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Montclair EAES 104 - Tsunami Review Questions

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As the tsunami approaches the shoreline, there is friction with the sea floor and it slows the waves down. That then compresses the length of the waves and makes the waves higher. The waves then rush onto shore, and flood the area, and destroy everything in their path.Uplift rates are ~4mm/yr. and eastward transport is ~30mm/yr.Name: Rebecca Gallanter _______Learning Unit 5: Tsunami Review QuestionsThis assignment is designed to assess your understanding of Unit 5 and includes some of the Questions forReview 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 of three 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? A tsunami is a series of waves, often referred to as a “wave train”. They can come in aseries, one after another, and take up to an hour to finish. 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 faults do not cause tsunamis. The main reason is there is no vertical displacement within the fault movement. It only moves back and forth, or side to side.With the other faults, the water rises up, and then when it comes back down, the water that was displaced is what causes the wave for the tsunami.3. How dangerous are tsunami waves in the open ocean? And why?In the open ocean, tsunami waves are low and far apart. They move extremely fast. The waves can move up to several hundreds of kilometers per hour. Both of these factors make them harder to see, and increase their danger levels 4. Which is the more dangerous location for a tsunami, a straight stretch of open coast or a bay? Why?The tsunami would be more dangerous in the open ocean, because there is nothing that can stop the waves. In a bay, they will gradually slow down, but in the open ocean, there is no buffer to the waves.5. What is often the first indication of the arrival of a tsunami at the coast?As the tsunami approaches the shoreline, there is friction with the sea floor and it slows the waves down. That then compresses the length of the waves and makes the waves higher. The waves then rush onto shore, and flood the area, and destroy everything in their path.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?Uplift rates are ~4mm/yr. and eastward transport is ~30mm/yr.7. What are the approximate times between tsunami wave crests?The crests can be anywhere from 10 minutes apart to 35 minutes apart8. Which wave of a major tsunami is likely to be the highest – first, fourth, tenth?The first wave of the tsunami is not likely to be the highest. There is a buildup that occurs the longer that the waves go on, a later wave could come along and be higher than the first one.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)?The initial event was an earthquake under the sea of the Indian Ocean. It happened on December 26 at 7:58:53b. Where, specifically, was that initial event?The earthquake originated in the Indian Ocean, just off the western coast of northern Indonesia. c. What secondary event (the one that killed most of the people) was caused by the initial event noted above?The secondary event was the tsunami devastated the shores of Indonesia, Sri Lanka, Thailand, India, Malaysia, Burma, and Bangladesh with waves up to 100 feet.d. Explain (concisely and in detail) exactly how the initial event was related to the secondary event?When the earthquake happened, somewhere around 745 miles of fault line slipped along the subduction zone. That caused a vertical rise of the seafloor during the earthquake to produce the tsunami. 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.The radiocarbon dating of organics in buried soils along the coast of the Pacific Northwest show researchers that tsunami only have a tendency of reoccurring in that area ranging from 300 to 900 years11. 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?The event occurred on a subduction boundary, between the North American and the Pacific Plate. The type of plate movement that was involved was strike slip movement. b. Explain what tectonic forces led to the ground sinking and later rising.A divergent zone moves the plats apart, and a convergent zone pushes the plates together, so the only thing I can think of is first the plates diverge and the they converge 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)In Lituya Bay, the earthquakes, specifically the one in 1958 that measured as a magnitude 7.5, have been causing rockfalls and landslides. By those things crashing into the water, it causes a wave of over 150m to come crashing down.13. List some of the ways volcanoes can generate tsunami.The ridges that jet out from the top of a shield volcano and become the sites of most eruptions and break the volcano into three very large pieces. By one of these pieces collapsing really quickly into the ocean, it can displace thousands of cubic kilometers of water and generate tsunami hundreds of meters high14. How are tsunami waves in the Atlantic Ocean likely to be generated?Even though they can be generated by an earthquake, it is far more likely that they will be generated by a falling of the side of an oceanic island volcano15.


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Montclair EAES 104 - Tsunami Review Questions

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