Glacier-clad volcanoes

Glaciers in an Environmental Context
Natural hazards in glacierized regions:
Glacier-clad
volcanoes
Contribution by Demian Schneider
Eyjafjallajökull, Iceland, April 2010
Overview
1. Distribution of glacier-clad volcanoes (worldwide)
2. Volcano-ice interactions
3. Pyroclastic flows
4. Lahars
5. Hazard assessment
6. Examples of volcano-ice interactions
a) Mt. St. Helens
b) Mt. Redoubt
c) Iliamna
d) Popocatépetl
e) Nevado del Ruíz
f) Nevado del Huila
g) Ruapehu
h) Vatnajökull
7. Influence of glacial retreat on volcanoes
1. Distribution of glacier-clad volcanoes
 Intersection of volcanoes/cryosphere
Active volcanoes with relatively large ice masses:
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•
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Alaska
Rocky Mountains
Mexico
Andes
Kamtchatka
Japan
New Zealand
Iceland
1. Distribution of glacier-clad volcanoes
Magnitude of volcanic eruptions
USGS
2. Volcano-ice interactions
 How can volcanoes interact with ice, firn & snow?
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Pyroclastic flows:
Melting and mixing with ice/snow

Lahars
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MOST DANGEROUS!
Lava flows:
Surficial interaction with ice/snow

Lahars (usually less hazardous)
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Geothermal heat flow / subglacial eruptions:
Basal melting, accumulation of subglacial meltwater

flood waves (Jökulhlaup)

slope instabilities / avalanches
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Ash & lava ejection:
In-/decreased ablation

low short-term hazard; long-term reduction of ice & snow volume or
conservation of ice (burried ice)
3. Pyroclastic flows
pyr = fire, klastós = broken Nuée ardente („glowing cloud“)
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Solid matter-gas dispersion (ash & rock fragments)
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Velocity > 400 km/h
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Temperature 300 – 1000°C
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Vesuv, 79 n. Chr., Pompeji (~10‘000 victims)
Mont Pelé, Martinique, 1902, Saint-Pierre (~30‘000 victims)
Mt. St. Helens, 1980 (57 victims)
Mayon, Philippines (1984)
3. Pyroclastic flows
Pinatubo, Philippines (1991)
Unzen, Japan, 1990-1995
PLINIAN ERUPTIONS:
- after Pliny the Younger
AD 79 Vesuv eruption (Pompeij)
- e.g. stratovolcanoes (ring of fire)
- rhyolitic silicate-rich lava
- (melt-) water can enhance tendency
for plinian eruptions
phreatic eruptions
4. Lahars
From Merapi volcano, Indonesia
4. Lahars
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Definition: Mudflow composed by varying proportions of volcanic
sediments and water. Lahars are the most far-reaching deadly volcanic
hazards.
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Grain sizes and water content can vary strongly:
a)
b)
water > 50 vol % 
water < 50 vol% 
hyperconcentrated flow
debris flow
Concentration of fines in lahars usually higher than in non-volcanic debris flows:
 more viscous flow behavior
 friable/loose material on volcanoes usually nearly unlimited!
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Velocities > 100 km/h
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Reach > 100 km
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Temperatures from ‚cold‘ to ‚hot‘ (not boiling)
4. Lahars – trigger mechanisms
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Primary lahars (in direct relation with volcanic eruptions):
a)
b)
c)
d)
pyroclastic flows melting ice & snow or mixing with water
by basal melting of glaciers during eruptions
by surficial interaction with lava flows
by ejected/destroyed crater lakes
Number of events
50
40
30
Pyroclastic flows, …
Basal melting
Cause unknown
Surficial lava flows
Ejected crater lakes
20
10
0
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Secondary lahars (at a later stage, not related to an eruption):
a)
b)
c)
by heavy thunderstorms on unconsolidated pyroclastic or ash deposits
in relation to seasonal melting of snow/ice
by lake outbursts
5. Hazard assessment
Important points:
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Recognition of possible interactions within the volcano-glacier system
 very dynamic environment
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Ice-clad volcanoes present high hazard potentials for devastating
catastrophies:
 Reach, Intensity and destruction potential of individual phenomena versus
population density/infrastructure is critical (risk analysis)!
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Consequences of volcanic activity on glaciers:
 Downstream ecosystems, water supply/agriculture, scenery/tourism
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Between volcanology and glaciology:
 interdisciplinary, problem of missing expertise
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Time-dimensions of volcanoes and glaciers / snow cover:
 often different (geologically, historically, at the moment/in future)
5. Hazard assessment
Two main approaches for hazard assessments of (ice-clad) volcanoes:
1. „Past is the key to the future“:
Assumption that future eruptions generally follow the behavior of past eruptions.
 knowledge of volcanic history:
- characteristics & frequency of eruptions (explosivity, regularities?)
- preferential flow paths
- reach & deposition thickness of ash, pyroclastic flows, lahars, etc.
2. Permanent monitoring (real time):
Prediction of volcanic activity/eruptions by seismic, geodetic, geochemic, thermic,
visual, and remote sensing methods
 long term monitoring  ~precise prediction of eruptions!
Similar approaches for glaciers.
!!! Detection of possible hazard combinations (process chains) between
volcanoes & glaciers. Probability of occurrence (periods)!!!
e.g. Jökulhlaups, failure of glaciers, favoring of plinian/phreatic eruptions through meltwater input…
6a. Examples: Mt. St. Helens (USA), 1980
6a. Examples: Mt. St. Helens (USA), 1980
- 400 m
Mt. St.Helens, prior to and after the catastropic eruption on May 18, 1980
6a. Examples: Mt. St. Helens (USA), 1980
Mt. St.Helens, prior to and after the catastropic eruption on May 18, 1980
~100 Mill. m3 snow & ice in the failing mass
6a. Examples: Mt. St. Helens (USA), 1980
2950 m a.s.l.
2549 m a.s.l.
6a. Examples: Mt. St. Helens (USA), 1980
…and the story goes on…
March 21, 1982
February 22, 2005:
new dome (‚spine‘) & crater glacier
6a. Examples: Mt. St. Helens (USA), 1980
Conclusion from the Mt. St. Helens eruption:
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Consideration of ‚worst-case‘ scenario: sector-collapse
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Glaciers were relatively stable against tectonic stress
earthquake-induced fissures can ‚heal‘
rock is cumulatively weakened by earthquakes
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Filling up of magma chambers ‚inflates‘ volcanoes
oversteepened flanks
Instability / collapse
can be measured (geodesy, inclinometry, remote sensing)
sign for possible forthcoming eruption
6b. Examples: Redoubt (Alaska), 1989
6b. Examples: Redoubt (Alaska), 1989
R. McGimsey
T. Miller
C. Gardner, 1989
6b. Examples: Redoubt (Alaska), 2009
Redoubt
AVO/USGS, March 31, 2009
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Fall 2008:
volcanic activity increases
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05.11.2008:
„Aviation Color Code“ to yellow
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25.01.2009:
„Aviation Color Code“ to orange
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13.02.2009:
AVO 24h- / 7 day service
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10.03.2009:
reduction of seismic activity & geothermal heat flow, gas
emissions unchanged, „Aviation Color Code“ yellow again!
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15.03.2009:
increase of seismic activity, „Aviation Color Code“ orange again,
first ash emissions
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22.03.2009:
series of 5 explosive eruptions, „Aviation Color Code“ red!
Higher water discharge at Drift valley  Lahars
6b. Examples: Redoubt (Alaska), 2009
AVO/USGS, March 21, 2009
AVO/USGS, March 23, 2009
AVO/USGS, March 23, 2009
AVO/USGS, March 23, 2009
6b. Examples: Redoubt (Alaska), 2009
AVO/USGS, March 23, 2009
AVO/USGS, March 23, 2009
6c. Examples: Iliamna (Alaska)
6c. Examples: Iliamna (Alaska)
Fumaroles & enhanced geotherm. heat flow:
Photo: AVO 2004
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Enhanced melting of snow and ice, generation
of small-medium debris flows
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Reduction of basal shear forces below glaciers
 ice avalanches
6c. Examples: Iliamna (Alaska)
Red glacier rock-ice avalanche, 2003
Red Glacier rock-ice avalanche, 2008
6d. Examples: Popocatépetl (Mexiko)
increased
ablation
insulation effects
6d. Examples: Popocatépetl (Mexiko)
Activity 1994-2001: pyroclastic flows melted
ice
6d. Examples: Popocatépetl (Mexiko)
Hazard map
Ashfall, volcanic bombs, pyroclastic flows, lahars
 ~30 Mill. inhabitants within 70km circumference (Mexico City & Puebla)
 Possible evacuation (information, organisation, panic prevention, routes)
 Problem with false alarms or too early warning (return)
6e. Examples: Nevado del Ruíz (Col), 1985
6e. Examples: Nevado del Ruíz (Col), 1985
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Nov. 84:
volcanic activity starts
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July 85:
surveillance starts
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Sept. 85:
phreatic eruption (due to meltwater), no lahars
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Oct. 85:
Risk assessed, hazard zones mapped
no measures by the authorities
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Nov. 13, 85:
Pyrocl. flows of a medium-sized eruption melt snow & ice (~10%)
various lahars, up to 100 km distance
destruction of Armero (70km from crater), >22‘000 casualties!
6e. Examples: Nevado del Ruíz (Col), 1985
Nov. 13, 1985
Gualí Valley, R. Janda, Dez. 18, 1985
Gualí Valley, N. Banks, Dez. 18, 1985
J. Marso, late Nov. 1985
6e. Examples: Nevado del Ruíz (Col), 1985
Armero, R. Janda, USGS
6e. Examples: Nevado del Ruíz (Col), 1985
Conclusion from the Armero disaster:
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Even small or medium sized eruptions can have catastrophic
consequences
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Tragic example of failures in prevention and early warning due to
limitations in institutional coordination
(mainly on the part of local authorities & central government)
communication & information (science – authorities – population)
prevention
6f. Examples: Nevado del Huila (Kol), 2007/08
6f. Examples: Nevado del Huila (Kol), 2007/08
6g. Examples: Ruapehu (NZ)
6g. Examples: Ruapehu (NZ)
Lahars from crater lakes & volcano-ice interaction
Sept . 26, 1995
6c. Examples: Ruapehu (NZ)
Endangering lifes, infrastructure and tourism
Sept. 28., 2007
Some weeks after the eruption
Sept. 28, 2007
6h. Examples: Vatnajökull (Iceland)
6h. Examples: Vatnajökull (Iceland), 1996/2004
Photo: M.T. Magnusson, Nov. 2, 2004
ice cauldron
Tuya-volcano („Tafelvulkan“) Herdubreid in Iceland
Grimsvötn/Gjálp (below Vatnajökull ice cap), Nov. 1996, 1998
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Geothermal activity  large subglacial water reservoirs
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At hydrostatic pressure point  outburst (Jökulhlaup)
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Inundation of sandur plain  destruction of a bridge
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Peak discharge 45‘000 m3/s (historic Katla-Jökulhlaups up to 400‘000 m3/s!)
Grimsvötn/Gjálp, Nov. 1, 2004:
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Drainage system open  continous outflow of water  no Jökulhlaup
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Airspace for entire North Atlantic to Norway temporary closed
7. Influence of glacial retreat on volcanoes
SonntagsZeitung, April 25, 2010
Ruapehu, NZ, 1996