Name: ______Caleigh Kehoe_____ Learning Unit 5: Tsunami Review Ques<ons This assignment is designed to assess your understanding of Unit 5 and includes some of the Ques<ons for Review at the end of Chapter 5 from your text plus a few addi<onal ques<ons. Each ques<on 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 evalua<on 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, ver<cally displaces the water column? There are lots of waves generated since a tsunami us known as a wave train; this means that the waves come one aVer the other. The waves keep coming for up to an hour aVer the earthquake. 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? A strike-slip fault cannot cause a tsunami because the fault movement is only back and forth. Due to the fact it is not up and down, there is no ver<cal displacement of the water like there is with normal and reverse faults. 3. How dangerous are tsunami waves in the open ocean? And why? Tsunami waves in the open ocean are not dangerous due to the depth of the ocean, the waves are low. The slopes of the waves are gentle and they are far apart from one another so many people might not expect to no<ce them. 4. Which is the more dangerous loca<on for a tsunami, a straight stretch of open coast or a bay? Why? The more dangerous loca<on for tsunami is a bay because it will concentrate the energy of the tsunami causing amplifying effects of the tsunami. 5. What is oVen the first indica<on of the arrival of a tsunami at the coast? The first indica<on of the arrival of a tsunami at the coast is a rapid drop in sea level. 6. For a subduc<on-zone earthquake off the coast of Oregon or Washington, how long would it take for a tsunami wave to first reach the coast?For a subduc<on-zone earthquake off the coast of Oregon or Washington, it would take 15 to 20 minutes for the tsunami wave to reach the coast. 7. What are the approximate <mes between tsunami wave crests? The approximate <mes between tsunami wave crests is 10-30 minutes. 8. Which wave of a major tsunami is likely to be the highest – first, fourth, tenth? The fourth wave of a major tsunami will most likely be the highest. 9. In December, 2004, a pair of closely related natural disasters killed tens of thousands of people. (Case in Point: Lack of Warning and Educa<on Costs Lives, Sumatra Tsunami, 2004) a. What was the ini<al event (not the one that killed most of the people)? The ini<al event was an earthquake in a subduc<on zone caused by a thrust-fault movement. b. Where, specifically, was that ini<al event? The ini<al event was in Asia, specifically off the southwest coast of Sumatra in Indonesia. c. What secondary event (the one that killed most of the people) was caused by the ini<al event noted above? A tsunami was the secondary event which killed a lot of people. d. Explain (concisely and in detail) exactly how the ini<al event was related to the secondary event? The ini<al event was related to the secondary event because there was a thrust fault movement in the subduc<on zone, a large amount of water was pushed up and ver<cally displaced; this causing the tsunami. 10.There have not been any very large earthquakes on the subduc<on zone of the coast of Washington and Oregon in hundreds of years. Explain why not and what are the implica<ons based on records of past events. The last earthquake on the subduc<on zone of the coast of Washington and Oregon because the plates are locked. It has been 300 years since the last earthquake causing an intense fric<on and when there is one it will be massive. 11.On low-lying coastal flats near Anchorage, Alaska, the founda<ons of buildings dropped below sea level during the giant 1964 earthquake. Decades later, their founda<ons are again above sea level. (Case in Point: Subduc<on Zone Earthquake Generates a Major Tsunami) a. What type of tectonic boundary caused the earthquake, and what plate mo<ons are involved? A subduc<on zone boundary involving the plates of the Pacific Ocean floor movingunder the con<nental margin. b. Explain what tecon<c forces led to the ground sinking and later rising. The subduc<on zone fault was locked, but over<me the ocean floor descended and pulled with its the con<nental margin. This caused it to slowly buckle and release the boundary, meaning the lock; this made the seafloor drop suddenly during the earthquake. Since the subduc<on zone fault is again locked, the edge of Alaska is rising. 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) Due to huge rock falls and landslides caused by earthquakes; in 1958, it was a strike-slip flat caused the high tsunami waves. 13.List some of the ways volcanoes can generate tsunami. The underwater or above water explosions and shockwaves of volcanoes can generate a tsunami, due to the displacement of water. Landslides from the erup<on can move into the water quickly causing the displacement that generates a tsunami. The volcano can collapse into itself causing a caldera, which will also displace a large amount of water. 14.How are tsunami waves in the Atlan<c Ocean likely to be generated? Tsunami waves in the Atlan<c Ocean likely to be generated by the collapse of the flank of an oceanic island volcano in the Canary Islands. 15.Why are even good swimmers oVen killed by tsunami waves? Tsunami waves carry a large amount of debris with them, which can hit the good swimmers and kill
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