Lecture 9: Volcanic Hazards

Transcription

1 Lecture 9: Volcanic Hazards Key Questions 1. What are the dominant primary volcanic hazards? 2. What is the difference between a pyroclastic flow and an ash fall? 3. If Mt. Baker discharged an ash plume, where would it likely drift to and fallout? 4. What volcanic gases are most hazardous to humans and animals? 5. Why is CO 2 dangerous? 6. What is most at risk to lava flows? 7. What are some ways to lower the risk? 8. What is VEI? 9. What is VPI (see In Harms Way Geotimes link)?

2 Volcanic Hazards Mt Pinatubo in the Philippines, June 1991

3 Tectonic Setting determines Magma Composition determines Eruptive Style determines Hazard Type

4 Stratovolcano andesite basalt steep sided layered (pyroclastic material) mainly andesite explosive convergent zones

5 h high lithostatic pressure

6 eruption expansion cause ground deformation heat h expansion causes earthquakes lower lithostatic pressure drop in pressure causes gases to develop gas pressure builds up and explodes!

7 Volcanic Hazards Air-Fall Tephra (ash fall) Lava Flows Pyroclastic Flows (ash flow) Volcanic Gases Landslides Lahars Tsunamis

8 Ash Fall Gardner et al., Potential Volcanic Hazards from Future Activity of Mount Baker, Washington, Open-File Report

9 Plinian Style Hawaiian Style Kilauea Mount St.Helens

10 Volcano Explosivity Index (VEI)

11 Volcano Explosivity Index (VEI) VEI PLUME HEIGHT VOLUME CLASSIFICATION (See Eruption Types) EXAMPLE 0 <100 m 1000s m3 Hawaiian Kilauea m 10,000s m3 Hawaiian/Strombolian Stromboli km 1,000,000s m3 Strombolian/Vulcanian Galeras (1992) km 10,000,000 m3 Vulcanian Ruiz (1985) km 100,000,000s m3 Vulcanian/Plinian Galunggung (1982) 5 >25 km 1 km3 Plinian St. Helens (1980) 6 >25 km 10s km3 Plinian/Ultra-Plinian Krakatau (1883) 7 >25 km 100s km3 Ultra-Plinian Tambora (1815) 8 >25 km 1000s km3 Ultra-Plinian Toba (74 ka)

12 SIZE (cubic km) EXAMPLE FREQUENCY Kilauea, Unzen several months Etna 5 years St. Helens (1980) 10 years 1-10 Pinatubo 100 years Krakatau (1883), Katmai (1912) 1000 years Tambora (1815) 10,000 years >1000 Yellowstone, Toba 100,000 years

13 Ash Hazards Dangerous to aircraft Cause structural damage (heavy!) Can destroy crops Volcanic ash consists of tiny jagged pieces of rock and glass that is hard, abrasive. Can contaminate water and soil May pollute the atmosphere

14 Mt. St. Helens: Ash Discharge

15 Graph showing mean diamater of ash particles with increasing distance from Mount St. Helens volcano. Mt. St. Helens: Ash Discharge

16 Mt. St. Helens: After May 18, 1980

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18 Copyrighted photo courtesy of Douglas Miller Ephrata, Washington, on the morning of May 18, km (145 mi) east of Mount St. Helens.

19 Gardner et al., Potential Volcanic Hazards from Future Activity of Mount Baker, Washington, Open-File Report

20 Gardner et al., Potential Volcanic Hazards from Future Activity of Mount Baker, Washington, Open-File Report

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22 Ash Plume Ash Fall Mt. Pinatubo, Philippines, June 1991 Clark Air Force Base

23 A densely settled area of about 2,000 square kilometers was blanketed by 10 to 25 centimeters of rain-soaked tephra; 189 people were killed by collapsing buildings, and damage to utilities and agricultural lands was extensive. Paladio-Melosantos et al., Tephra Falls of the 1991 Eruptions of Mount Pinatubo

24 Erosional dissection of an ash deposit at Pinatubo volcano

25 Ash particles may absorb these aerosol acid droplets onto their surfaces and contaminate water and soils.

26 Scientists measured a drop in the average global temperature of about 1 o F (0.6 o C) after 15 months.

27 Ash is dangerous for aircraft glass shards can damage and stall engines

28 Volcanic ash particles abrade windows, clog fuel systems, and accumulate in and clog jet engines with molten glass.

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30 Eyjafjallajökull = island mountain glacier Eyjafjallajökull volcano

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35 The International Air Transport Association (IATA) said that at its height, the "crisis" hit almost a third of global flights. It estimated that 1.2 million passengers a day were affected, and global airlines have lost about $1.7billion in revenue.

36 Ash is dangerous for aircraft Remote Sensing Image

37 Remote Sensing Data from the Eyjafjallajökull volcano

38 Lava Flows Cause property damage, but rarely kill people. Travel meters per hour to meters per day depending upon the viscosity and topography. Pahoehoe Basaltic Lava: Kalanpana, Hawaii

39 Aa Basaltic Lava: Iceland

40 Hydrocooling: Iceland

41 Aa Basaltic Lava: Iceland

42 Iceland

43 Mount Etna in Sicily

44 Kilauea, Hawaii

45 Mount Etna in Sicily

46 Pyroclastic Flows or Ash Flows Mayon volcano in the Philippines on September 12, 1984 Pyroclastic flows are mixtures of hot gas and rock that travel gravitationally down the flanks of a volcano at high velocities (up to 100 km/hr)

47 Mayon volcano in the Philippines on September 23, 1984

48 Pyroclastic Flow Mt. Unzen, Japan, June 1991

49 Unzen volcano in southern Japan June 23, 1993

50 Augustine volcano in Alaska on March 30, 1986

51 Soufrière Hills volcano on Montserrat June 25, 1997

52 Mt. Pelee: 29,000 people killed by a pyroclastic flow in Port-au-Prince, Haiti Photograph of the remains of St. Pierre, Martinique (by Heilprin, 1902).

53 Volcanic Gases

54 Volcanic Gases Doug Nathe collecting gases from a fumarole on the floor of Sherman Crater, Aug. 22, Gas samples have been sent off to USGS, Menlo Park, for analysis. Photo by D. Tucker

55 Volcanic Gases Sherman Crater Mt Baker

56 Examples of volcanic gas compositions, in volume percent concentrations (from Symonds et. al., 1994) Volcano Tectonic Style Temperature Kilauea Summit Hot Spot 1170 C Erta` Ale Divergent Plate 1130 C Momotombo Convergent Plate 820 C H C S H CO H 2 S HCl HF Most Dangerous

57 Carbon Dioxide (CO 2 ) Discharge Lake Nyos, Cameroon West Africa, 1986

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59 Carbon Dioxide (CO2) Discharge Lake Nyos, Cameroon West Africa, 1986 Killed 1700 people and 3000 cattle

60 Ash particles may absorb these aerosol acid droplets onto their surfaces and contaminate water and soils.

61 Volcanic Landslides Iriga volcano in the Philippines was produced by a massive landslide during the Holocene.

62 Alaska's Augustine volcano

63 Mt. St. Helens: Just Prior to Eruption This is Harry Glicken who was killed during the eruption of Mt. Utzen, Japan, June However, the geologist occupying this observation site was killed during the May 1980 eruption of Mt St. Helens.

64 Mt. St. Helens: Volcanic Landslide

65 Mt. St. Helens: Volcanic Landslide

66 Mt. St. Helens: Volcanic Landslide

67 Mount Shasta The hummocky landslide deposit was emplaced between 380,000 and 300,000 years ago. Photograph by S.R. Brantley on July 3, 1994

68 VPI Index

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