 13.7 12.8 6.82 0.17 11.5 2.53 0.72 0.35 101.15

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 95

Mauna Kea (Rhodes, 1996). Although it is unknown

whether such prolonged interfingering is typical for the

inception of shield-stage volcanism, uncertainties about

details of the transition should not materially affect the

rough estimates of lava accumulation developed here.

The entire submarine section appears to have accu-

mulated at roughly the same rates, within uncertainties

of the age and thickness approximations. Because the

area of lava coverage would have increased as the

edifice grew, such constant accumulation rates require

substantial increases in volumetric magma discharge

with time. In comparison, the minimum accumulation

rate for shoreline-crossing lavas from Kılauea during the

past 750 yr is N6.4 mm/yr (Lipman, 1995), based on

geologic mapping of subaerial flows (Holcomb, 1980).

This rate is a minimum, perhaps by a factor of two or

more, because it involves the limiting assumption (de-

veloped mainly for evaluation of much lower accumu-

lation rates on Mauna Loa) that no more than a single

flow, with an assumed average thickness of 6 m, crosses

any segment of the shoreline during the time interval

involved. In contrast, the geologic record is clear that

multiple eruptions have spread lava across some seg-

ments of Kılauea shoreline repeatedly during the past

few hundred years, as is particularly well documented

for the Mauna Ulu and Pu‘u ‘O‘o eruptions.

5.2.4. Eruptive volume

Most prior estimates for volume of the Kılauea

edifice, in the range 19–38�103 km3 (Bargar and

Jackson, 1974; DePaolo and Stolper, 1996; Fiske and

Wright, 1997; Quane et al., 2000; Robinson and Eakins,

2006-this issue), were made without considering the

underlying flank of Mauna Loa. The largest estimated

Fig. 8. Geometric model, on which volume calculations for Kılauea (Table 5) are based (see Appendix for discussion of data sources and

assumptions). A. Modeled volume areas for Kılauea (dashed lines), and inferred contours of Mauna Loa south flank (heavy solid-line contours, with

C.I.=1 km; zero contour represents shoreline), where concealed beneath Kılauea. B. Modeled dimensions of Area #1. Dark plane is simplified

contact between Kılauea edifice and underlying flank of Mauna Loa. C. Simple conical model for estimating volume of Kılauea.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10896

volumes are due to inference of near-vertical interfin-

gering between adjacent volcanoes, a geometry now

clearly incorrect for the bulk of the interface between

Kılauea and Mauna Loa (Fig. 7). A simplified approx-

imation that included a crude approximation of the

Mauna Loa flank yielded a volume of 15�103 km3

(Lipman, 1995). In an attempt to develop an improved

estimate, using the new dive observations, the Kılauea

edifice was modeled as four geometrically simple

volumes (Fig. 8): (1) central edifice; (2) Puna Ridge;

(3) lower southwest rift zone; and (4) deep volcaniclas-

tic apron outboard of the lower scarp (Appendix).

Mauna Loa is presumed to have been a large subaerial

volcano, at least since formation of the Punalu‘u slump

at ~400 ka. Continued eruptions of Mauna Loa since

the birth of Kılauea (~275–300 ka) are inferred to have

maintained its subaerial extent, roughly keeping pace

with island-wide gravitational subsidence; such a rela-

tion is especially clear for Mauna Loa since 100 ka

(Lipman and Moore, 1996). Effects on volume relations

from south-flank deformation involving Kılauea are

inferred to be relatively recent in time, modest in

scale, and accordingly neglected in the modeled

volumes (Table 6). Other data and assumptions used

in the calculations are summarized in the Appendix.

Our new, geologically and geochronologically con-

strained, volume estimate for the Kılauea edifice is

10.7�106 km3, 1 /2 to 1 /3 that of prior published

estimates that did not account for a concealed lower

southeast flank of Mauna Loa. This approximation, in

conjunction with inferred lava-accumulation rates, pro-

vides broad limits on eruptive volumes through time. In

this geometric model, the present-day Kılauea summit

is a relatively small scab or barnacle-like blister on the

lower southeast flank of Mauna Loa. Perhaps half or

more of Kılauea’s shield-stage tholeiites by volume lie

Fig. 8 (continued).

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 97

along the east rift zone and Puna Ridge, and the tho-

leiitic lava exposed so widely on subaerial Kılauea

thinly veneers diverse alkalic and transitional basalts

of ancestral Kılauea that in turn overlie lower-flank

volcaniclastic rocks of Mauna Loa. Such a geometry

also requires that the deep magmatic plumbing system

of Kılauea, both below the summit caldera and along its

rift zones, passes through rocks of Mauna Loa’s shield-

stage south flank that continued to spread seaward as

the Kılauea edifice has grown (Fig. 7).

5.2.5. Changing magma supply

In combination, the estimated lava-accumulation

rates and overall edifice volume permit approximating

the magma supply with time as ancestral Kılauea

progressed from alkalic to tholeiitic stages. With a

total volume for the Kılauea edifice of ~10,000 km3,

the entire Kılauea edifice could have formed within

100,000 yr at the present-day magma-production rate

of ~100�106 m3/yr (Dzurisin et al., 1984; Dvorak and

Dzurisin, 1993). Clearly, magma-production rates have

increased from the early alkalic phase to the present-

day tholeiitic eruptions, as estimated for other Hawai-

ian volcanoes (Wise, 1982; Lipman, 1995; DePaolo

and Stolper, 1996). A model to maintain the approx-

imately constant lava-accumulation rates for the alka-

lic–transitional–tholeiitic sequence observed on the

upper submarine south flank (Table 4), generalized

from a simple conical geometry for the growing

Kılauea shield (Fig. 8C), yields an increase from

25�106 m3/yr at end of alkalic volcanism, to

50�106 m3/yr at end of the transitional basaltic

stage, to 100�106 at the present-day shield stage

(Table 7). From this simple model, about 1250 km3

of alkalic basalt would have erupted at Kılauea (275–

150 ka); 1875 km3 of transitional basalt (150–100 ka);

and 7500 km3 of tholeiite (100 ka–present).

Table 6

Model volume calculations for Kilauea

A. Volume of area #1: central flank and Hilina slope (Fig. 8)

Average NE side (95 km2)+SW side (35 km2)=130 km2 / 2=65 km2

Volume=average side area (65 km2)� length (65 km)=4225 km3

B. Volume of area #2: Puna Ridge:

Length (70 km)�width (35 km)�height (5 km)�1 /4=3062 km2

C. Volume of area #3: lower SW rift zone:

Length (25 km)�width (15 km)�height (1 km)�1 /4=94 km2

D. Volume of area #4: deep volcaniclastic apron:

Length (65 km)�width (15 km)�height (1 km)=975/2=488 km2

Half vol., from Mauna Loa and Mauna Kea :Kilauea

volume=245 km2

E. Volume of average subsidence since 300 ka (area A, only)

Length (65 km)�width (50 km)�height 0.75 Km)=2438 km2

F. Volume of 1-km-high Kao‘iki scarp wedge area

Length (65 km)�avg width (37.5 km)�avg height

(0.25 km)=609 km3

Total Kilauea volume: 10.7�103 km3

(see Appendix for discussion of data sources and assumptions).

In comparison, prior estimates for Kilauea volume:

Bargar and Jackson (1974) 19.4�103 km3.

Lipman (1995) 15�103 km3 [vol. of M.L. estimated].

DePaolo and Stolper (1996) 20–25�103 km3.

Fiske and Wright (1997) 21.1–37.8�103 km3.

Table 7

Estimated lava-supply and growth history of Kilauea

A. Simple conical model for lava volumes (Fig. 8C)

Unit Age

(ka)

Span Accumulation rate Height Radius Cumulative volume Unit volume

(k.y.) (m/yr) (km) (km)

Tholeiitic 100–0 100 0.010 3.25 55 10280 6883

Transitional 150–100 50 0.015 2.25 38 3397 2168

Late alkalic 200–150 50 0.015 1.50 28 1230 1003

Early alkalic 275–200 75 0.010 0.75 17 227 227

B. Estimated lava supply and volume

Composition Age

(ka)

Lava-supply

(�106 m3/yr)

Volume

(km3)

Start End Start rate End rate Average

Modern tholeiite 100 0 50 100 75 7500

Transitional basalt 150 100 25 50 37.5 1875

Late alkalic basalt 200 150 7 25 16 800

Early alkalic basalt 275 200 0 7 3.5 263

Total: 10175

[Excludes endogenous growth by intrusion and cumulates]

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–10898

The conical model (Fig. 8C) is a gross simplifica-

tion, because the shape of Kılauea at any time during its

growth differed in at least two obvious respects: (1) the

summit vent area is asymmetrically upslope from max-

imum lava accumulation on the seaward flank, and (2)

eruptive growth was highly elongate parallel to the

direction of the rift propagation. Nevertheless, the sim-

plified conical model probably provides a plausible

approximation of changes in magma supply with com-

positional evolution. Even though most or all the alkalic

basalt accumulated down slope from the summit, and

much of the tholeiite erupted along the lower east rift

zone and the Puna Ridge, more complex models, in-

volving overlapping elliptical cones, yield roughly sim-

ilar results.

5.3. Implications for geometry of Kılauea’s structure

Growth of Kılauea as a relatively thin blister-like

edifice, riding piggyback on the lower south flank of

Mauna Loa as it continued to spread seaward, helps

account for several previously puzzling aspects of

Kılauea’s structure, especially: (1) location of the sum-

mit magmatic vent so close to the subaerial margin of

the Mauna Loa edifice despite the voluminous subma-

rine eruption of thick pillow lavas during early growth;

(2) contrasting lengths and eruptive activity along

Kılauea’s rift zones; (3) anomalous location of both

Kılauea rift zones; seaward of the summit caldera;

and (4) uniquely arcuate shape of its proximal east

rift zone (Fig. 9).

5.3.1. Location of the summit vent

The present-day proximity to the Mauna Loa flank

of Kılauea’s summit caldera and underlying deep

magmatic plumbing system is a severe geometric

constraint for the submarine eruption of the late alkalic

and transitional basalts, in water as deep as 2–3 km as

indicated by their volatile contents (Coombs et al.,

2006-this issue). The highly variable volatile contents

of early alkalic Kılauea eruptions suggest that a dif-

fuse plumbing system fed widely scattered eruptive

vents for these compositionally diverse basalts. Erup-

tions may have became increasingly focused near the

shallow submarine base of the Kaodiki–Honu‘apo fault

zone and headwall for the Punalu‘u slide, as later

weakly alkalic eruptions increased in volume and a

volcanic edifice became established. A scaled cross-

section through the present-day south flank seemingly

lacks space for such underwater Kılauea eruptions,

however, even if high scarps are assumed along the

fault zone.

Such a geometry for focused submarine eruptions

at ancestral Kılauea is geometrically more feasible if

the Mauna Loa flank and its fault zone were farther

northwest at the time of early Kılauea eruptions at

200–300 ka, providing space for eruptions low on this

flank. Continued seaward spreading of Mauna Loa’s

south flank (Table 3), would subsequently have carried

the Kaodiki–Honu‘apo faults closer to the central con-

duit of Kılauea that remained nearly vertically above

its mantle magma supply, even as the growing Kılauea

edifice was carried seaward along with the entire south

flank of the island. Such spreading would also have

transported the late alkalic pillow basalts away from

the fixed summit conduit and vent, helping account

for the volatile-saturation pressures near present out-

crop depths (Coombs et al., 2006-this issue). The

absence of a Mauna-Loa-side btailQ on the Kılauea

summit gravity anomaly (Kauahikaua et al., 2000)

indicates that the magma conduit has not migrated

southeast along with the edifice, despite tendency for

plate movement to carry the volcano away from the

hot-spot locus, or that the bulk of the gravity anomaly

results from olivine-rich cumulates that became volu-

minous only during the relatively recent (~100 ka)

tholeiitic stage when Kılauea has been fed by picritic

primary magmas (Clague et al., 1995).

Fig. 9. Schematic diagrams of present-day Kılauea structures (A), and

inferred relations at ~200 ka (B), assuming ~10 km of subsequent

south-flank seaward spreading. The summit conduit of Kılauea,

through which magma rises from the mantle, is inferred to have

remained fixed during shield growth (since ~200 ka). Seaward spread-

ing of the mobile south flank of Mauna Loa has carried upper slopes

of this volcano closer to the Kılauea magma conduit, while carrying

the Kılauea rift zones passively southward and generating their arcu-

ate axes. The present-day Ko‘ae fault zone (K.f.z) marks the former

connection between more rectilinear ancestral rift zones.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 99

5.3.2. Contrasts between rift zones

Kılauea’s east rift zone and its submarine continua-

tion along the Puna Ridge is among the longest Hawai-

ian rifts, exceeded only by the east rift of Kılauea (Hana

Ridge). Both rift zones probably have achieved excep-

tional length because their respective edifices were

surrounded only by water to the east, while impeded

by older adjacent volcanoes in other directions.

The southwest rift zone of Kılauea is much more

limited in map dimension, subaerial morphology, and

geophysical expression than the east rift zone. The

southwest rift zone has little expression underwater

and no Kılauea lavas or coarse detritus were encoun-

tered during dive S507 (sited along the down-slope

projection of this rift), in accord with its weak devel-

opment. Development of a Kılauea rift to the southwest

was likely impeded by the increasing size of the Mauna

Loa edifice in this direction, increasing depth and

steepness of the basal decollement that would impede

dilation and dike intrusion (Thurber and Gripp, 1988),

and probable partial blockage along the submarine

transverse boundary of the Hilina bench, in contrast

with deep open water for a rift zone to propagate to the

east. In addition, continued seaward spreading, maxi-

mized down slope from Mauna Loa’s summit, would

minimize dilation on this side of the growing Kılauea

edifice. In contrast, the decreasing component of

Mauna Loa spreading eastward, likely becoming incon-

sequential east of Kılauea’s summit, would produce a

component of counterclockwise rotation along the

south flank and focus tensional opening along the

subaerial east rift zone of Kılauea.

5.3.3. Location and curvature of the rift zones

The pronounced proximal curvature of the east rift

zone, along which the bulk of Kılauea’s flank erup-

tions have taken place, has commonly been ascribed

to asymmetric injection of dikes in response to the

mobility of the south flank (Swanson et al., 1976), a

plausible interpretation for this unusual geometry of

Kılauea. If the Kılauea edifice, in addition to its self-

generated component of seaward motion, is also being

transported piggyback-style on the south flank of

Mauna Loa as this volcano spreads along the basal

decollement, however, an additional possibility

emerges. Unlike the summit vent system that main-

tains long-term connection with the deep mantle

magma conduit as indicated by geophysical data, the

rift zones are relatively shallow structures within the

composite volcanic pile along which magma migrates

laterally to erupt or to solidify as dikes. As the Mauna

Loa flank migrated seaward at average rates of several

cm per year (Table 3), the growing Kılauea rift zones,

including their dense cores (dikes, cumulates) that are

expressed as gravity anomalies, were carried passively

along with the entire flank. The initial Kılauea rift

geometry could thereby have been more linear; the

present-day curvature of the proximal rift zones would

be at least in part due to spreading, while summit

vents remained nearly stationary above the near-verti-

cal deep magma conduit.

The pronounced curvature of the proximal east rift

zone would result both from more intense intrusive and

extrusive activity in this direction, toward an open-

ocean flank rather than being impeded by the Mauna

Loa edifice, and also from modest counter-clockwise

rotation (~68?) of the entire Kılauea edifice during

south-flank spreading, due to the asymmetrical location

of the Mauna Loa summit northwest of Kılauea rather

than directly upslope (Fig. 10). The southwest rift zone,

located most directly down slope from Mauna Loa,

would have been most rotated by such spreading; the

lower east rift zone was least affected because of prox-

imity to the axis of rotation.

If one connects middle and lower parts of the two

present-day rift zones (one-rift model, of Fiske and

Swanson, 1992), the connecting line is along the

Ko‘ae fault system, about 6–7 km south of Kılauea’s

summit (Halemaumau). To the degree that the rift zones

lie entirely within the composite Kılauea–Mauna Loa

edifice and could be transported passively, the estimat-

ed seaward displacements on Mauna Loa (Table 3)

would have been sufficient to transport the rift zones

southward to at least near their present positions, from

an initial geometry aligned with the fixed locus of

Kılauea summit eruptions. The present-day bends in

the upper rift zones would have resulted from mainte-

nance of the magmatic connection with the summit

reservoir, as the middle and lower rift systems were

transported southward, passively riding piggyback on

the seaward-spreading south flank of Mauna Loa. The

Ko‘ae faults, which are presently active with dominant

displacements down toward the caldera and accommo-

date inflation–deflation cycles in the summit area (Duf-

field, 1975), may be structurally controlled by a more

linear ancestral rift geometry.

Such interpretations suggest that eventually connec-

tions between summit magmatic locus and the present

rift zones may become unsustainable, and future rift

activity might be re-established upslope of the presently

active rift loci. This would be the reverse of the pro-

posal for a single bbreak-awayQ rift (Fiske and Swan-

son, 1992) that would eventually capture the summit

reservoir.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108100

5.4. Landslide-slump history of Kılauea

The hypotheses presented above, particularly sug-

gestions that the Hilina bench and transverse boundary

scarp are partly relict features that initiated during

emplacement of the Punalu‘u slump and other south-

flank events on Mauna Loa, raise questions about the

history of landslide and slump events during Kılauea’s

growth. Prior interpretations of gravitational-slump and

volcano-spreading structures on the south flank of

Kılauea have mainly differed on interpretation of fault

depths and amounts of displacement: whether the

Hilina faults are shallow slumps or deep listric faults

that merge with the basal decollement, whether distal

motions involve only modest shortening and uplift or

long-traveled imbricate thrusts, and whether the driving

mechanism is forceful dike injection along rift zones or

more passive gravitational spreading of the edifice.

Most or all published interpretations ascribe these fea-

tures and processes entirely to events within Kılauea,

and infer large motions during growth of this edifice.

In contrast, if Kılauea is a relatively thin blister-like

edifice that during much of its growth has been carried

seaward by continuing spreading on the flank of Mauna

Loa, many of the interpretations summarized above

deserve re-evaluation. Evidence is strong for recurrent

small-scale slumping on the south flank of Kılauea,

both early in its growth as recorded by the voluminous

debris-flow breccias containing submarine-erupted

alkalic clasts exposed along the lower scarp below the

mid-slope bench, and during present-day shield-stage

tholeiitic volcanism as documented by the Hilina faults.

Fig. 10. Present-day and inferred ancestral orientations of Kılauea rift zones, illustrating 68 counter-clockwise rotation (hinged at east end of the

island) that is inferred to have resulted from asymmetric down-slope transport of Kılauea on the south flank of Mauna Loa. Dark double-barbed

arrows schematically indicate seaward spreading on south flank of Mauna Loa; lighter arrows, bpiggybackQ migration of Kılauea rift zones. Filled

triangles indicate locations of long-lived historical east rift eruptions at Mauna Ulu (1969–74) and Kılauea (1983–present), MU and PO,

respectively.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 101

Less convincing is evidence for large-scale slope failure

at any stage during the evolution of Kılauea. Features

indicating the absence of any major failure include: (1)

the primarily depositional nature of Kılauea’s upper

submarine slope, above the mid-slope bench; (2) the

linear continuity of the submarine south flank between

the pillowed ribs on the south flank and the Puna

Ridge; (3) concordance of the subaerial–submarine to-

pographic inflection with present-day sea level along

most of the coastline; (4) absence of any documented

extensive debris field southeast of Kılauea; and (5) on-

land geologic evidence that the Hilina faults are rela-

tively young (b39 ka, date for Pokaka‘a Ash, exposed

low in Hilina scarps: Easton, 1987; Beeson et al.,

1996).

(1) The planar to seaward-concave geometry of

Kılauea’s upper south slope, although enhanced by

subsidence along the Hilina fault system, is interpreted

as primarily a constructional feature. Recurrent subsi-

dence of successive summit calderas, and intrusion-

generated uplift associated with development of the

Ko‘ae fault system on the caldera’s seaward side,

have impeded flowage of summit-erupted lava down

adjacent seaward slopes of Kılauea during much of its

growth. No young shoreline-crossing lava flows were

imaged as reflective areas on the mid-slope bench in

side-scan sonar images or were encountered during

dives down slope from the summit. In contrast, sus-

tained activity along upper segments of the rift zones,

especially the proximal east rift have no comparable

topographic barriers to impede seaward flowage of

lava, resulting in augmented submarine lava accumula-

tion relative to the slope segment below the caldera

area. Comparable summit-rift geometry on Mauna Loa,

at elevations above 2000 m, where unmodified by the

Kaodiki–Honu‘apo faults, has also produced a planar

south slope, in contrast to the more arcuate contours

and domical shape of its north flank.

(2) The submarine south flank of Kılauea, expressed

by resistant ribs protruding through coast-derived sed-

iment, is in nearly linear continuity with constructional

pillow-lava slopes of the Puna Ridge beyond the east

cape of the island. This continuity suggests that the

south flank is largely a primary depositional slope,

only modestly modified by sedimentation and small-

scale slumping. In accord with this interpretation, lon-

gitudinal height /distance ratios to the axis of the east

rift zone from the constructional base of the Kılauea

submarine edifice (base of the upper submarine slope at

the mid-slope bench and base of the Puna Ridge) are

nearly constant, consistent with only modest modifica-

tion by slumping.

(3) Paleo-shorelines of Hawaiian volcanoes, when

submerged by subsidence are well defined by inflec-

tions in slope-between steep (originally submarine) and

gentler (originally subaerial). Adjacent to much of the

eastern Hilina fault zone, the slope inflection coincides

with the present shoreline because coverage by lava

flows has been sufficient to compensate for effects of

slump subsidence. Only west of Ka‘ena Point, down

slope from the summit area where lava is impeded from

reaching the coast as just noted, does the shoreline

slope inflection become submerged; even here, the

submerged shoreline just hinges downward to �700

m maximum depth without deflection in trend (0608),

indicating that little in the way of lateral transport has

accompanied downward displacement along this Hilina

fault segment.

(4) Deposits from large submarine debris ava-

lanches around the Hawaiian Islands were recognized

early as swaths of hummocky terrain extending tens to

over 100 km from the bases of the islands (Moore,

1964; Moore et al., 1989). Such bathymetry is absent

southeast of the Hilina bench (Fig. 1). Instead, two

prominent and as many as ten small conical seamounts

that rise from the smoothly sedimented seafloor at

�5000 m depth, are probably Cretaceous seamounts

(Moore and Chadwick, 1995; Smith et al., 1999). Two

low linear ridges parallel the Hilina lower scarp. Sub-

mersible observations and analyses of glasses from the

larger ridge (dive K93) show that it consists of bed-

ded, glassy volcaniclastics similar to rocks of the

Hilina bench, and the linear ridges are interpreted as

slide blocks shed from the bench’s nearby steep front-

al scarp (Lipman et al., 2002; Sisson et al., 2002). The

proximal volcaniclastic apron at the base of the lower

scarp (Fig. 8) likely consists largely of more-fragmen-

ted small-scale slump and slide debris shed from this

scarp (Smith et al., 1999; Leslie et al., 2002). The

absence of an extensive landslide debris field, lack of

thick turbidite layers with shield-stage Kılauea sand

where sampled by piston core south of Hawai‘i Island

(Naka et al., 2002), and the exposures of probable

Cretaceous basement are further evidence against

major flank collapses of Kılauea.

(5) The entire Hilina fault system as exposed on land

appears to have developed late in the growth of

Kılauea. Topographically expressed offsets along

Hilina faults appear entirely to postdate the deposits

of Pahala Ash (Easton, 1987), a widespread stratigraph-

ic marker on the south flank of Hawai‘i Island that was

deposited after about 39 ka (Beeson et al., 1996). No

evidence is preserved on land or underwater for earlier

movement on the Hilina faults.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108102

Thus, the south flank of Kılauea appears to owe its

present morphology and structure largely to construc-

tional volcanic growth, accompanied by seaward

spreading of the entire south flank of Hawai‘i Island,

small-scale slumping that produced the breccia deposits

exposed along the lower scarp early during volcano

growth (as indicated by the absence of tholeiitic clasts),

and relatively late subsidence along the Hilina faults.

Large-scale slumping or landslide failures are likely

future events for the rapidly deforming south flank of

this actively growing volcano.

Acknowledgments

We thank the Japan Marine Science and Technology

Center (JAMSTEC) for multi-year support of ship-based

research on the flanks of Hawaiian volcanoes, chief

scientists Jiro Naka and Eiichi Takahashi for their lead-

ership and guidance during cruises and subsequent data

analysis, and members of the collaborative Japan–USA

scientific team for sharing observations, samples, and in-

progress interpretations. Asta Miklius generously pro-

vided pre-publication geodetic data from the Hawai‘i

Volcano Observatory (plotted in Fig. 5). The manuscript

benefited from review comments by J.K. Morgan, J.M.

Rhodes, R.I. Tilling, and an anonymous referee. Ongo-

ing multi-year discussions with Morgan, despite some-

what divergent perspectives, have been especially

conducive to improved data analysis and interpretation.

Appendix A. Model calculations for eruptive volume

of Kılauea

To estimate the eruptive volume of Kılauea, making

use of the new dive observations, the edifice was

modeled as consisting of four geometrically simple

volumes (Fig. 8): (1) central edifice, (2) Puna Ridge,

(3) lower southwest rift zone, and (4) deep volcaniclas-

tic apron outboard of the lower scarp (Fig. 8). Results

of the volume calculations are listed in Table 6. Only

eruptive volumes were estimated; Kılauea-related intru-

sions and cumulates within the Mauna Loa flank below

the Kılauea’s edifice were neglected.

A.1. Area #1 (central edifice)

In simplified shape, the bulk of subaerial Kılauea

and its adjacent submarine flank lie within a rectangular

block 65�50 km�5 km high (+1 km elevation to �4

km: Fig. 8B). The south flank of Kılauea is morpho-

logically far more complex than the sloping plane of the

model, but scaled cross-sections suggest positive devia-

tions such as the top of the Hilina fault scarp and lip of

the mid-slope bench would be largely offset by a neg-

ative fit along the mid-slope basin. Computed volume

for this simplified and least-constrained segment of

Kılauea is 4225 km3.

Based on generalized contouring for the lower

slope of Mauna Loa (Fig. 8A), rocks of this volcano

appear to underlie the Kılauea edifice across much of

the rectangular area, thinning from southwest to north-

east. With increasing distance from Mauna Loa, the

cross-sectional area of Kılauea becomes proportionally

larger to the east, down rift from its summit. Even

here, Kılauea could be overprinting and re-using a

buried continuation of the Mauna Loa northeast rift,

a possibility hinted by electrical and magnetic trends

(Flannigan and Long, 1987; Hildenbrand et al., 1993)

that could substantially further reduce the calculated

volume for Kılauea.

Also complicating the resulting volume estimate are

uncertainties concerning the degree of interfingering

with Mauna Loa lavas as Kılauea grew, especially if

high scarps were present along the Kao‘iki–Honu‘apo

fault system. Banking of Kılauea lavas against a tapered

scarp, modeled as 1 km high at the west corner of area

#1 and decreasing to zero at the east corner, lowers the

basal plane of the model and adds 610 km3 of additional

volume (Table 6, F). In addition, about 750 m of con-

current shoreline subsidence would have affected area

#1 during the 300,000 yr since inception of Kılauea, at

the present-day rate of 2.5 mm/yr (Moore, 1970, 1987),

further lowering the basal plane separating rocks of

these two volcanoes. Greater subsidence likely occurred

inland, less along the distal submarine flank of this

block. The calculated subsidence volume is 2440 km3.

This model probably overestimates the Kılauea vol-

ume of area #1 by amounts that are difficult to quantify.

During early alkalic growth of Kılauea (perhaps 300–

200 ka), only part of area #1 was likely occupied by

Kılauea rocks; remaining subsided portions would have

been infilled byMauna Loa lavas. Volcaniclastic rocks at

the southeast margin of area #1, along lower scarp,

contain large proportions of sandstone and breccia-ma-

trix sand (at least 50% by volume in exposed dive sec-

tions) derived from subaerial Mauna Loa and perhaps

Mauna Kea. In addition, the concealed southeast-flank

contours on Mauna Loa likely are convex seaward (Fig.

8A), not planar as in the simplified model for area #1

(Fig. 8B). All three such relations would lead to over-

estimate of the area #1 volume of Kılauea, thereby

offsetting any underestimate associated with a steep

contact between volcanoes along the Kao‘iki–Honu‘apo

faults.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 103

Another complication in reconstructing the shape of

ancestral Kılauea (though probably not the volume

estimates) involves evidence that the initial alkalic

Kılauea lavas at 275–300 ka erupted over a wide

range of elevations, from deep water to near or

above sea level (Coombs et al., 2006-this issue),

consistent with the interpretation that Mauna Loa

already was a large subaerial volcano at that time

and that growth of Kılauea began on its flank. In

contrast, later alkalic and transitional pillow lavas

sampled above the mid-slope bench, which appear

related to presence of a central vent and rift zones,

erupted consistently under water, at depths as much as

several thousand meters. Such geometry requires an

additional process on the south flank to provide room

for an underwater central vent, suggested here to

involve something on the order of 10 km of seaward

spreading of the south flank of Mauna Loa during the

growth of Kılauea.

A.2. Area #2 (Puna Ridge)

The Puna Ridge was treated as a simple tapered

prism 35 km wide, 70 km long, and 5 km high at its

proximal end—the east cape of Hawai‘i Island. No

Mauna Loa rocks are modeled as underlying the

prism, and no sizable gravitational subsidence is in-

ferred for this distal part of the volcano, where most

lava has likely accumulated only since beginning of

transitional- and tholeiitic-stage volcanism at ~150 ka.

Calculated volume is 3060 km3.

A.3. Area #3 (lower SW rift zone)

The lower southwest rift is west of the central

rectangle, beyond the transverse boundary scarp (Fig.

8A). Erupted lavas represent only a thin scab on the

flank of Mauna Loa, and the lower southwest rift

structures must largely cut through the Mauna Loa

flank, rather than lying entirely within the Kılauea

edifice (Fig. 7). This portion of the rift zone is only

weakly expressed as a morphologic feature on land

and underwater, its boundaries are uncertain underwa-

ter, and its volume small. Treating this feature as a

simple tapered prism 15 km wide, 25 km long, and 1

km high at its proximal end, the calculated volume is

95 km3.

A.4. Area #4 (deep volcaniclastic apron)

Outboard of the lower scarp is a deep debris field

and volcaniclastic apron, wedging seaward from about

�4500 to �5500 m water depth (Smith et al., 1999;

Leslie et al., 2002). The volcaniclastic apron is broad-

est down slope from the Punalu‘u slump area, narrow-

ing to the northeast beneath the Hilina lower scarp

(Fig. 2; Moore and Chadwick, 1995, fig. 2), thus

suggesting a major detrital component from Mauna

Loa. If half the wedge of debris down slope from the

Hilina scarp (modeled as 15 km wide�65 km

long�1 km high) was derived from Mauna Loa

(and/or Mauna Kea?) as suggested by dominant com-

ponents from these sources in sandstones and breccia

matrix of the scarp sequence, the resulting Kılauea

volume is 245 km3. Contributions from distal ocean-

floor turbidites are neglected; no thick turbidite layers

sampled south of Hawai‘i Island by piston core have

shield-stage Kılauea sand as a primary component

(Naka et al., 2002).

References

Ando, M., 1979. Low-angle faulting due to forceful injection of

magma. J. Geophys. Res. 84, 7616–7626.

Baker, M.B., Stolper, D.A., Stolper, E.M., Fialko, Y., 2003. Modeling

the growth of Hawaiian volcanoes [abs.]. Eos Trans. AGU 84,

F1469.

Bargar, K.E., Jackson, E.D., 1974. Calculated volumes of individual

shield volcanoes along the Hawaiian–Emperor chain. J. Res. U. S.

Geol. Surv. 2, 545–550.

Beeson, M.H., 1976. Petrology, mineralogy, and geochemistry of the

East Molokai Volcanic Series, Hawai‘i. U.S. Geol. Surv. Prof.

Pap. 961, 53 pp.

Beeson, M.H., Clague, D.A., Lockwood, J.P., 1996. Origin and

depositional environment of clastic deposits in the Hilo drill

hole, Hawai‘i. J. Geophys Res. 101, 11,617–11,630.

Borgia, A., Treves, B., 1992. Volcanic plates override the ocean crust:

structure and dynamics of Hawaiian volcanoes. Spec. Publ. Geol.

Soc. London 60, 277–299.

Borgia, A., Delaney, P.T., Denlinger, R.P., 2000. Spreading volcanoes.

Annu. Rev. Earth Planet. Sci. 28, 539–570.

Brigham, W.T., 1909. The Volcanoes of Kılauea and Mauna Loa. B.P.

Bishop Museum Mem. vol. 2. 222 pp.

Calvert, A., Lanphere, M., 2006. Argon geochronology of Kılauea’s

early submarine history. J. Volcanol. Geotherm. Res. 151, 1–18.

doi:10.1016/j.jvolgeores.2005.07.023 (this issue).

Cannon, E.C., Burgmann, R., 2001. Prehistoric fault offsets of the

Hilina fault system, south flank of Kılauea Volcano, Hawai‘i. J.

Geophys. Res. 106, 4207–4219.

Cervelli, P.F., Seagall, P., Amelung, F., Garbeil, H., Meertens, C.M.,

Owen, S.E., Miklius, A., Lisowski, M., 2002. The 12 September

1999 Upper East Rift Zone dike intrusion at Kılauea Volcano

Hawai‘i. J. Geophys. Res. 107, ECV3-1–ECV3-13.

Cervelli, P.F., Seagall, P., Johnson, K., Lisowski, M., Miklius, A.,

2002. Sudden aseismic fault slip on the south flank of Kılauea

Volcano. Nature 415, 1014–1018.

Chadwick Jr., W.W., Smith, J.R., Moore, J.G., Clague, D.A., Garcia,

M.O., Fox, C.G., 1993. Bathymetry of South Flank of Kılauea

Volcano, Hawai‘i. U.S. Geol. Surv. Misc. Field Studies Map, vol.

MF-2231.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108104

Chen, C.-Y., Frey, F.A., Rhodes, J.M., Easton, R.M., 1996. Tempo-

ral geochemical evolution of Kılauea Volcano: comparison of

Hilina and Puna basalt. Geophys. Monogr. Am. Geophys. Union

95, 161–181.

Clague, D.A., Dalrymple, G.B., 1987. The Hawaiian–Emperor vol-

canic chain. Part I. Geologic evolution. U.S. Geol. Surv. Prof. Pap.

1350, 5–73.

Clague, D.A., Denlinger, R.P., 1994. The role of cumulus dunite in

destabilizing the flanks of Hawaiian volcanoes. Bull. Volcanol.

56, 425–434.

Clague, D.A., Hon, K.A., Anderson, J.L., Chadwick Jr., W.W., Fox,

C.G., 1994. Bathymetry of Puna Ridge, Kılauea Volcano,

Hawai‘i. U.S. Geol. Survey Misc. Field Studies Map, vol.

MF-2237.

Clague, D.A., Moore, J.G., Dixon, J.E., Friesen, W.B., 1995. Petrol-

ogy of submarine lavas from Kılauea’s Puna Ridge, Hawai‘i. J.

Petrol. 36, 299–349.

Coombs, M.L., Sisson, T.W., Kimura, J.I., 2004a. Ultra-high Cl in

submarine Kılauea glasses: evidence for direct assimilation off

brine by magma. Earth Planet. Sci. Lett. 217, 297–313.

Coombs, M.L., Clague, D.A., Moore, G.F., Cousens, B.L., 2004b.

The growth and collapse of Wai‘anae Volcano, Hawai‘i, as

revealed by exploration of its submarine flanks. Geochem. Geo-

phys. Geosyst. doi:10.1029/2004GC000717.

Coombs, M.L., Sisson, T.W., Lipman, P.W., 2004c. Major-Element,

S, and Cl Compositions of Submarine Kılauea Glasses Collected

during 1998–2002 JAMSTEC Hawai‘i Cruises. U.S. Geol. Sur-

vey Open-File Report 2004-1378 http://pubs.usgs.gov/of/2004/

1378/.

Coombs, M.L., Sisson, T.W., Lipman, P.W., 2006. Growth history of

Kılauea inferred from volatile concentrations in submarine-col-

lected basalts. J. Volcanol. Geotherm. Res. 151, 19–49.

doi:10.1016/j.jvolgeores.2005.07.037 (this issue).

Crosson, R.S., Endo, E.T., 1982. Focal mechanism and locations of

earthquakes in the vicinity of the 1975 Kalapana earthquake

aftershock zone 1970–1979. Tectonics 1, 495–542.

Dalrymple, G.B., Moore, J.G., 1968. Argon-40: excess in submarine

pillow basalts from Kılauea Volcano, Hawai‘i. Science 161,

1132–1135.

Dana, J.D., 1849. Geology. United States Exploring Expedition, vol.

10. George P. Putnam, New York. 436 pp.

Decker, R.W., Wright, T.L, Stauffer, P.H., 1987. Volcanism in

Hawai‘i. U. S. Geol. Surv. Prof. Pap. 1350. 1667 pp.

Delaney, P.T., Denlinger, R.P., Lisowski, M., Miklius, A., Okubo,

P.G., Okamura, A.T., Sako, M.K., 1998. Volcano spreading at

Kılauea, 1976–1996. J. Geophys. Res. 103, 18,003–18,024.

DePaolo, D.J., Stolper, E.M., 1996. Models of Hawaiian volcano

growth and plume structure: implications of results from the

Hawai‘i scientific drilling project. J. Geophys. Res. 101,

11,643–11,654.

DePaolo, D.J., Bryce, J.G., Dodson, A., Shuster, D.L, Kennedy, B.M.,

2001. Isotopic evolution of Mauna Loa and the chemical structure

of the Hawaiian plume. Geochem. Geophys. Geosyst. 2

(20000GC000139, 23 pp.).

Denlinger, R.P., Okubo, P., 1995. Structure of the mobile south

flank of Kılauea Volcano, Hawai‘i. J. Geophys. Res. 100,

24,499–24,507.

Dieterich, J.H., 1988. Growth and persistence of Hawaiian volcanic

rift zones. J. Geophys. Res. 93, 4258–4270.

Duffield, W.A., 1975. Structure and origin of the Ko‘ae fault

system, Kılauea Volcano, Hawai‘i. U. S. Geol. Surv. Prof. Pap.

856. 12 pp.

Duffield, W.A., Christiansen, R.L., Koyanagi, R.Y., Swanson, D.A.,

1982. Storage, migration, and eruption of magma at Kılauea

Volcano, Hawai‘i, 1971–1972. J. Volcanol. Geotherm. Res. 13,

273–307.

Dutton, C.E., 1884. The Hawaiian volcanoes. U.S. Geol. Survey 4th

Ann. Rept., pp. 75–219.

Dvorak, J.J., Dzurisin, D., 1993. Variations in magma supply at

Kılauea Volcano. J. Geophys. Res. 98, 22,255–22,268.

Dvorak, J.J., Okamura, A.T., English, T.T., Koyanagi, R.Y., Nakata,

J.S., Sako, M.K., Tanigawa, W.T., Yamashita, K.M., 1986. Me-

chanical response of the south flank of Kılauea Volcano, Hawai‘i,

to intrusive events along the rift systems. Tectonophysics 124,

193–209.

Dzurisin, D., Konanagi, R.Y., English, T.T., 1984. Magma supply and

storage at Kılauea Volcano, Hawai‘i 1956–1983. J. Volcanol.

Geotherm. Res. 21, 177–206.

Dzurisin, D., Lockwood, J.P., Casadevall, T.J., Rubin, M., 1995. The

Uwekahuna ash: product of large prehistoric phreatomagmatic

eruptions at Kılauea Volcano, Hawai‘i. J. Volcanol. Geotherm.

Res. 66, 163–184.

Eakins, B.W., Robinson, J.E., Kanamatsu, T., Naka, J., Smith, J.R.,

Takahashi, E., Clague, D.A., 2003. Hawai‘i Volcanoes Revealed.

U.S. Geol. Survey Geol. Map Invest. Series I-2809.

Eaton, J.P., 1962. Crustal structure and volcanism in Hawai‘i. Geo-

phys. Monogr. Am. Geophys. Union 6, 13–29.

Eaton, J.P., Murata, K.J., 1960. How volcanoes grow. Science 132,

925–938.

Easton, R.M., 1987. Stratigraphy of Kılauea Volcano. U.S. Geol.

Surv. Prof. Pap. 1350, 243–260.

Endo, E.T., 1985. Seismotectonic framework for the southeast flank

of Mauna Loa Volcano, Hawai‘i. PhD thesis, Univ. Washington,

Seattle. 349 pp.

Fiske, R.S., Jackson, E.D., 1972. Orientation and growth of Hawaiian

volcanic rifts: the effect of regional structure and gravitational

stresses. Proc. R. Soc. London 329, 299–326.

Fiske, R.S., Swanson, D.A., 1992. One-rift, two-rift paradox at

Kılauea Volcano, Hawai‘i [abs.]. Eos Trans. AGU 73, 506.

Fiske, R.S., Wright, T.L., 1997. Volume of Kılauea: estimates and

implications [abs.]. Eos Trans. AGU 78, F644–F645.

Fiske, R.S., Rose, T.R., Swanson, D.A., McGeehin, J.C., 1999. The

KulanadokuaTiki tephra: product of newly recognized pyroclastic

eruptions at Kılauea Volcano, Hawai‘i [abs.]. Eos Trans. AGU 80,

F1196–F1197.

Flannigan, V.J., Long, C.L., 1987. Aeromagnetic and near-surface

electrical expression of the Kılauea and Mauna Loa rift systems.

U. S. Geol. Surv. Prof. Pap. 1350, 935–946.

Fornari, D.J., Moore, J.G., Calk, L., 1979. A large submarine sand-

rubble flow on Kılauea Volcano, Hawai‘i. J. Volcanol. Geotherm.

Res. 5, 239–256.

Garcia, M.O., Davis, M.G., 2001. Submarine growth and internal

structure of ocean island volcanoes based on submarine observa-

tions of Mauna Loa Volcano, Hawai‘i. Geology 29, 163–166.

Garcia, M.O., Foss, D.J.P., West, H.B., Mahoney, J.J., 1995a. Geo-

chemical and isotopic evolution of Lo‘ihi Volcano, Hawai‘i. J.

Petrol. 36, 1647–1674.

Garcia, M.O., Hulsebosch, T.P., Rhodes, J.M., 1995b. Olivine-rich

submarine basalts from the southwest rift zone of Mauna Loa

Volcano; implications for magmatic processes and geochemical

evolution. Monogr. Am. Geophys. Union 92, 219–239.

Got, J.-L., Okubo, P., 2003. New insights into Kılauea’s volcano

dynamics brought by large-scale relative relocation of microearth-

quakes. J. Geophys. Res. 108 (2337). doi:10.1029/2002JB00260.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 105

Got, J.-L., Frechet, J., Klein, F.W., 1994. Deep fault plane geometry

inferred from multiplet relative relocation beneath the south flank

of Kılauea. J. Geophys. Res. 99, 15,375–15,386.

Guillou, H., Turpin, L., Garnier, F., Charbit, S., Thomas, D.M.,

1997. Unspiked K–Ar dating of Pleistocene tholeiitic basalts

from the deep core SOH-4, Kılauea, Hawai‘i. Chem. Geol. 140,

81–88.

Hildenbrand, T.G., Rosenbaum, J.G., Kauahikaua, J.P., 1993. Aero-

magnetic study of the Island of Hawai‘i. J. Geophys. Res. 98,

4099–4119.

Hill, D.P., Zucca, J.J., 1987. Geophysical constraints on the structure

of Kılauea and Mauna Loa volcanoes, and some implications for

seismomagmatic processes. U.S. Geol. Surv. Prof. Pap. 1350,

903–917.

Hills, D.J., Morgan, J.K., Moore, G.F., Leslie, S.C., 2002. Structural

variability along the submarine south flank of Kılauea Volcano,

Hawai‘i, from a multi-channel seismic reflection survey. Geophys.

Monogr. Am. Geophys. Union 128, 105–124.

Hitchcock, C.H., 1909. Hawai‘i and its Volcanoes. The Hawaiian

Gazette, Co., Honolulu, 314 pp.

Holcomb, R.T., 1980. Preliminary geologic map of Kılauea Volcano,

Hawai‘i. Open-File Rep. U. S. Geol. Surv., 80–796.

Jackson, E.D., Silver, E.A., Dalrymple, G.R., 1972. Hawaiian–Em-

peror chain and its relation to Cenozoic circum-Pacific tectonics.

Geol. Soc. Am. Bull. 83, 601–618.

Jackson, M.D, Endo, E.T., Delaney, P.T, Arnadottir, T., Rubin, A.M.,

1992. Ground ruptures of the 1974 and 1983 Kaoiki earth-

quakes, Mauna Loa Volcano, Hawai‘i. J. Geophys. Res. 97,

8775–8796.

Jagger, T.A., 1917. Lava flow from Mauna Loa, 1916. Am. J. Sci.

193, 255–288.

Johnson, K.T.M., Reynolds, J.R., Vonderhaar, D., Smith, D.K., Kong,

L.S.L., 2002. Petrological systematics of submarine basalt glasses

from the Puna Ridge, Hawai‘i: implications for rift zone plumbing

and magmatic processes. Geophys. Monogr. Am. Geophys. Union

128, 143–159.

Kauahikaua, J., 1993. Geophysical characteristics of the hydrother-

mal systems of Kılauea Volcano, Hawai‘i. Geothermics 22,

271–300.

Kauahikaua, J., Hildenbrand, T., Webring, M., 2000. Deep magmatic

structures of Hawai‘i volcanoes, imaged by three-dimensional

gravity models. Geology 28, 883–886.

Kimura, J.-I., Sisson, T.W., Nakano, N., Coombs, M.L., Lipman,

P.W., 2006. Isotope geochemistry of early Kılauea magmas from

the submarine Hilina bench: the nature of the Hilina mantle

component. J. Volcanol. Geotherm. Res. 151, 51–72.

doi:10.1016/j.jvolgeores.2005.07.024 (this issue).

Kinoshita, W.T., Krivoy, H.L, Mabey, D.R., MacDonald, R.R., 1963.

Gravity survey of the Island of Hawai‘i. U.S. Geol. Surv. Prof.

Pap. 475-C, C114–C116.

Klein, F.W., 1982. Patterns of historic eruptions of Hawaiian volca-

noes. J. Volcanol. Geotherm. Res. 12, 1–35.

Klein, F.W., Koyanagi, R.Y., Nakata, J.S., Tanigawa, W.R., 1987. The

seismicity of Kılauea’s magma system. U.S. Geol. Surv. Prof. Pap.

1350, 1019–1185.

Leslie, S.C., Moore, G.F., Morgan, J.K., Hills, D.J., 2002. Seismic

stratigraphy of the frontal Hawaiian moat: implications for sedi-

mentary processes at the leading edge of an oceanic hotspot trace.

Mar. Geol. 184, 143–162.

Lipman, P.W., 1980a. Rates of volcanic activity along the south-

west rift zone of Mauna Loa, Hawai‘i. Bull. Volcanol. 43,

703–725.

Lipman, P.W., 1980b. The southwest rift zone of Mauna Loa: impli-

cations for structural evolution of Hawaiian volcanoes. Am. J. Sci.

280-A, 752–776.

Lipman, P.W., 1995. Declining growth of Mauna Loa during the last

100,000 yr: rates of lava accumulation vs. gravitational subsi-

dence. Geophys. Monogr. Am. Geophys. Union 92, 45–80.

Lipman, P.W., Moore, J.G., 1996. Mauna Loa lava accumulation

rates at the Hilo drill site: formation of lava deltas during a

period of declining overall volcanic growth. J. Geophys. Res.

101, 11,631–11,641.

Lipman, P.W., Lockwood, J.P., Okamura, R.T., Swanson, D.A.,

Yamashita, K.M., 1985. Ground deformation associated with the

1975 magnitude-7.2 earthquake and resulting changes in activity

of Kılauea Volcano, Hawai‘i. U. S. Geol. Surv. Prof. Pap. 1276,

45 pp.

Lipman, P.W., Normark, W.R., Moore, J.G., Wilson, J.B., Gutmacher,

C.E., 1988. The giant submarine Alika debris slide, Mauna Loa,

Hawai‘i. J. Geophys. Res. 93, 4279–4299.

Lipman, P.W., Rhodes, J.M., Dalrymple, G.B., 1990. The Ninole

basalt—implications for the structural evolution of Mauna Loa

Volcano, Hawai‘i. Bull. Volcanol. 53, 1–19.

Lipman, P.W., Sisson, T.W., Ui, T., Naka, J., 2000. In search of

ancestral Kılauea Volcano. Geology 28, 1079–1082.

Lipman, P.W., Sisson, T.W., Ui, J., Naka, J., Smith, J.R., 2002.

Ancestral submarine growth of Kılauea Volcano and instability

of its south flank. Geophys. Monogr. Am. Geophys. Union 92,

161–191.

Lipman, P.W., Eakins, B., Yokose, H., 2003. Ups and downs on

spreading flanks of ocean-island volcanoes: evidence from

Mauna Loa and Kılauea. Geology 31, 841–844.

Lockwood, J.P., 1995. Mauna Loa eruptive history—the radiocarbon

record. Geophys. Monogr. Am. Geophys. Union 92, 81–94.

Lockwood, J.P, Lipman, P.W., 1987. Holocene eruptive history of

Mauna Loa Volcano. U.S. Geol. Surv. Prof. Pap. 1350, 509–536.

Lockwood, J.P., Dvorak, J.J., English, T.T., Koyanagi, R.Y., Oka-

mura, A.T., Summer, M.L., Tanigawa, W.R., 1987. Mauna Loa

1974–1984: a decade of intrusive and extrusive activity. U.S.

Geol. Surv. Prof. Pap. 1350, 537–570.

Lonsdale, P., 1989. A geomorphological reconnaissance of the sub-

marine part of the East Rift Zone of Kılauea Volcano, Hawai‘i.

Bull. Volcanol. 51, 123–144.

Ma, K.-F., Kanamori, H., Satake, K., 1999. Mechanism of the 1975

Kalapana, Hawai‘i, earthquake inferred from tsunami data. J.

Geophys. Res. 104, 13,153–13,168.

Macdonald, G.A., 1965. Hawaiian calderas. Pac. Sci. 19, 320–334.

Macdonald, G.A., Abbott, A.T., 1970. Volcanoes in the Sea: the

Geology of Hawai‘i. Univ. Hawai‘i Press, 441 pp.

Macdonald, G.A., Katsura, T., 1964. Chemical composition of Ha-

waiian lavas. J. Petrol. 5, 83–133.

Miklius, A., Cervelli, P., 2003. Interaction between Kılauea and

Mauna Loa. Nature 421, 229.

Miklius, A., Lisowski, M., Delaney, P.T., Denlinger, R.P, Dvorak, J.J.,

Okamura, A.T., Sato, M.K., 1995. Recent inflation and flank

movement of Mauna Loa Volcano. Geophys. Monogr. Am. Geo-

phys. Union 92, 199–206.

Miklius, A., Cervelli, P., Lisowski, M.,Owen, S., Sako, M., Segall, P.,

in press. Global positioning system measurements on the Island of

Hawai‘i: 1997–2003. Open-File Rep. U. S. Geol. Surv., 2005.

Mitchell, N.C., 2001. The transition from circular to stellate forms of

submarine volcanoes. J. Geophys. Res. 106, 1987–2003.

Moore, J.G., 1964. Giant submarine landslides on the Hawaiian

Ridge. U. S. Geol. Surv. Prof. Pap. 501-D, D95–D98.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108106

Moore, J.G., 1970. Relationship between subsidence and volcanic

load, Hawai‘i. Bull. Volcanol. 34, 562–576.

Moore, J.G., 1987. Subsidence of the Hawaiian Ridge. U.S. Geol.

Surv. Prof. Pap. 1350, 85–100.

Moore, J.G., Chadwick Jr., W.W., 1995. Offshore geology of Mauna

Loa and adjacent areas, Hawai‘i. Geophys. Monogr. Am. Geo-

phys. Union 92, 21–44.

Moore, J.G., Clague, D.A., 1992. Volcano growth and evolution of

Hawai‘i Island. Geol. Soc. Am. Bull. 104, 1471–1484.

Moore, J.G., Krivoy, H.L., 1964. The 1962 flank eruption of Kılauea

Volcano and structure of the east rift zone. J. Geophys. Res. 69,

2033–2045.

Moore, J.G., Thomas, D.M., 1988. Subsidence of Puna, Hawai‘i,in-

ferred from sulfur content of drilled lava flows. J. Volcanol.

Geotherm. Res. 35, 165–171.

Moore, J.G., Philips, R.L., Grigg, R.W., Peterson, D.W., Swanson,

D.A., 1973. Flow of lava into the sea, 1969–1971, Kılauea

Volcano, Hawai‘i. Geol. Soc. Am. Bull. 84, 537–546.

Moore, J.G., Clague, D.A., Normark, W.R., 1982. Diverse basalt

types from Kılauea Seamount, Hawai‘i. Geology 10, 88–92.

Moore, J.G., Clague, D.A., Holcomb, R.T., Lipman, P.W., Normark,

W.R., Torresan, M.E., 1989. Prodigious submarine landslides on

the Hawaiian Ridge. J. Geophys. Res. 94, 17465–17484.

Morgan, J.K., 2006. Volcano tectonic interactions between Mauna

Loa and Kılauea: insights from 2-D discrete element simulations.

J. Vol. Geotherm. Res. 151, 109–131 doi:10.1016/j.jvolgeores.

2005.07.025 (this issue).

Morgan, J.K., Clague, D.A., 2003. Volcanic spreading on Mauna Loa

Volcano, Hawai‘i. Evidence from accretion, alteration, and exhu-

mation of volcaniclastic sediments. Geology 30, 411–414.

Morgan, J.K., Moore, G.F., Hills, D.J., Leslie, S., 2000. Overthrusting

and sediment accretion along KVlauea’s mobile south flank,

Hawai‘i: evidence for volcanic spreading from marine seismic

reflection data. Geology 28, 667–670.

Morgan, J.K., Moore, G.F., Clague, D.A., 2003. Papa’u Seamount

and the Hilina slump: slope failure and volcanic spreading along

the mobile south flank of Kılauea Volcano, Hawai‘i. J. Geophys.

Res. 108, EPM1-1-23. doi:10.1029/2003JB002411.

Naka, J., Scientific Team, 2000. Tectono–magmatic processes inves-

tigated at deep water flanks of Hawaiian volcanoes. Eos Trans.

AGU 81, 221–227.

Naka, J., Kanamatsu, T., Lipman, P.L., Sisson, T.W., Tsuboyama, N.,

Morgan, J., Smith, J.R., Ui, T., 2002. Deep-sea volcaniclastic

sedimentation around the southern flank of Hawai‘i Island. Geo-

phys. Monogr. Am. Geophys. Union 128, 29–50.

Okamura, A.T., Dvorak, J.T., Koyanagi, R.Y., Tanigawa, W.R., 1988.

Surface deformation during dike propagation. U.S. Geol. Surv.

Prof. Pap. 1463, 165–182.

Okubo, P., Benz, H.M., Chouet, B.A., 1997. Imaging the crustal

magma sources beneath Mauna Loa and Kılauea volcanoes,

Hawai‘i. Geology 25, 867–870.

Owen, S., Segall, P., Lisowski, M., Miklius, A., Denlinger, R., Sako,

M., 2000. Rapid deformation of Kılauea Volcano: global posi-

tioning system measurements between 1990 and 1996. J. Geo-

phys. Res. 105, 18,983–18,998.

Quane, S.L., Garcia, M.O., Guillou, H.J., Hulsebosch, T.P., 2000.

Magmatic history of the east rift zone of Kılauea Volcano,

Hawai‘i, based on drill core from SOH 1. J. Volcanol. Geotherm.

Res. 94, 233–250.

Rhodes, J.M., 1996. Geochemical stratigraphy of lava flows sampled

by the Hawaiian scientific drilling project. J. Geophys. Res. 101,

11,729–11,746.

Rhodes, J.M., Vollinger, M.J., 2004. Compositions of basaltic lavas

sampled by Phase-2 of the Hawaiian Scientific Drilling Project:

geochemical stratigraphy and magma types. Geochem. Geophys.

Geosyst. 5. doi:10.1029/2002GC000434.

Rhodes, J.M., Wentz, M.K, Neal, C., Sparks, J., Lockwood, J.P.,

1989. Geochemical evidence for invasion of Kılauea’s plumbing

system by Mauna Loa magma. Nature 337, 257–260.

Riley, C.M., Diehl, J.F., Kirschvink, J.L., Ripperdam, R.L., 1999.

Paleomagnetic constraints on fault motion in the Hilina fault

system, south flank of Kılauea Volcano, Hawai‘i. J. Volcanol.

Geotherm. Res. 102, 319–338.

Robinson, J.E., Eakins, B.W., 2006. Calculated volumes of indi-

vidual shield volcanoes at the young end of the Hawaiian

Ridge. J. Volcanol. Geotherm. Res. 151, 309–317. doi:10.1016/

j.jvolgeores.2005.07.033 (this issue).

Rubin, M., Gargulinski, L.K., McGeehin, J.P., 1987. Hawaiian radio-

carbon dates. U.S. Geol. Surv. Prof. Pap. 1350, 213–242.

Ryan, M.P., 1988. The mechanics and three-dimensional internal

structure of active magmatic systems: Kılauea Volcano, Hawai‘i.

J. Geophys. Res. 93, 4213–4248.

Ryan, M.P., Koyanagi, R.Y., Fiske, R.S., 1981. Modeling the

three-dimensional structure of magma transport systems: appli-

cation to Kılauea Volcano, Hawai‘i. J. Geophys. Res. 80,

1295–1308.

Sansone, F.J., Smith, J.R., 2006. Rapid mass wasting following

nearshore submarine volcanism on Kılauea Volcano. J. Volcanol.

Geotherm. Res. 151, 133–139. doi:10.1016/j.jvolgeores.2005.

07.026 (this issue).

Sharp, W.D., Turrin, B.D., Renne, P.R., 1996. The 40Ar / 39Ar and K/

Ar dating of lavas from the Hilo 1-km core hole, Hawai‘i Scien-

tific Drilling Project. J. Geophys. Res. 101, 11,607–11,616.

Sisson, T.W., 2003. Native gold in a Hawaiian alkalic magma. Econ.

Geol. 98, 643–648.

Sisson, T.W., Lipman, P.W., Naka, J., 2002. Submarine alkalic

through tholeiitic shield-stage development of Kılauea Volcano,

Hawai‘i. Geophys. Monogr. Am. Geophys. Union 128, 193–219.

Smith, J.R., Malahoff, A., Shor, A.N., 1999. Submarine geology of

the Hilina slump and morpho–structural evolution of Kılauea

Volcano, Hawai‘i. J. Volcanol. Geotherm. Res. 94, 59–88.

Smith, D.K., Long, L.S.I., Johnson, K.T.M., Reynolds, J.R., 2002.

Volcanic morphology of the submarine Puna Ridge, Kılauea

Volcano. Geophys. Monogr. Am. Geophys. Union 128, 125–142.

Smith, J.R., Satake, K., Suyehiro, K., 2002. Deep-water multibeam

sonar surveys along the southeastern Hawaiian Ridge. Geophys.

Monogr. Am. Geophys. Union 128, 3–9.

Stearns, H.T., 1966. Geology of the State of Hawai‘i. Pacific books,

Palo Alto, CA. 266 pp.

Stearns, H.T., Clark, W.O., 1930. Geology and water resources of the

Kau District, Hawai‘i. U.S. Geol. Surv. Water-Supply Pap. 616,

1–94.

Stearns, H.T., Macdonald, G.A., 1946. Geology and Ground Water

Resources of the Island of Hawai‘i. Hawai‘i Div. Hydrol. Bull.,

vol. 9, 363 pp.

Swanson, D.A., Duffield, W.A., Fiske, R.S., 1976. Displacement of the

south flank of Kılauea volcano: the result of forceful intrusion of

magma into the rift zones. U.S. Geol. Surv. Prof. Pap. 963, 39 pp.

Takahashi, E., Lipman, P.W., Garcia, M.O., Naka, J., Aramaki, S.,

2002. Hawaiian volcanoes: deep underwater perspectives. Geo-

phys. Monogr. Am. Geophys. Union 128, 418 pp.

Teanby, N., Laj, C., Gubbins, D., Pringle, M., 2002. A detailed

paleointensity and inclination record from drill core SOH1 on

Hawai‘i. Phys. Earth Planet. Inter. 131, 101–140.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108 107

Thurber, C.H., Gripp, A.E., 1988. Flexure and seismicity beneath the

south flank of Kılauea Volcano and tectonic implications.

J. Geophys. Res. 93, 4271–4278.

Thurber, C.H., Li, Y., 1989. Seismic detection of a low-velocity layer

beneath the southeast flank of Mauna Loa, Hawai‘i. Geophys.

Res. Lett. 16, 649–652.

Tilling, R.I., Dvorak, J.J., 1993. Anatomy of a basaltic volcano.

Nature 363, 125–133.

Tribble, G.W., 1991. Underwater observations of active lava flows

from Kılauea Volcano, Hawai‘i. Geology 19, 633–636.

Walker, G.W., 1969. Geologic Map of the Kau Desert Quadrangle,

Hawai‘i. U.S. Geol. Survey Map, vol. GQ-827.

Walter, T.R., Troll, V.R., 2003. Experiments on rift zone evolution in

unstable volcanic edifices. J. Volcanol. Geotherm. Res. 127,

107–120.

Wise, W.S., 1982. A volume-time framework for the evolution of

Mauna Kea Volcano, Hawai‘i [abs.]. EOS Trans. AGU 63, 1137.

Wolfe, E.W., Morris, J.D., 1996. Geologic Map of the Island of

Hawai‘i. U.S. Geol. Survey Misc. Invest. Map, vol. I-2524.

Wood, H.O., 1914. On the earthquakes of 1868 in Hawai‘i. Bull.

Seismol. Soc. Am. 4, 169–203.

Wright, T.L., 1971. Chemistry of Kılauea and Mauna Loa lava in

space and time. U. S. Geol. Surv. Prof. Pap. 735, 49 pp.

Wyss, M., 1988. A proposed source model for the great Ka’u,

Hawai‘i, earthquake of 1868. Bull. Seismol. Soc. Am. 78,

1450–1462.

Yokose, H., Lipman, P.W., 2004. Emplacement mechanism of the

South Kona submarine slide complex, Hawai‘i Island: sampling

and observations by ROV Kaiko. Bull. Volcanol. 66, 569–584.

P.W. Lipman et al. / Journal of Volcanology and Geothermal Research 151 (2006) 73–108108