ten or more.strike-slip cannot, normal and thrust faults can. Strike-slip faults do not displace water, normal and thrust do displace waterThey are 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.A bay. A bay focuses the wave, forcing the water into a narrower area and causing the wave to rise.less than 20 minutes.10 to 35 minutes. 30 minutes on average.Fourth.Large rockfall (or landslide) triggered by a nearby earthquakeName: _______________________Learning Unit 5: Tsunami Review QuestionsThis assignment is designed to assess your understanding of Unit 5 and includes some of the Questions for Review at the end of Chapter 5 from your text plus a few additional questions. Each question can be answered in one to two sentences. Please limit yourself to a maximum ofthree sentences. Access the assignment, complete it with ANSWERS IN A DIFFERENT COLOR FONT as a separate file, and send it back for evaluation and grading through the assignment tab by or before the due date. 1. How many tsunami waves are generated when an abrupt disturbance, such as an earthquake, vertically displaces the water column? ten or more.2. Of the three main types of fault movements—strike-slip faults, normal faults, and reverse (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. How dangerous are tsunami waves in the open ocean? And why?They are 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.4. Which is the more dangerous location for a tsunami, a straight stretch of open coast or a bay? Why?A bay. A bay focuses the wave, forcing the water into a narrower area and causing the wave to rise.5. What is often the first indication of the arrival of a tsunami at the coast?A rapid drop in sea level.6. 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 minutes.7. What are the approximate times between tsunami wave crests?10 to 35 minutes. 30 minutes on average.8. Which wave of a major tsunami is likely to be the highest – first, fourth, tenth?Fourth.9. In December, 2004, a pair of closely related natural disasters killed tens of thousands of people. (Case in Point: Lack of Warning and Education Costs Lives, Sumatra Tsunami, 2004)a. What was the initial event (not the one that killed most of the people)? a major earthquakeb. Where, specifically, was that initial event? off the southwest coast of Sumatrac. What secondary event (the one that killed most of the people) was caused by the initial event noted above? tsunamid. Explain (concisely and in detail) exactly how the initial event was related to the secondary event? the earthquake caused the tsunami when fault movement on the ocean floor suddenly pushed up a large mass of water.10.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.A sequence of peat, sand, and mud are a geologic record of tsunami. Radiocarbon dating oforganics in buried soils along the coast of the Pacific Northwest indicate tsunami with recurrence intervals ranging from 300 to 900 years. Radiocarbon dating places the last of those events around 1700. The subduction zone has been locked ever since. Convergence along the subduction zone causes bulging of the N.A. plate off the coasts of Oregon, Washington at a rate of ~4mm/yr. with an eastward transport of ~30mm/yr. indicating that strain energy is building along the subduction zone and the next major earthquake could occur at any time.11.On low-lying coastal flats near Anchorage, Alaska, the foundations of buildings dropped below sea level during the giant 1964 earthquake. Decades later, their foundations are again above sea level. (Case in Point: Subduction Zone Earthquake Generates a Major Tsunami)a. What type of tectonic boundary caused the earthquake, and what plate motions are involved?Subduction zone boundary, the Pacific Ocean floor is descending under the continental margin (ocean-continent convergent boundary)b. Explain what tectonic forces led to the ground sinking and later rising.While the subduction zone fault was locked, descent of the ocean floor pulled down the edge of the continental margin, causing it to slowly buckle up. Release of the boundary during the earthquake permitted the ground to drop suddenly and the sea move in. Decades later the edge of the continent is again rising since the subduction zone fault isagain locked.12.What type of event has repeatedly generated high tsunami waves in Lituya Bay of southeastern Alaska? Be specific. (Case in Point: Immense Local Tsunami from a Landslide, Lituya Bay, Alaska, 1958)Large rockfall (or landslide) triggered by a nearby earthquake13.List some of the ways volcanoes can generate tsunami.Volcanic processes displace large volumes of water; water is driven upward or outward by fast-moving flows of hot volcanic ash or submarine volcanic explosions into a large body of water; volcanoes can also collapse in a giant landslide and spill volcanic material into the ocean.14.How are tsunami waves in the Atlantic Ocean likely to be generated?By collapse of the flank of an oceanic volcano like the Canary Islands.15.Why are even good swimmers often killed by tsunami waves?Impact of debris carried in the waves or abrasion by being dragged along the bottom at high rates of
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