Exam 2 Study Guide

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EAPS 106, Geosciences in the Cinema Exam 2 Study Guide Know the following: Unit 4 - Tsunamis 1. Why it is not sufficient to be a good swimmer to survive a tsunami. People are often crushed by debris when they are caught in tsunamis because of how powerful they are. 2. The process associated with subduction zone earthquakes that causes a tsunami to be generated. Elastic rebound of the overriding plate causes uplift of the seafloor, which causes a mountain of water to form that then falls away in both directions to generate tsunamis in both directions 3. The direction an island above a subducting plate moves between earthquakes. Between earthquakes, an island above a subducting plate sinks. During an earthquake, the island rises 4. The magnitude a subduction zone earthquake has to be to generate a large tsunami. In order to generate a large tsunami, an earthquake must be at least M9 5. That tsunami waves traveling through the deep ocean are influenced by seafloor topography. Tsunami waves are influenced by seafloor topography as they travel, which can influence how the wave spreads. This is because a subduction zone tsunami is initiated on the seafloor 6. That slip on an underwater strike-slip faults cannot cause a significant tsunami. Strike-slip faults will not cause a change in the height of the seafloor; thus they do not displace water and will not generate a tsunami 7. How tsunami waves differ from large wind-blown waves. Tsunami waves and wind-blown waves can have similar heights, but tsunami waves carry a much larger volume of water and have a longer wavelength (wind-blown waves are only on the surface, while tsunami waves go all the way to the seafloor) 8. What happens to a tsunami wave speed and height as it approaches the shore. As tsunami waves approach the shore, they slow down, causing the wavelength to decrease and the wave height to increase to 10s of feet (in deep water the waves rarely have heights over 1m) 9. What happens to the distance between tsunami wave crests as they approach the shore. As tsunami waves approach the shore, the wavelength of the waves decreases. 10. What “tsunami” translates to in Japanese. Tsunami is Japanese for harbor wave because fishermen out at sea would not be able to tell a tsunami was coming and then come home to a destroyed town 11. What happens to a boat in the middle of the ocean when a tsunami wave passes underneath. Boats in the middle of the ocean would rise less than 1m of a period of 10s of seconds if a tsunami wave passed underneath 12. When a wave moving toward shore typically breaks. A tsunami wave moving towards shore typically breaks when the height of the wave is roughly equal to the depth of the water 13. Why inlets (natural harbors) are particularly dangerous places when a tsunami hits. Inlets are dangerous because the incoming water becomes trapped and piles up, causing wave heights to increase even more 14. That an earthquake on the San Andreas Fault cannot cause a tsunami. The San Andreas Fault cannot create a tsunami because it is a strike-slip fault 15. That tsunami waves can be extremely deadly even many miles inland from the shore. This is true, tsunami waves can carry great amounts of debris, which is very dangerous 1
16. The approximate number of people killed by tsunamis in the past 1000 years. Several hundred thousand 17. That the 2011 Japan tsunami was not unprecedented in Japan’s history. Japan should have anticipated the 2011 tsunami because they have has 3 10+ meter tsunamis in the past 400 years 18. What a Japanese tsunami stone is. A stone that is placed where the tsunami waters reached, warning people not to build below them 19. How we know that the northwest coast of the U.S. has experienced large tsunamis. Buried sand deposits along the coast of the Pacific Northwest 20. The time it takes from earthquake to a tsunami reaching the nearest coastline. After a significant earthquake, the tsunami will hit roughly 20-40 minutes later 21. Why sea level drops dramatically before a tsunami arrives. The tide appears to go out when the trough of the tsunami wave arrives before the create, meaning that the tsunami is collect enough sea water to travel through 22. Why it is dangerous to return to the beach after a tsunami wave first arrives. It is dangerous to return to the shore after the first tsunami arrives before than be anywhere from 3-10 waves that occur over many hours 23. What a tsunami seawall is. A concrete wall on the beach that protects the land from tsunami water going too far inland 24. The length of time it takes a tsunami wave to cross the Pacific Ocean. It takes about 1 day for a tsunami wave to cross the Pacific Ocean 25. Why there was a high death toll in the Indonesian tsunami of 2004 around the Indian Ocean. There wasn’t enough education about tsunamis, there was no early warning detection system for tsunamis or any way to warn the public 26. How the DART tsunami early warning system works. A pressure sensor on the seafloor measures the water pressure which is then sent to a buoy and then used to determine if there is risk of a tsunami. Can send out tsunami warnings as quickly as 15 minutes after an earthquake with size and path estimates 27. The process that can cause the largest tsunamis. Asteroid impacts have the potential to create the largest tsunamis, but they are rare. 28. The process that caused the largest tsunami run-up recorded in the past 100 years. A landslide in Litya Bay in Alaska in 1958 caused the largest tsunami run up in the past 100 years 29. The time it takes for a tsunami to travel from the Åkerneset cliffs to Geiranger. A tsunami from the Akernest cliffs would take only 10 minutes to reach Geiranger 30. What generally causes tsunamis generated at the Hawaiian Islands. Underwater landslides currently pose the largest threat for tsunamis to be generated in Hawaii 31. The mostly likely cause of a tsunami to hit the U.S. east coast. The east coast of the US is vulnerable to tsunamis that are generated by underwater landslides initiated from the Canary Islands 32. The cause of the tsunami that killed 36,000 people in Indonesia in 1883. The volcanic eruption of Krakatoa caused a tsunami that killed 36,000 people in Indonesia 33. The vulnerabilities of Florida if a 10-km-diameter asteroid hit the Gulf of Mexico. If a 10 km diameter asteroid hit the Gulf of Mexico, Florida would be completely overrun by water Unit 5 - Volcanoes 2
34. The difference between magma and lava. Magma is below the Earth’s surface, lava is above the Earth’s surface, but they are both melted 35. That there is no ocean of magma beneath the lithosphere. There is no ocean o magma beneath the lithosphere. Most of the mantle is below its melting point and magma only occurs in specific places 36. The temperature of the mantle compared to its melting temperature. Most of the mantle is cooler than it melting point except for a small percentage of magma 37. The processes which will promote the melting of hot rocks. Increase temperature, decrease pressure (depressurized melting causes the melting temperature of rocks to decrease), hydration-induced melting ( adding water causes long silica chains to be broken, reducing the melting temperature of rocks) 38. The type of volcanism found far from plate boundaries. Hot spots are typically found far away from plate boundaries 39. The process that causes hot rocks to melt at subduction zones. Hydration induced melting causes rocks to melt in subduction zones when water from the subducting plate lowers the melting temperature of the mantle above 40. What the Ring of Fire refers to. Refers to the line of volcanoes that wraps around the Pacific Ocean, where the Pacific plate subducting into the surrounding plates 41. Why there are fewer active volcanoes in the southwestern US. There is no active subduction zone in the Southwestern US, which leads to fewer volcanoes there than in the Northwestern US 42. The process that causes hot rocks to melt at hot spots. The base of the mantle is heated by the outer core, causing a plume of solid, buoyant mantle to rise until it reaches the lithosphere, where it begins to melt due to depressurization, causing volcanism 43. Where the rising plume originates from at hot spots. The plume is made up of solid, buoyant mantle that has been heated by the outer core 44. Where a hot spot plume melts. A hot sport plume melts at the base of the lithosphere 45. Why hot spots lead to a line of volcanoes. The hot spot does not move, but the tectonic plate move over them, leaving a trail of volcanoes, such as Hawaii. Once the volcano moves away from the hot spot, the volcano becomes dormant 46. Where hot spot tracks found. All over the world, hot spot tracks on the same plate tend to move in the same manner, showing plate motion 47. The process that causes hot rocks to melt at mid-ocean ridges. Mantle experiences depressurized melting at mid-ocean ridges 48. What viscosity is a measure of. Viscosity is a measure of how easily a fluid flows 49. The kind of volcanos produced by low viscosity lava. Low viscosity lava leads to the formation of shallow sloped shield volcanoes 50. That the big island of Hawaii is the tallest mountain on Earth. True, Mauna Kea on the big island of Hawaii is the tallest mountain on Earth when measured from the seafloor 51. How a stratovolcano forms. Stratovolcanoes form due to alternating layers of pyroclastic flows and high viscosity effusive lava flows 52. The kind of volcano that forms when tephra is thrown out of a volcanic vent. 3
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