* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download chapter 6 - Geophile.net
Itcha Range wikipedia , lookup
Mount Garibaldi wikipedia , lookup
Craters of the Moon National Monument and Preserve wikipedia , lookup
Llullaillaco wikipedia , lookup
Large igneous province wikipedia , lookup
Mount Meager massif wikipedia , lookup
Level Mountain wikipedia , lookup
Mount Edziza volcanic complex wikipedia , lookup
Cerro Blanco (volcano) wikipedia , lookup
Mount Pinatubo wikipedia , lookup
Olympus Mons wikipedia , lookup
Shield volcano wikipedia , lookup
Wells Gray-Clearwater volcanic field wikipedia , lookup
Lascar (volcano) wikipedia , lookup
Cascade Volcanoes wikipedia , lookup
Volcanology of Io wikipedia , lookup
Nevado del Ruiz wikipedia , lookup
Mount Pleasant Caldera wikipedia , lookup
Mount St. Helens wikipedia , lookup
Silverthrone Caldera wikipedia , lookup
Mount Vesuvius wikipedia , lookup
Cerro Azul (Chile volcano) wikipedia , lookup
Chapter 5: Tsunami CHAPTER 6 VOLCANOES: MATERIALS, HAZARDS, AND ERUPTIVE MECHANISMS Correct answers are indicated by an asterisk, both in short answer and multiple choice questions. True or False questions can be easily prepared from multiple choice questions Web Sites: http://eos.higp.hawaii.edu/eos/ http://hvo.wr.usgs.gov/ http://interactive2.usgs.gov/learningweb/explorer/topic_hazards_volcanoes.asp http://lvo.wr.usgs.gov/ http://volcano.und.nodak.edu/ http://volcanoes.usgs.gov http://volcanoes.usgs.gov/educators.html http://vulcan.wr.usgs.gov/home.html http://www.avo.alaska.edu/ http://www.dartmouth.edu/~volcano/ http://www.geo.mtu.edu/volcanoes/ http://www.ig.utexas.edu/research/projects/lips/lips.htm http://www.soest.hawaii.edu/GG/hcv.html http://www.volcano.si.edu/ http://www.vsc.washington.edu Videos: Video: NOVA - ?Volcano! Video: NOVA - In the path of a killer volcano Video: NOVA - ?Return to Mt. St. Helens Video: National Geographic - In the Shadow of Vesuvius, 1989 (60 min.) Exc. footage of 1944 eruption of Vesuvius and reconstruction of the events that destroyed Pompeii and Herculaneum. Video: USGS library spec. collections, MS 955, 345 Middlefield Rd., Menlo Park, CA 94025 (415)3295009. Video: BBC Horizon Series, 1987, "The Magma Chamber," (50 min.) Osbour Court, Olney Buckinghamshire, MK 46 4AG United Kingdom. Phone 0234-711198 or 713390. [how studies of magma at depth aid in the prediction of eruptions] Video: Gould Media, Inc., Mount Vernon: NY Volcanoes of the United States Video: Gould Media, Inc., Mount Vernon, NY Mount St. Helens: What Geologists learned Video: Annenberg/CPB Collection: Earth revealed #13: Volcanism; P.O. Box 1922, Santa Barbara, CA Video: Geoscience Resources: Eruptive phenomena of Kilauea’s East Zone. Video: Smithsonian Institution; NHB-119, Washington, DC 20560, Washington, D.C.: Inside Hawaiian volcanoes Video: International Association of Volcanology and Chemistry of the Earth’s Interior: Reducing Volcanic Risk. Nature: Catastrophe on Sakhalin References: Carey, S., H. Sigurdsson, and C. Mandeville, 1992, Fire and water at Krakatau: Earth, v. 1, no. 2. (1983 eruption) Carey, S., H. Sigurdsson, C. Mandeville, and S. Bronto, 2000, Volcanic hazards from pyroclastic flow Chapter 5: Tsunami discharge into the sea: Examples from the 1883 eruption of Krakatau, Indonesia: p. 1-14, in McCoy, F.W. and G. Heiken, editors, Volcanic hazards and disasters in human antiquity: Geological Society of America special Paper 345. Crandell, D.R. and D.R. Nichols, 1989?, Volcanic hazards at Mt. Shasta: U.S. Geol. Survey . Decker, R. and B. Decker, 1989, Volcanoes: W.H. Freeman and Co., New York, 285 p. Ewert, J.W. and D.A. Swanson, 1992, Monitoring volcanoes - Techniques and strategies used by the staff of the Cascades Volcano Observatory, 1980-1990: U.S. Geol. Survey Bull. 1966, 223 p. Fisher, R.V., G. Heiken, and J.B. Hulen, 1997, Volcanoes, Crucibles of Change: Princeton University Press, Princeton, N.J., 317 p. Heliker, C. 1993, Volcanic and seismic hazards on the Island of Hawaii: Bishop Museum Press, Honolulu, 52 p. Heliker, C., D.A. Swanson, and T.J. Takahashi, 2003, The Pu’u O’o’ Kupaianaha eruption of Kilauea Volcano, Hawai’i: The first 20 years: U.S. Geological Survey Professional Paper 1676, 206 p. Jäger, S. and G.F. Wieczorek, 2000, Landslide susceptibility in the Tully Valley area, Finger Lakes Region, New York: U.S.G.S. Open-file report 94-615, 14 p. on-line version Lipman, P.W. and D.R. Mullineaux, editors, 1981, The 1980 eruptions of Mount St. Helens, Washington: U.S. Geological Survey Professional Paper 1250, 844 p. McGuire, W.J., A.P. Jones, and J. Neuberg, editors, 1996, Volcano instability on the earth and other planets: Geological Society Special Publication no. 110. Rhodes, J.M. and J.P. Lockwood, editors, 1995, Mauna Loa Revealed: Structure, composition, history, and hazards: American Geophysical Union, Geophysical Monograph, v. 92, 348 p. Scarpa, R. and R.I. Tilling, eds., 1996, Monitoring and mitigation of volcano hazards: Springer-Verlag, N.Y., 862 p. Scott, K.M., J.W. Vallance, and P.T. Pringle, 1995, Sedimentology, behavior, and hazards of debris flows at Mount Rainier, Washington: U.S. Geol. Survey Prof. Paper 1547. Sigurdsson, H. 1990, Assessment of the atmospheric impact of volcanic eruptions, in Global catastrophes in Earth History, An interdisciplinary conference on impacts, volcanism, and mass mortality, V.L. Sharpton and P.D. Ward, editors: Geological Society of America Special Paper 247. Tilling, R.I., 1989, Volcanic hazards - International Geological Congress, 28th, Short Course in Geology: Vol. 1, American Geophysical Union, Washington, DC. CHAPTER 6 - End of Chapter Answers 1. What factors influence the violence or style of an eruption? * amount of water (more water, more violent eruptions) * viscosity of the magma (higher viscosity, more violent eruptions) (or composition of magma - e.g. rhyolite more violent than basalt) 2. What properties of basalt magma control its eruptive behavior? * low water content a. low viscosity 3. What properties of rhyolite magma control its eruptive behavior? * high water content * high viscosity 4. What drives an explosive eruption? * steam 5. How does pahoehoe lava differ from aa lava? Chapter 5: Tsunami * pahoehoe is ropy-looking; aa is clinkery 6. How fast do red hot basalt flows typically move? * less than 1 meter per second (about that of a brisk walk) 7. How much ash on a roof would generally cause it to collapse? * about 20 cm 8. Which is more dangerous to a person—an ash fall or an ash flow? Why? * an ash flow. Falling ash is cool or cold. An ash flow would incinerate the person; it is extremely hot and suffocating 9. Why is erupting volcanic ash dangerous to jet aircraft flying at an altitude of 8 to 10 kilometers (30,000 feet)? * The ash gets into the engine and the engine heat melts it. It coats the inside of the engine and can stop it, causing the plane to crash. 10. What causes a big bulge to slowly grow on the flank of an active Cascades volcano? * It grows because rising magma is pushing it up 11. If you visit Mount St. Helens, Washington, you will see thousands of trees lying on the ground, all parallel to one another. Explain how they got that way. * The intense lateral blast at the beginning of the eruption blew them all down with their tops pointing away from the site of the blast. 12. If an ash flow approaches you from across a kilometer-wide lake, are you likely to be safe or not? Explain why. * Not safe. Ash flows can cross much wider bodies of water. 13. What characteristics of an old ash-fall tuff will permit you to distinguish it from an old ash-flow tuff? * an ash-flow tuff is not thinly layered and pumice fragments in it generally become coarser upward. Its lower part is commonly cross-bedded. It forms thicker deposits in valleys and its lower part may show lenses of black obsidian. 14. Which of the hazards of erupting volcanoes kill more people than anything else? Why are they so dangerous? * mudflows. They flow down valleys where people live. They flow at high speed and are as dense as wet concrete. 15. What can happen to heat, pressure, and water content to melt rock and create magma? * add heat, decrease pressure (dry), or add water to cause melting. Chapter 6 - Short answer questions Chapter 5: Tsunami 1. About how fast can ash flows travel? * more than 160 km per hour; up to 200 km per hour 2. What are the main distinctions between basalt and rhyolite? Complete the following table: basalt rhyolite b. color: *black or dark white or pale colors c. silica percent: *50 % 70 % d. most abundant gas: *carbon dioxide water (or steam) e. viscosity (relative): *low high f. how explosive (relative): *not very very 3. A basalt magma typically erupts in what form? * lava flows 4. A rhyolite magma typically erupts in what form? * ash (ash fall or ash flow) 5. What are the two most-abundant gases in magmas? * Water vapor and carbon dioxide 6. Which common volcanic gases are poisonous? Name two. * carbon dioxide in high concentrations * sulfur oxides (or hydrogen sulfide) 7. Which of those two gases is heavier than air, collects in low areas, and can asphyxiate people or animals if it is in high concentrations? * carbon dioxide 8. What two main influences on a water-bearing basaltic magma can cause water to separate from a magma to drive an eruption? * decrease in pressure * crystallization 9. What two main factors dictate that an erupting magma will be explosive? * high water content, high viscosity 10. If the bulge grows steep enough it may collapse. Explain how this can trigger an explosive eruption? * Collapse of the bulge decreases pressure on gases dissolved in the magma. That permits them to separate from the magma, expand rapidly, and drive the explosive Chapter 5: Tsunami eruption. 11. Sketch a simple diagram to show controls over the hazard distance from a volcano for an ash flow. Label the diagram completely. * gas thrust zone sloping energy line tops this hill stops at this hill 12. If an ash flow approaches you from the opposite side of a large hill, are you likely to be safe or not? Explain why. * If the hill is high enough and far enough from the volcano you may be safe because the flow tends to flow down valleys. If the hill is not so high or is closer to the volcano you are not safe since their momentum can carry them over the top. 13. An extremely large volcano with very gentle slopes is likely to be what kind of volcano and is likely made of what kind of rock? Be specific. * a shield volcano of basalt lava flows 14. A large, steep-sided volcano is it likely made of what composition of rock? In what form was the rock erupted? What type of volcano is it? * andesite lava flows and ash; a stratovolcano 15. A small, steep, smooth-sided volcano is likely to be what type of volcano? What is it likely made of? * basalt fragments; a cinder cone. 16. Why do landslides sometimes trigger explosive eruptions? * Removal of load by landsliding, decreases pressure on gases in the magma and permit Chapter 5: Tsunami them to expand explosively. 17. How does lava differ from magma? * Lava is magma that erupts onto the Earth’s surface. 18. Why might a landslide trigger a volcanic eruption? * it would remove load from the magma chamber to permit gas to bubble out of a magma and explode. 19. What danger signs might indicate that a volcano may be preparing to erupt? * numerous small earthquakes, harmonic tremors, steam blasts, small ash eruptions, opening fractures, growth of a bulge, burning methane. Chapter 6 - Multiple choice questions: 1. What two main factors result in more violent eruptions? a. not too much water and low enough viscosity b. * more water and higher viscosity of the magma c. higher viscosity and narrow enough vent d. strong rocks around the vent and more water e. a large enough volcano with low-viscosity magma. 2. What properties of basalt magma control its eruptive behavior? a. low water and large magma volume b. high water and low magma volume. c. * low water content and low viscosity d. low water and high viscosity e. high water and low viscosity 3. What properties of rhyolite magma control its eruptive behavior? a. * high water content and high viscosity b. low water and large magma volume c. high water and low magma volume. d. low water content and low viscosity e. low water and high viscosity 4. How does pahoehoe lava differ from aa lava? a. pahoehoe is full of gas holes and aa is solid lava. b. pahoehoe has a ragged top, aa is smooth on top c. * pahoehoe is ropy-looking; aa is clinkery d. pahoehoe is rhyolite and aa is basalt e. pahoehoe is basalt and aa is andesite Chapter 5: Tsunami 5. How fast do red-hot basalt flows typically move? a. about 5 meters per hour. b. about 5 centimeters per minute c. * less than 1 meter per second d. 10 meters per second e. 10 kilometers per minute 6. What is the smallest amount of volcanic ash on a roof would commonly cause it to collapse? a. no amount of ash would cause collapse; it is too light to be a problem. b. more than about 3 cm c. * more than about 20 cm d. more than 2 meters e. more than 20 meters 7. Why is erupting volcanic ash dangerous to jet aircraft flying at an altitude of 8 to 10 kilometers (30,000 feet)? a. ash coats the surface of the wings making the plane too heavy to fly b. ash covers the windshield of the plane so the pilots can’t see where they are going c. pieces of ash are rising so fast that they shoot down the plane d. *ash gets into the engines, which melt the ash causing the engines to stop e. ash can penetrate the aluminum body of the fast-moving plane causing decompression of the plane and deaths of all on board. 8. What causes a big bulge to slowly grow on the flank of an active Cascades volcano? it grows because: a. thick lava flows pile up around the vent b. a huge gas bubble released from the magma is inflating it c. the magma reacts with snow on the volcano, causing magma inflation d. the hot magma melts older ash, causing it to expand. e. * rising magma is pushing it up 9. Following the May 1980 eruption of Mount St. Helens, Washington, thousands of trees lay on the ground, all parallel to one another, because:. a. * a lateral blast at the beginning of the eruption blew them all down b. a big earthquake at the beginning of the eruption shook them down c. huge mudflows racing down slope flattened them d. a giant landslide from the volcano toppled them e. thermal winds during the eruption toppled them. 10. If an ash flow approaches you from across a kilometer-wide lake, are you likely to be safe or not? Explain why. Chapter 5: Tsunami a. b. Safe; hot ash slows would chill and stop as soon as they hit cold water Safe; ash flows move along the ground; they would continue harmlessly underwater c. Safe; hot ash flows would boil the water and that would stop them d. Not safe because a fast-moving ash flow would cause a deadly tsunami wave. e. * Not safe. Ash flows can cross much wider bodies of water 11. Which of the following would you not find in an old ash-flow deposit? a. pumice fragments in it become larger upward. b. It is thicker in the valley bottom than on adjacent ridges c. streaks of black obsidian near the base of the deposit. d. * thin layers of ash e. charred logs 12. Which of the hazards of volcanoes kill more people than anything else? a. lava flows b. ash flows c. ash falls d. landslides. e. * mudflows 13. If a mudflow is heading down valley toward you, the best way to survive is: a. * climb the valley side to be above the flow b. run down valley – fast! c. if there is a house in the valley, nearby, get inside so the flow will go around you d. climb the nearest tree e. jump onto a tree floating in the mudflow and ride it down valley until it slows down. 14. If a gigantic flow of flood basalt magma were to erupt, why might that cause an increase in global warming? a. The high temperature of a giant basalt lava flow would heat up the atmosphere b. Basalt magma contains steam at such a high temperature that the steam would heat the atmosphere c. The high temperature of the basalt lava would start widespread fires that would heat the atmosphere d. Radiant heat from the red-hot basalt would heat the molecules in the atmosphere. e. * A huge amount of carbon dioxide released from the basalt magma would contribute to global warming 15. About how fast can ash flows travel? Chapter 5: Tsunami a. b. c. d. e. up to 1 to 2 km per hour up to about 16 km per hour generally slower than you can run * more than 160 km per hour; up to 200 km per hour more than 1600 km per hour. 16. A basalt magma typically erupts in what form? a. pale ash flows b. pale air-fall ash c. giant Plinian eruptions that rise 50 km into the atmosphere d. violent steam-rich surge blasts e. * lava flows 17. A rhyolite magma typically erupts in what form? a. thin, fast-moving lava flows b. thick, fast-moving lava flows c. thin, slow-moving ash flows d. * fine ash e. rhyolite magma never erupts. 18. What are the two most abundant gases in magmas? a. water vapor and oxygen b. * Water vapor and carbon dioxide c. hydrogen and methane d. methane and helium e. carbon dioxide and oxygen. 19. Which of the two main volcanic gases is heavier than air, collects in low areas, and can asphyxiate people or animals if it is in high concentrations? a. water vapor b. hydrogen c. * carbon dioxide d. ethane e. helium. 20. What can cause water to separate from a water-bearing basaltic magma to drive an eruption? a. injection, into the basalt magma chamber, of dry rhyolite magma from below b. * decrease in pressure as the magma rises c. water streaming up into the magma chamber from the Earth’s mantle d. once water gets into a basalt magma it can’t separate e. basalt magmas only erupt as lava flows; water is irrelevant. 21.If the bulge grows steep enough it may collapse. Explain how this can trigger an explosive eruption? a. That removes the cover over the magma so it can escape Chapter 5: Tsunami b. c. That slices through some of the gas bubbles, making them pop That doesn’t trigger an explosive eruption; it does, however create a devastating landslide d. The friction of the landslide heats that part of the magma so the dissolved water flashed into steam. e. * That decreases pressure on gases dissolved in the magma, permitting them to expand 22.If an ash flow approaches you from the opposite side of a large hill, are you likely to be safe or not? a. being behind a hill you are fine; ash flows go down valleys b. safe because the ash flow would stop at the hill or go around the sides of it c. safe because you can duck and it will go over top of you d. * not if you are close to the volcano; fast-moving ash flows can go over nearby hills e. not safe because even well away from the volcano when the ash flow reaches the top of a hill it picks up speed going down the far side and that takes it to the top of the next hill, and so on. 23.Which of the following locations five kilometers from the crater of a volcano, if any, likely would be safe from a large ash flow? Explain why or why not. a. far side of a steep-sided, 100-meter-high hill b. far side of a five-kilometer-wide lake c. behind a large tree with an 80-centimeter-diameter (2 ½ feet) trunk d. * None of them: ash flows can flow over large hills ash flows can cross large expanses of water ash flows can fell very large trees 24.In contrast to an old ash-flow deposit, an old ash-fall tuff do not include which of the following? a. thin layers b. layers become coarser-grained towards the base c. the ash evenly coats hills and valleys d. the ash is never welded to black obsidian e. * big pieces of pumice float to the top of a layer. 25.If you see an extremely large volcano with very gentle slopes, what kind of a volcano is it and what rock is it likely made of? a. a stratovolcano made of andesite b. a stratovolcano made of basalt lava flows c. a stratovolcano made of rhyolite lava flows. d. * a shield volcano of basalt lava flows Chapter 5: Tsunami e. a cinder cone made of basalt 26.If you see in the distance, a large, steep-sided volcano, what type of volcano is it and what rock composition? a. a stratovolcano of andesite lava flows and ash b. a stratovolcano of rhyolite lava flows c. a stratovolcano of basalt lava flows d. a shield volcano of andesite ash e. a shield volcano of rhyolite lava flows 27.If you see in the distance, a small, steep, smooth-sided volcano what type of volcano is it and what is it likely made of? a. a stratovolcano of andesite lava flows and ash b. a stratovolcano of rhyolite lava flows c. a stratovolcano of basalt lava flows d. a shield volcano of andesite ash e. * a cinder cone of basalt fragment. 28.Why do shield volcanoes have very gently sloping sides? a. Their andesite composition produces huge ash flows that spread over a large area b. Their andesite and rhyolite have low viscosity because of their water content, and spread over a low slope c. * Their basalt flows have low viscosity so the lava solidifies on a gentle slops d. Their basalt ash spreads out widely in the strong winds over the open ocean e. Their basalt magmas blow out violently from all of their pent up steam 29.Which of the following is not a sign suggesting that a stratovolcano may be getting ready to erupt? a. numerous small earthquakes, b. harmonic tremors, c. growth of a bulge, d. burning methane e. * a large mudflow a year after a previous explosive eruption. 30.Highly explosive magmas are controlled by which of the following? a. high magnesium content and high water b. * high silica content and high water c. low silica content and high water d. high silica content and low water e. high iron content and low water 31.Magma that is forcefully ejected into the atmosphere as particles is: a. * pyroclastic Chapter 5: Tsunami b. c. d. lava pahoehoe plutonic 32.Eruptions dominated by basalt compositions are found: a. along convergent margins involving oceanic and continental crust b. * along divergent boundaries at mid-oceanic ridges c. over continental hotspots d. between plates along transform boundaries