1 / 48 Volcanic Hazards

2 / 48 Volcanic Hazards Direct –Lava Flows –Eruptions / Explosions –Pyroclastic Flows –Ashfall –Mudflows/Lahars –Gas –Caldera Collapse –Tsunami Indirect –Famine –Climate change

3 / 48 Volcanic Hazards Volcano Fatalities Last 500 Years Type of Event275,000 deaths530 Volcanic Events Pyroclastic flow29%15% Tsunami21%5 % Lahar15 %17 % Indirect (famine)23 %5 % Gas1 %4 % Lava flow<1 %4 % Pyroclastic fall (bombs) 2 %21 % Debris avalanche2 %3 % Flood1 %2 % Earthquakes<1 %2 % Lighting<1 %1 % Unknown7 %20 %

4 / 48 Lava Flows Nyiragongo, Zaire 2002 –In East African Rift Zone –Lavas unusually low in SiO 2 –Flowed rapidly down the slope, through the city of Goma to Lake Kivu –45 people killed

5 / 48 Lava Flows Iceland –Icelandic-type Eruptions AKA fissure eruptions Peaceful Basaltic magma

6 / 48 Lava Flows Iceland –Lava Flows of /23/73 fissure opened up near the town of Vestmannaeyjar (pop. 5,300) Lava flows and pyroclastic debris threatened to bury the town Townspeople sprayed seawater on lava, diverted the flow Town saved

7 / 48 Heimaey Eruption

8 / 48 Eruptions / Explosions Lassen Peak, California, –Lava Dome –Formed after Mt. Tehama became extinct & eroded away –Part of the Lassen dome field

9 / 48 Eruptions / Explosions Lassen Peak, California, –Began erupting May 1914 July 18, 1914 – Huge ash cloud ejected 3,350 m into atmosphere May 16 – 18, 1915 – Lava oozed out of crater –Red glow from the hot lava visible at night 34 kilometers away. May 19, 1915 – avalanche of hot rocks combined with snow and triggered a lahar that extended more than 50 km Eruptions continued through 1917, then ceased

The northeast flank of Lassen Peak photographed on 22 May 1915 by B.F. Loomis from the position marked on Fig. 5, several hours prior to the 22 May eruptions. Peaks labeled A and B can be used as registration points when comparing Fig. 2a and Fig. 3. The label "hot rock" was written on the original glass plate by Loomis over the image of a piece of 19 May dacite lava and alludes to the fact that the rock was still too hot to touch ~48 hr after it was erupted. From: 3

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13 / 48 Eruptions / Explosions Mount St. Helens, Washington, 1980 –March 20, 1980 – Harmonic tremors began Lava dome pushed into the north flank, over-steepening it –May 18, earthquake on nearby fault Caused a massive landslide on the unstable north side Removal of overburden released pressure and caused the eruption –5-10 fatalities, $12.3 million in damage

14 / 48 Mt. St. Helens before the 1980 eruption

15 / 48 Mt. St. Helens following the 1980 eruption

16 / 48 Mt. St. Helens Rock Glacier Dome New Dome Vent

17 / 48 Mt. St. Helens, October 1,

Mt. St. Helens Blast Zone June 28, 2012 © Sonjia Leyva, / 48

19 / 48 Comparison of Large Volcanic Eruptions

20 / 48 Pyroclastic Flows Mount St. Helens, Washington, 1980 –Pyroclastic flows (Nueé ardentés) are mixtures of hot gas and ash that move very quickly along the ground

21 / 48 Pyroclastic Flows Mount Mayon, Philippines, 1968 El Chichon, Mexico, 1982 Mount Unzen, Japan, 1991 Mont Pelee, , Mont Pelee, Martinique, 1902 Krakatau, Indonesia, 1883

22 / 48 Pyroclastic Flows Mount Shasta, California –Second tallest in the Cascade Range –Erupted 11 times over last 3,400 years 3 times last 750 Last eruption

23 / 48 Pyroclastic Flows Mount Shasta, California –Slopes covered with pyroclastic flows such as lahars –Event 300,000 years ago deposited 8x amount of debris as did the Mt. St. Helens 1980 event

24 / 48 Mt. Shasta – November 1998

25 / 48 Ashfall Huge areas may be covered by volcanic ash Damage to urban areas can be enormous –Crops are destroyed threatening the food supply –Public water contaminated –Buildings collapse under weight of ash –Air travel disrupted

26 / 48 Ashfall

27 / 48 Lahars (Volcanic Mudflows) Ways that volcanoes make lahars –Add water + volcanic material = lahar –Water sources: Melt glaciers Displace lakes Rain –Material Ash Soil Burnt vegetation

28 / 48 Lahars (Volcanic Mudflows) Kelut, Indonesia, 1586, 1919 –Large crater lake at summit –Pyroclastic eruptions + water from lake = lahar Eruptions make for fertile soil, so heavily populated –Last eruption: 1990 VEI=4 produced a large cloud and heavy tephra fall 32 people killed

29 / 48 Lahars (Volcanic Mudflows) Mount St. Helens, Washington, 1980 –Mudflow was caused by the displaced Spirit Lake Mudflow went 60 miles to the Columbia River 45 million cubic yards sediment entered Columbia River

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31 / 48 Surface details of the debris (mud) flow on the North Fork of the Toutle River near Coldwater Creek (see map). There is approximately 50 feet of relief between the pond and the mudflow surface. Devastation occurring at the log camp on the South Fork Toutle River - overturned trucks and caterpillers. tion.html

32 / 48 Lahars (Volcanic Mudflows) Nevado Del Ruiz, Colombia, 1985 –2 eruptions on Nov 13, 1985 melted the summit glaciers –Mudflows travelled in all directions from the summit –Mud traveling 30 mph and 50 feet deep buries Amero 30 miles away –25,000 killed

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34 / 48 Lahars (Volcanic Mudflows) Mount Rainier, Washington –Mudflows threaten the towns and villages blow this dangerous volcano –Evacuation plans and drills are the key to survival

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36 / 48 Gas Cameroon –Type of volcanism: Maar A volcanic crater that is produced by an explosion in an area of low relief, is generally more or less circular, and often contains a lake, pond, or marsh. ( Landsat image of Lake Nyos processed by Sarah Sherman, April 2000.

37 / 48 Gas Cameroon –August of 1986 Lake Nyos 1 km of CO 2 released ~1700 people killed up to 26 km away from the lake –August of 1984 smaller gas burst from Lake Monoun 37 people killed

38 / 48 Gas Cameroon –Only three lakes in the world are known to contain high concentrations of dissolved gas in their bottom waters: Lakes Nyos and Monoun in Cameroon and Lake Kivu in East Africa. –Only Lakes Nyos and Monoun are known to have recently released gas resulting in the loss of human life. Using Science to Solve Problems: The Killer Lakes of Cameroon By Dr. George Kling

Gas Release (CO 2 ) Lake Nyos, Cameroon 39 / 48

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42 / 48 Caldera Collapse Believed to be caused by magma evacuating its chamber Caldera eruptions in New Zealand could damage cities like Auckland Famous (or infamous) collapsed calderas: –Crater Lake, Oregon –Yellowstone, Wyoming –Long Valley Caldera, California –Krakatoa & Toba, Indonesia

43 / 48 Tsunami Mt. Unzen, Japan 1792 –Earthquake caused lava dome to collapse –Traveled 6.4 km to ocean, caused tsunami –15, 000 people killed

44 / 48 Southeastern view of Unzen Volcano from air Taken by Nakagasaki Photo Service Co. LTD (Oct.1992) tokyo.ac.jp/unzen/bgd.htm

45 / 48 Indirect – Famine Laki, Iceland Fissure Eruption of 1783 –Large quantities of SO2 and fluorine –Killed 75% of Iceland’s sheep & horses 50% of Iceland’s cattle 20% of Iceland’s population (due to famine)

46 / 48 Indirect – Famine Tambora, Indonesia, 1815 –Pyroclastic fallout destroyed crops in Indonesia –Affected global climate – 1816 “year without a summer”

47 / 48 Volcano Monitoring and Warning Long Valley, California, 1982 Mount Pinatubo, Philippines, 1991

48 / 48 End