CHAPTER 5TSUNAMI: THE GREAT WAVECHAPTER 5: End of Chapter Answers* sub-sea earthquakes, landslides into a body of water, volcano-flank collapse into a water body, sub-sea volcanic eruptions, asteroid impact into an ocean2. Of the three main types of fault movements—strike-slip faults, normal faults, and thrust faults—which can and which cannot cause tsunami? Why?* strike-slip cannot, normal and thrust faults can* strike-slip faults do not displace water, normal and thrust do displace water3. About how high are the largest earthquake-caused tsunami waves in the open ocean?* about 15 meters* wave height increases. Since more water of each wave is forced into a narrower area the height must rise to accommodate the volume of water.5. How many tsunami waves are generated by one earthquake?* ten or more6. How fast do tsunami waves tend to move in the deep ocean?* about 760 km/hour (or 475 mi/hour)* They slow down because the waves drag on, and are held back by, the shallower bottom.8. Why is even the side of an island away from the source earthquake not safe from a tsunami?* because the waves can refract around the coast of an island to strike the opposite side.9. For a subduction-zone earthquake off the coast of Oregon or Washington, how long would it take for a tsunami wave to first reach the coast* less than 20 minutes10. Because the Atlantic coast of North America experiences few large earthquakes, what specific other event could generate a large tsunami wave that could cause catastrophic damage there?* flank collapse of a volcano in the Canary Islands or landslide of a large section of the continental shelf11. What specific evidence is there for tsunami events having struck bays on the coasts of Washington and Oregon?* flattened and drowned forests, massive sand sheets that cover coastal peat soils.12. What is a seiche? (be specific)* a wave that sloshes back and forth from end to end of an enclosed body of water.CHAPTER 5: Short answer questions:1. In December, 2004, a pair of closely related natural disasters killed tens of thousands of people?2. Along the San Andreas Fault in California, how many magnitude 7 earthquakes would it take to relieve the same stress in the rocks as one magnitude 8 earthquake?* about 323. Why are tsunami waves in the open ocean limited in height?*15 meters is about the largest offset on a fault on the ocean floor so that is also the largest wave height generated.4. About how high are the largest earthquake-caused tsunami waves in bays?* about 30 meters6. Which is the more dangerous location for a tsunami hazard, a straight stretch of open coast, a rocky point, or a bay? [or what is the most hazardous area along a coast?]* a baya. Why?* a bay focuses the wave, forcing the water into a narrower area and causing the wave to rise.7. What are the approximate tsunami-wave velocities over the continental shelf or near-shore?* about 100 km/hour8. What are the approximate wavelengths of tsunami waves?* 200 km9. What are the approximate times between tsunami wave crests?* 10 to 35 minutes11. What type of event has repeatedly generated high tsunami waves in coastal fjords of southeastern Alaska? Be specific.* large rockfall (or landslide) triggered by a nearby earthquake12. Why do ships in the open ocean not notice passage of a tsunami wave?* the time between wave crests is 10 to 30 minutes and the wave rises and falls less than 15 meters in that time.13. How dangerous are tsunami in the open ocean and why?not dangerous at all. The wave height is so much smaller than the wave length, and the time between wave crests is so long, that you would not even notice them.14. Which wave of a major tsunami is likely to be the highest? 1st, 4th, 10th, 20th?* 4th15. At what depth in the ocean do tsunami waves drag on bottom?16. How are tsunami waves in the Atlantic Ocean likely to be generated?21. About how many years are there between giant tsunami from the Cascadia subduction zone that inundate the west coast of North America?22. When was the last giant tsunami event to affect the west coast of Washington and Oregon?23. There have not been any very large earthquakes on the subduction zone of the coast of Washington and Oregon in hundreds of years. Explain why not and what are the implications based on records of past events.* subduction zone is locked* last major earthquake was in 1700.* giant earthquakes every few hundred years* next major earthquake could come any timeCHAPTER 5: - Multiple choice questionsa. volcano-flank collapse & sudden degassing of the mantle from a mid-oceanic ridgeb. sudden changes in ocean-floor lithosphere velocity & major rockfall into the oceanc. asteroid impact into the ocean & collapse of a mid-oceanic ridge.d. subduction-zone earthquakes and transform-fault earthquakese. * subduction-zone earthquakes & landslide into the ocean5. The following submarine faults cannot cause tsunami waves.a. * strike-slip faultsb. normal faultsc. subduction-zone faultsd. thrust faultse. breakaway faults of major landslides6. The largest earthquake-caused tsunami waves in the open ocean are about:a. * about 15 meters highb. about 1 meter highc. about 50 meters highd. about 300 meters highe. about 1 kilometer higha. * rises because more water of each wave is forced into less spaceb. rises primarily because the bay narrowsc. rises because of thermal expansion in the warm water of the bayd. drops because the wave must spread out and slow as it approaches the shoree. drops because as the wave breaks it rushes ahead as a fast-moving swash8. The number of tsunami waves generated by one earthquake is generally:a. oneb. * 10 or 12c. about 50d. about 100-120e. 1000 or more.9. The speed of tsunami waves in the deep ocean is generally about:a. 7-8 km/hourb. 70-80 km/hourc. * 700-800 km/hourd. the speed of an Olympic sprintere. the speed of light.a. slow down because they don’t want to hit the coast too fastb. slow down because they finally begin to feel bottomc. * slow down because they drag more on the shallower bottom than in the deep oceand. speed up because the shallowing water forces the leading edge to squirt out aheade. speed up because the wave launches forward as it breaks.11. For a subduction-zone earthquake off the coast of Oregon or Washington, how long would it take for a tsunami wave to first reach the coast?a. about 20 secondsb. about 2 minutesc. * less than 20 minutesd. about 2 hourse. about 20 hours.12. Although the Atlantic coast of North America