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Volcanic Eruptions: How Wet? How Hot? How Fast?
Terry Plank, Lamont-Doherty Earth Observatory of Columbia University
Pavlof Volcano, Alaska March 27, 2016
15 Volcanoes Erupting or in a State of Eruption/Unrest Now
Where are the erupting volcanoes?
Mayon Volcano, Philippines Over 90,000 people evacuated
VEI = Volcanic Explosivity Index order of magnitude scale: 0 - 8
• eruptive mass • plume height • duration
How to Quantify Volcanic Explosivity?
VEI = 1-2 �Strombolian� gentleAnak Krakatau (4. - 7. June 2009)
http://www.swisseduc.ch/stromboli/perm/krakatau/night-on-anak-krakatau-en.html
MSH - what about Pelee, Vesuvius, Krakatau??
VEI = 2-3 explosive, severeAnatahan, Marianas Islands: May 2003
Photograph by Heilprin, 1902 ttp://www.swisseduc.ch/stromboli/perm/guadeloupe-martinique/pelee-geology-en.html
VEI = 4 cataclysmicMt. Pelee, Martinique, 1902: 29,000 fatalities
VEI = 8 �super-volcano!�Yellowstone, 600,000 yrs ago
VEI 7 (100 km3) Tambora, 1815, Indonesia
1000 km3
Last%“super+volcano”%erup2on:%26,000%yrs%ago,%NZ%
Melt Inclusions May Preserve Undegassed H2O
0 1 2 3 4
0 1 2 3 4 0 200 400 600 800
H2O
CO2
H2O (wt%) in melt CO2 (ppm) in melt Pr
essur
e (kb
)
0 4 8 12 16
Depth (km)
degassed magma
Closed-system degassing from VolatileCalc (Newman and Lowenstern, 2001)
melt inclusion ~ 50 microns
olivine
Erik Hauri & Ion Microprobe, Carnegie Institution of Washington
Spots analyzed with: • ion microprobe, • electron microprobe • laser ablation ICPMS
Scoria'('Yes!'Bombs,
Boo!
< 2 cm lapilli
(and ash) YES!
Lloyd et al. (2012) CMP– water loss from clasts of different size
NSF/GeoPrisms+AVO/USGS+Deep%Carbon%Obs.%Joint%Expedi2ons%
2016%Team%on%the%Mari2me%Maid%with%the%Mari2me%Helicopter%
“Slab'to'the'Surface”'
First Volcanic Gas Data in the Western Aleutians (2015) DCO/DECADE/GeoPrisms (Tobias Fischer, Taryn Lopez, Cynthia Werner, Christoph Kern)
Kiska%
Seguam Volcano (Alaska), 1977 Eruption
0 100 200 300 400 500 600
0 1 2 3 4 H2O (wt%)
CO2 (p
pm)
8 km 4 km
2 km Ascent
olivine-hosted melt inclusions
From Zimmer et al. (2010) J. Pet.
max
0 2 4 6 8
10 12 14
1 N = 56 volcanoes, 7 arcs, maximum H2O
Maximum H2O (wt%)
n
Why do Most Mafic Arc Magmas Have 4 +/-1 wt% H2O?
3.9 +/- 0.4 arc average 3.9 +/- 1.2 volcano average
2 3 4 5 6 7
0
1
2
3
4
5
6
1 2 3 4 5 6
VEI
(Vo
lcanic
Exp
losivi
ty In
dex)
H2O wt% in pre-eruptive magma
No Obvious Relationship between Eruptive Intensity and Pre-Eruptive H2O
Akutan 340 CE
Seguam 1977
C.Negro 1992
Fuego 1974 Arenal ET3
Okmok 1997
Shishaldin 1999
Irazu 1723
Why does the rate of magma rise matter?
1. Bubble-liquid segregation and bubble coalescence
high ascent rate
2. Bubble number density
3. Shear heating along conduit walls
low ascent rate
Also:%Bri[le%failure,%microlites,%diseq%degassing%
bubble%are%white%here%
bubble%are%black%here%
bubble%are%white%here%
bubble%are%black%here%
bubble%are%white%here% bubble%are%white%here%
Thermal Diffusion and Turkeys
With credit to England, Molnar and Richter, 2007
the turkey the ice-box
180°F
32°F
20 minutes
2 cm
80 minutes
4 cm