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: 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? Pyroclastic flows: Melting and mixing with ice/snow Lahars Lava flows: Surficial interaction with ice/snow Lahars (usually less hazardous) MOST DANGEROUS! Geothermal heat flow / subglacial eruptions: Basal melting, accumulation of subglacial meltwater flood waves (Jökulhlaup) slope instabilities / avalanches 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 ) Solid matter-gas dispersion (ash & rock fragments) Velocity > 400 km/h Temperature 300 1000 C 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 Definition: Mudflow composed by varying proportions of volcanic sediments and water. Lahars are the most far-reaching deadly volcanic hazards. Grain sizes and water content can vary strongly: a) water > 50 vol % hyperconcentrated flow b) water < 50 vol% 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! Velocities > 100 km/h Reach > 100 km Temperatures from cold to hot (not boiling)
4. Lahars trigger mechanisms Primary lahars (in direct relation with volcanic eruptions): a) pyroclastic flows melting ice & snow or mixing with water b) by basal melting of glaciers during eruptions c) by surficial interaction with lava flows d) by ejected/destroyed crater lakes Number of events 50 40 30 20 10 0 Pyroclastic flows, Basal melting Cause unknown Surficial lava flows Ejected crater lakes Secondary lahars (at a later stage, not related to an eruption): a) by heavy thunderstorms on unconsolidated pyroclastic or ash deposits b) in relation to seasonal melting of snow/ice c) by lake outbursts
5. Hazard assessment Important points: Recognition of possible interactions within the volcano-glacier system very dynamic environment 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)! Consequences of volcanic activity on glaciers: Downstream ecosystems, water supply/agriculture, scenery/tourism Between volcanology and glaciology: interdisciplinary, problem of missing expertise 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. m 3 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: Consideration of worst-case scenario: sector-collapse Glaciers were relatively stable against tectonic stress earthquake-induced fissures can heal rock is cumulatively weakened by earthquakes 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 Fall 2008: volcanic activity increases 05.11.2008: Aviation Color Code to yellow 25.01.2009: Aviation Color Code to orange 13.02.2009: AVO 24h- / 7 day service 10.03.2009: reduction of seismic activity & geothermal heat flow, gas emissions unchanged, Aviation Color Code yellow again! 15.03.2009: increase of seismic activity, Aviation Color Code orange again, first ash emissions 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) Photo: AVO 2004 Fumaroles & enhanced geotherm. heat flow: Enhanced melting of snow and ice, generation of small-medium debris flows 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)
6d. Examples: Popocatépetl (Mexiko) increased ablation insulation effects 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 Nov. 84: volcanic activity starts July 85: surveillance starts Sept. 85: phreatic eruption (due to meltwater), no lahars Oct. 85: Risk assessed, hazard zones mapped no measures by the authorities 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!
Gualí Valley, N. Banks, Dez. 18, 1985 J. Marso, late Nov. 1985 6e. Examples: Nevado del Ruíz (Col), 1985 Nov. 13, 1985 Gualí Valley, R. Janda, Dez. 18, 1985
6e. Examples: Nevado del Ruíz (Col), 1985 Armero, R. Janda, USGS
6e. Examples: Nevado del Ruíz (Col), 1985 Conclusion from the Armero disaster: Even small or medium sized eruptions can have catastrophic consequences 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 Sept. 28, 2007 Some weeks after the eruption
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 Geothermal activity large subglacial water reservoirs At hydrostatic pressure point outburst (Jökulhlaup) Inundation of sandur plain destruction of a bridge Peak discharge 45 000 m 3 /s (historic Katla-Jökulhlaups up to 400 000 m 3 /s!) Grimsvötn/Gjálp, Nov. 1, 2004: Drainage system open continous outflow of water no Jökulhlaup Airspace for entire North Atlantic to Norway temporary closed
7. Influence of glacial retreat on volcanoes SonntagsZeitung, April 25, 2010
Ruapehu, NZ, 1996