Chapter_7_Worksheet

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Oct 30, 2023

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Chapter 7 Volcano Case Histories: Killer Events Remember to make sure your answers are in bold font! Volcanism at Spreading Centers • Most volcanism on Earth—almost ___ mi 3 /yr. Iceland—Lava flows of 1973 • Heimaey island—population of ______ See Fig 7.1 o Lava (and ____ flow) directed by construction of wall of ________ material and hardened _______ • Benefits o Island _______ about _______ o ________ improvement o Cooling lava _________ with _______ provided a source of ________ for ________ homes Volcanism at Subduction Zones • Most of world’s ___________ volcanoes are ___________ zone volcanoes • Many regions around subduction zone volcanoes are heavily ___________ • Many erupt directly into ____________ (not underwater) so have _________ impact on worldwide _____________ Cascade Range, Pacific Coast of U.S., and Canada • Very ___________ due to ______-rich, _________ enriched, rhyolite/andesite magmas • Basically, volcanoes are the same _________ but all have their ________ eruptive personalities! See Fig 7.4, 7.5 7.7 • _______________ dating of buried ________ and _______ flows can tell us the _________ of the _________ See Fig 7.9 Mt St. Helens, WA; 1980 See Fig 7.10 and 7.11 • Began with _____________ of earthquakes (one, 5.1M) • Huge _______ occurred when _________ flank “blew apart” --It traveled to ________ Lake creating waves up to ______ ft high and then to _________ River. • Landslide _________ __________ on magma and blast followed resulting in __________ and __________ flows • Lahars formed in rivers valley traveled ____ mph. • Huge _______ in ________ created large _______ blast (Plinian phase) and surge that traveled ______ mph and killed __________ of trees. • Currently, a new ________ _______ is forming. • At least ________ mi 2 affected • ________ deaths • See video clip on the Eruption of Mt. St. Helens: https://www.youtube.com/watch? v=AYla6q3is6w

Lassen Peak, CA; 1914-17 • Not a volcano itself but a ______ _______ • Why did the eruptions occur in May? Mt. Shasta: 14,162 ft high; 2 nd tallest (Rainer 1 st ) • Active volcano- _______eruptions in 3,400 yrs., last in _____. • Should we be worried about another eruption? See Fig. 7.18-7.20 In Greater Depth: Rapid Assembly and Rise of Magma Fig.7.21 Killer Events and Processes Volcanoes kill in different ways—See Fig. 7.22-23 & Table 7.1 • Pyroclastic flows, lahars, tsunami, gas, fragments lava flow, floods, earthquakes, lightning and famine Historic Record of Volcano Fatalities • About ________ people killed during last _______ yrs. by about a __________ volcanic processes. Pyroclastic Flows • Superhot, high speed turbulent cloud of ___, ___ and ___ – can kill thousands of people in one event. • Some famous events include: o Mount Mayon, Philippines, ________ o El Chichon, Mexico, ______ o Mount Unzen, Japan, _______ • Mont Pelee, Martinique, 1902 (Caribbean island) o Town of St. Pierre: about ________ people o _________ on May 10 th to be held o Gov. Mouttet would not let people _____________ o ______________ or “glowing cloud” rushed downward at about _________ mph (1,300 F). o Death caused by: 1) _____________, 2) inhaling superhot ________, or 3) ______________ • _____ survivors • Krakatau, Indonesia, 1883 • Killed ___________+ due to caldera collapse and___________ wave- o _____ than ________ directly killed by ______________ o More than _________killed by volcano-caused tsunami • Can a flow rush across water? o A pyroclastic flow rushed ____ miles to reach Sumatra and killed __________+

Lahars • Mixture of ______________ material, mud, soils and _______ Nevado Del Ruiz, Colombia, 1985 See Fig. 7.29-30 • Very _____ volcano is topped by large ____ _____ (17,700 ft) • Amero; pop. of 27,000 o At 11 p.m. Nov 10, ________ traveled ____ mi from the mountain top, dropping over __________ ft in elevation. o ___________ buried beneath up to ____ ft of material o ___________ people survived. Why? Mt. Rainier, WA—On Alert See Fig. 7.31 & 7.32  Some say most potentially dangerous  Very unstable due to: 1) great __________ 14,410 ft 2) extensive glacial _______ 3) frequent _______________ 4) active water _________ systems which have ____________ the mountain internally • Mountain may _______ in massive avalanche and/or melted ice may cause floods or lahars, even without eruption • ________ yrs. ago _______ mudflow traveled 75 mi to an area over 100 mi 2 to a depth of 70 ft. Today, over _________ people live in its pathway. Indirect-Famine • Can change ____________, climate and harm ________ and _________ Tambora, Indonesia , 18_______ • ______ violent and explosive eruption of last _____ years • Weeklong eruption spewed out about ____ mi 3 of magma. Plinian explosions blasted up ______ mi for ____ hrs. • Eruption caused ____________ deaths o ____ directly by eruption --on Sumbawa Island, over 10,000 deaths due to pyroclastic flows o ____ from famine or disease, after pyroclastic fallout damaged crops • Affected global climate so that _______ was known as “the year without a _________” Gas _________ Lakes of _________, Africa See Fig 7.35 & 7.36 • Failed ________ setting • Lake _______ was a young crater filled with rainwater; 6,310 ft across by 680 ft deep— collected ______ at base of lake • _______: CO 2 gas river (165 ft thick) rushed towards Cameroon (16 mi) at ___ mph. Spewed out from lake for about ____ hr. • Residents of _____ villages felt fatigue, light-headedness, warmth, and ________ before losing consciousness. • After 6-36 hrs. _______ people awakened at observed ______ killed and _________ dead cattle. • ____________ pipes have been installed into lake

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Lava Flows • _________ big killers! Nyiragongo, Democratic Republic of the Congo (nee Zaire), 2002 • Some _____________ like Nyiragongo of East African Rift Valley have _________ lakes in summit _________ • Low viscosity lava (low silica) flowed down a slope and killed ___ VEIs of Some Killer Eruptions Review Table 7.2 • Does the VEI correlate well with the number of fatalities? (_______ necessarily) • Frequency of different VEI magnitudes is _______ correlation • Bigger eruption, _________ frequent occurrence • Smaller eruption, _______ frequent occurrence • As population _____, more people live in volcano hazard zones • _____ events occur every few weeks • A VEI 5 about every ________ • A VEI 6 about 1 or 2 times per ___________ Volcano Monitoring and Warning • We have had success and failures with prediction Long Valley, CA 1982 • Mammoth located within huge _______ See Fig 7.38 and 7.40 • Very ___________ today ________ lake eruption within 150-250 yrs. • _____________ yrs. ago huge eruption spewed out 150 mi 3 of __________ tuff (_________ Tuff) that covered and area of 580 mi 2 • May 25-26, ________ many earthquakes; ___ greater than 6M and many 4-5M. • Dome had risen ________ in. and magma within ________ mi of surface (some say ________ mile). • Houses prices ______ by ____%. A warning was issued and many became _________ due to a “false alarm” • Since the early _________, _______ from magma is killing ______ Success! Mt Pinatubo, Philippines, 1991 • Nearly _______ million people lived in danger zone • Even though ________ people died, it is estimated that up to _____ _____ have been ________ without forceful warnings. • _____ million spent on monitoring between March and June.

Signs of Impending Eruption • How reliable are these? Seismic Waves • Short period (.02 to .06 s) waves occur as rocks are __________ from upwelling __________ • Long period (.2 to 2 s) waves occur as magma moves up an _________ ___________ • ________ of seismic events can occur in a _______ Ground Deformation • Ground surface _______ and ______ in response to magma movement • This is measured with ____ meters, _____ meters, ______-meters, ___________ Gas Measurements • An increase or decrease can be bad! o Increase—magma moving towards surface and releasing gas due to ________ pressure o Decrease—gas pressure is increasing in sticky magma which could cause a very ___________ event! Mammoth Mountain, California • Increase of CO 2 from magma killed trees o Declining CO 2 levels have relieved worry Galeras Volcano, Colombia • Decrease in gas emissions relieved worry o Volcano was plugged by sticky magma, gas pressure building o Eruption killed _________ volcanologists collecting data in crater Volcano Observatories • In ________ century, _________ had powerful eruptions in Alaska, California, Hawaii, and Washington • At least _____ active or potentially active volcanoes in U.S. • U.S. Geological Survey established Volcano Hazards Program with _________ volcano observatories: – _________, _________, __________, ____________ and ________________ – Each with own websites to report current activity • See Table 7.3 for Volcanic-Alert Levels, USGS Visit this USGS Website on Volcanic Hazards and answer the following questions:

https://volcanoes.usgs.gov/index.html What is the date & time you are looking at the site? How many volcanoes are above the “normal” level? What are the names of those volcanoes?

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