Volcanology

dr Monika Nowak

Poznań, 2019

Encyklopedia of Volcanoes

Magma Formation and Migration

Fundamentals of physical volcanology

VOLCANIAN TYPE OF ERUPTION

https://www.youtube.com/watch?v=E4j-PGiSYQI

Type of

eruption

Commonly

observed

phenomena Lavas

Pyroclastic deposits

(Composition) Typical volcanic landforms

hawaiian

fire fountains >100 m

high, lava lake, lava

tubes

close to basalt in

composition

small amounts of Pele'

hair/tears

basaltic shield volcano,

fissure eruptions, summit

caledra, spatter cone, lava

flows (pahoehoe, a'a),

levees

strombolian

periodic explosions

emitting scorai/ash

clouds

basalts ora

basaltic andesites

- rarly more acid

composition well sorted scoria beds

scoria cone (bombs-bloks),

fissure eruptions

vulcanian

discrete expolsions,

short-lived eruption

column 5-10 km

high

composition

intermediate to

acid

thin beds of ash, bread-

crust bombs, lithics crater

sub-pilnian

sustained eruption

column 10-20 km

high, PDCs

usually dacite,

rholite or

phonolite

widsperad pumice fall

blanket

stratovolcano, crater

(caldera subsidence)

pilnian and

ultrapilnian

sustained eruption

column 20-50 km

high, umbrella PDCs

usually dacite,

rholite or

phonolite

pumiceous lapilli

tuff/ignimbrite

stratovolcano, crater -

caldera subsidence

hydrovolcanic

repeted expolsions,

"cock's tail" ash

cloud, expanding

base-surge cloud often basalts

thin beds of juvenile ash,

and/or country rocks

lithicks; cross-stratified

base-surge deposits

tuff or ash ring, crater or

maar

http://oceanexplorer.noaa.gov/explorations/02fire/background/plan/media/plate.html

Rocks

Volcanic rock chemical classifications

TAS – (total alkali silica)

37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

Na 2

O +

K2O

[wt%

]

SiO2 [wt. %]

Rhyolite

Dacite

Trachyte

Trachydacite

Trachy-

andesite

AndesiteBasaltic

Andesite

Trachy-

basalt

Basaltic

Trachy-andesite

Basalt

Picro-

basalt

Tephrite

Basanite

Phonotephrite

Tephriphonolite

Phonolite

Foidite

Igneous Rocks A classyfication and Glossary of terms R.W. Le Maitre

https://wwwf.imperial.ac.uk/earthscienceandengineering/rocklibrary/viewrecord.php?cID=5403

Andesite - Viti Levu, Fiji

Pictures from Rock Library Imperial College

https://wwwf.imperial.ac.uk/earthscienceandengineering/rocklibrary

/viewrecord.php?cID=5403

LANDFORMS – TYPES OF

VOLCANOES

http://canarygeog.canaryzoo.com

https://www.youtube.com/watch?v

=PJeTY1Eg-0o

Movie:

www.qualityplanning.org

Lavas

(Lava domes)

Volcanic sucession – Cas, Wright 1992

Lava domes

Volcanic sucession – Cas, Wright 1992

Lava domes – classyfication after Blake 1999

Volcanoes Francis, P., Oppenheimer, C. 2004

Showa Sin-Zan Lava Dome, Japan -- The Showa Sin-Zan (New Roof

Mountain) grew as a single mass of lava that was pushed upward like a piston.

This upheaved plug rose steadily from January 1944 to November 1944.

Courtesy of Peter Francis.http://www.geology.sdsu.edu/

Upheaved plug

Volcanology and Geothermal Energy, Kenneth Wohletz, Grant Heiken 1992

Forms of endogenous and exogenous domes, showing various fracture foliations. (a) Upheaved,

exogenous dome similar to that illustrated in Fig. 5.1. (b) Peléean dome showing vent spines,

blocky fracture, and development of talus aprons. (c) Detail of vent spine of Mont Pelée

(from Lacroix, 1904)(d) Exogenous dome that discharges viscous flow lobes from a summit vent. (e)

Intrusive dome in which viscous magma body is emplaced just below the earth's

surface and maintains a carapace of upwarped strata.

(Adapted from Williams and McBirney, 1979.)

Cryptodome

Volcanic sucession – Cas, Wright 1992

Organy Wielisławskie

Coulées are a hybrid between a lava dome and a lava flow. In order to get the

thick and sticky lava to flow, this type of dome is generally erupted on steep

slopes which allow the lava to ooze slowly down the slope. Typically they do not

flow more than a few kilometers, though some larger examples have traveled well

over 10km. As a neat feature of coulées, huge pressure ridges, known as

Ogives, are often seen on the outer surface of the flow.

Coulées

http://volcano.oregonstate.edu/book/export/html/443

The most famous dacite lava flow – Chao, Chile

One of the best known examples of a coulée, and the largest

of its type in the world, is the Chao dacite (Figure M4, a&b),

occupying the saddle between Paniri and Léon volcanoes

(Guest & Sanchez, 1969; de Silva et al., 1988). 39Ar-40Ar

ages indicate it is less than 100,000 years old (Drake et al.,

unpub. data, 1989). It is a 14.5 km long coulée, with flow

fronts 350-400 m high and has a total erupted volume of ~26

km3. A characteristic feature of this body are the prominent

30 m high flow ridges or ogives on its surface, resulting from

folding during emplacement of surface layers with different

mechanical properties due to differential cooling of the lava.

Eruption of the huge coulée appears to have occurred in two

main stages; 1) explosive eruption of a small volume of

dacitic ignimbrites (<1 km3) followed by passive effusion of

the main mass of lava (Chao I and II) which constitutes 22

km3; and 2) explosive eruption of small rhyolitic airfall and

formation of a dense pumice cone followed by passive

effusion of Chao III (~3 km3). The lava is high-K, very

porphyritic, and thought to have erupted over a period of

100-150 years (de Silva et al., 1994).

http://volcano.oregonstate.edu/oldroot/CVZ/chao/

Guest, Schancez 1969

Guest, Schancez 1969

Volcanic sucession – Cas, Wright 1992

http://library.thinkquest.org/

Spine

Mount St. Helen

PeléeanNamed after the iconic lava dome formed on Mt. Pelee in 1902 (which eventually collapsed resulting

in the destruction of St. Pierre on Martinique), these lava domes are often the steepest sided of all

lava domes. They are typically circular similar to Tortas, but rather than having a flat top, they show

relatively smooth upper surfaces punctuated by tall vertical spines. These vertical spines give these

domes a craggy appearance and also frequently collapse causing talus slopes to frequently

surround these domes. This type of dome is most commonly found associated with larger composite

volcanoes.

http://volcano.oregonstate.edu/book/export/html/443

Spine

Low lava dome - Tortas

Named after their striking resemblance to cake or “Torta”, these domes are common

throughout the world, but especially so in the Andes mountains of South America. This

type of lava dome is generally erupted on mostly flat ground and as a result the lava is

able to push outwards, but not far. They typically are flat-topped and roughly circular.

The thickness and diameter of these domes can vary greatly from a few meters to

nearly a kilometer in thickness and several kilometers in diameter. These domes grow

by internal processes and lava fills in the center of the dome near the vent and pushes

older layers outwards, forming an onion-like internal structure.

http://volcano.oregonstate.edu/book/export/html/443

Pyroclastic deposits

Igneous Rocks A classyfication and Glossary of terms R.W. Le Maitre

What control the eruption column height?

http://www.greendiary.com/mexican-mountain-spits-ashes-rocks-endangering-18-million-people.html

Encyklopedia of Volcanoes

pyroclastic fall The rain

out of clasts through the

atmosphere from an

eruption jet or plume during

an explosive eruption.

Ht is the maximum height

attained by the plume and Hb

is the height at which the

plume density is equal to that

of the surrounding atmosphere

Fragmentation index (F). A parameter measuring the grain size of a pyroclastic

fall deposit, specifically the percentage of ash finer than 1 mm at the point on the

dispersal axis corresponding to 1/10 of the maximum thickness of the deposit.

Dispersal index (D) A measure of the extent of a pyroclastic fall deposit,

specifically the area enclosed by an isopach drawn at 1/100 of the maximum

extrapolated thickness of the deposit.

Thickness half-distance (bt) The ‘‘average’’ distance over which the thickness

of a pyroclastic deposit halves.

Grain size half-distance (bc). The ‘‘average’’ distance over which the maximum

clast size in a pyroclastic deposit halves.

Encyklopedia of Volcanoes

Isopach maps show maximum thickness of a pyroclastic

fall deposits.

Isopleth maps show average maximum pumice or scoria

and lithic size distribution.

Booth et al. (1978)

Encyklopedia of Volcanoes

Shock waves

• https://www.youtube.com/watch?v=E4j-PGiSYQI

https://www.youtube.com/watch?v=BUREX8aFbMs

Bread-crust bombs (panino)

Rounded or angular lumps with a smooth,

galssy crust broken by deep cracks and

fissures, exposing the forthy, vescicular core,

of the bomb, and reminiscent of a well-

baked, crusty loaf of bread.

https://www.youtube.com/watch?v=Nee6zg9azb0

Volcano – google maps

Isla di Vulcano - Wikipedia

Based on webcam data and satellite images, the Darwin VAAC reported that during 13-14 November an

ash plume from Sinabung rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted almost 150 km NW and

W. According to a news article, a pyroclastic flow traveled 1.2 km down the SE flank on 14 November,

prompting more evacuations from villages near the base of the volcano. The article noted that more than

7,000 people had been evacuated from 10 villages.

An explosion observed with the webcam on 18 November produced an ash plume that rose to an altitude

of 7.6 km (25,000 ft) a.s.l. About 30 minutes later an ash plume also visible in satellite images rose to an

altitude of 11.3 km (37,000 ft) a.s.l. and drifted 65 km W. Four hours later satellite images showed ash

plumes at an altitude of 9.1 km (30,000 ft) a.s.l. to the W of Sinabung and at an altitude of 4.6 km (15,000

ft) a.s.l. over the crater. On 19 November the webcam recorded an ash plume that rose to an altitude of

4.6 km (15,000 ft) a.s.l. over the crater. A news article stated that later that night that an ash plume rose to

an altitude of 10 km (32,800 ft) a.s.l.

A news article from 20 November noted that volcanologists updated the hazard map for Sinabung. The

second-tier disaster-prone area, previously defined as a radius of 2-3 km from Sinabung’s crater, was

expanded to 4-5 km.

http://volcano.si.edu/reports_weekly.cfm#vn_211060; http://www.bbc.co.uk/news/world-asia-24124361

Mount Sinabung - Indonesia