Exam 2 Study Guide

.docx

School

Purdue University *

*We aren’t endorsed by this school

Course

106

Subject

Geology

Date

Dec 6, 2023

Type

docx

Pages

6

Uploaded by PrivateMetal8116

Report
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. Being a good swimmer will not help if you are crushed by a house 2. The process associated with subduction zone earthquakes that causes a tsunami to be generated. A tsunami is a wave caused by the displacement of a large volume of water, most often by subduction zone earthquakes 3. The direction an island above a subducting plate moves between earthquakes. An island above a subduction zone subsides (sinks) as the overriding plate is drawn down by the locked plate interface. During an earthquake, the overriding plate experiences elastic rebound, causing the island and water above to suddenly rise. 4. The magnitude a subduction zone earthquake has to be to generate a large tsunami. Earthquake generated tsunami are generally associated with a M9 or larger earthquake that ruptures 100s of miles of a fault, leading to big tsunami waves hitting 100s of miles of coastline. 5. That tsunami waves traveling through the deep ocean are influenced by seafloor topography. Because a subduction zone tsunami is initiated on the seafloor, it involves the full depth of the ocean. Thus, tsunami waves are influenced by seafloor topography (called bathymetry), which complicates wave propagation. 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 can have similar heights to large wind-blown waves, but carry a much larger volume of water, have a much longer wavelength (distance from crest to crest), and travel much further inland. 8. What happens to a tsunami wave speed and height as it approaches the shore. In deep water tsunami waves have long wavelengths, low wave heights. As waves approach the shore they slow down, which causes the back of the waves to catch up to the front, reducing wavelength, but increasing wave height. 9. What happens to the distance between tsunami wave crests as they approach the shore. The distance between tsunami wave crests decreases as they approach the shore. This is because the wavelength of a tsunami decreases as the water depth decreases. 10. What “tsunami” translates to in Japanese. Harbor wave 11. What happens to a boat in the middle of the ocean when a tsunami wave passes underneath. A boat in the middle of the ocean would rise less than a meter over a period of 10s of minutes and thus not even know that a large tsunami passed underneath. 12. When a wave moving toward shore typically breaks. Tsunami waves (like wind blown waves) break when the wave height is about equal to the water depth. 13. Why inlets (natural harbors) are particularly dangerous places when a tsunami hits. Inlets (natural harbors) are particularly dangerous places when a tsunami hits because the incoming water becomes trapped and piles up. 14. That an earthquake on the San Andreas Fault cannot cause a tsunami. The San Andreas is a strike-slip fault and thus cannot generate a significant tsunami. 15. That tsunami waves can be extremely deadly even many miles inland from the shore. True 1
16. The approximate number of people killed by tsunamis in the past 1000 years. Several hundred thousand people have been killed by tsunamis — but today this is potentially one of the most avoidable natural hazards 17. That the 2011 Japan tsunami was not unprecedented in Japan’s history. True 18. What a Japanese tsunami l is. Dozens of Tsunami Stones along the coast of Japan warn residents 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 reveal a history of large tsunamis 20. The time it takes from earthquake to a tsunami reaching the nearest coastline. Significant seismic shaking near the shore: 20-40 minutes before a tsunami hits Head to high ground. 21. Why sea level drops dramatically before a tsunami arrives. Tsunami waves are often preceded by coastal waters being dragged out when the trough arrives before the crest. 22. Why it is dangerous to return to the beach after a tsunami wave first arrives. Tsunami consist of 3-10 waves, and often the 2nd or 3rd wave is the largest — don’t go back to the shore until given the all clear or at least many hours have passed. A combination of earthquake rupture complexity, rebound off the near shore, and the effects of seafloor bathymetry cause multiple tsunami waves. 23. What a tsunami seawall is. Japan has built seawalls near the shoreline to keep tsunami waters from reaching inland. 24. The length of time it takes a tsunami wave to cross the Pacific Ocean. 7 hours. 25. Why there was a high death toll in the Indonesian tsunami of 2004 around the Indian Ocean. These people could have been saved through education about tsunamis and a system to notify the public if a tsunami is suspected – all doable 26. How the DART tsunami early warning system works. Pressure sensor on the seafloor. 27. The process that can cause the largest tsunamis. Any process that displaces a large volume of water. 28. The process that caused the largest tsunami run-up recorded in the past 100 years. Landslide 29. The time it takes for a tsunami to travel from the Åkerneset cliffs to Geiranger. 10 minutes. 30. What generally causes tsunamis generated at the Hawaiian Islands. Underwater landslides 31. The mostly likely cause of a tsunami to hit the U.S. east coast. the Americas are vulnerable to tsunamis generated by underwater landslides on the flanks of volcanoes like the Canary Islands, which have very steep underwater cliff faces 32. The cause of the tsunami that killed 36,000 people in Indonesia in 1883. The 1883 the volcanic eruption of Krakatoa caused a tsunami that killed 36,000 people in Indonesia as the volcano is surrounded by a lot of shoreline. Original size of Krakatoa prior to the eruption. 33. The vulnerabilities of Florida if a 10-km-diameter asteroid hit the Gulf of Mexico. You would not survive. Unit 5 - Volcanoes 34. The difference between magma and lava. Magma is transported to the surface where it flows out as lava or explodes as ash and pyroclastic flows. 35. That there is no ocean of magma beneath the lithosphere. Tectonic plates do not float over an ocean of molten rock. 2
36. The temperature of the mantle compared to its melting temperature. Most of the mantle is below its melting temperature. Magma (melted rock) only occurs in very specific places and comprises only a very small percentage of the mantle. 37. The processes which will promote the melting of hot rocks. 1. Increase temperature: While this could work to melt rocks, there are few processes in the crust that will cause rocks to heat up, so this is not a common way to induce volcanism. 2. Decrease pressure (called depressurized melting): This reduces the melting temperature of rocks, which experience a decrease in pressure if they rise closer to the surface, thus enabling already hot rocks to melt. 3. Add water to the mineralogy (called hydration-induced melting). This breaks up long silica chains, which reduces the rock’s melting temperature and thus can cause already hot rocks to melt. 38. The type of volcanism found far from plate boundaries. Hotspot volcanism. 39. The process that causes hot rocks to melt at subduction zones. Hydration induced melting 40. What the Ring of Fire refers to. Subduction zone volcanism occurs everywhere plates are subducted, causing a “Ring of Fire” around the Pacific Ocean. 41. Why there are fewer active volcanoes in the southwestern US. Because there is no active subduction zone in the southwestern US, there are fewer active volcanoes compared to the northwestern US. 42. The process that causes hot rocks to melt at hot spots. Decompression Melting Hot spot volcanism begins when the base of the mantle is heated by the outer core, causing a hot (but still solid), buoyant plume of mantle to rise. When the hot spot plume head reaches the base of the lithosphere, it begins to melt by depressurized melting, causing massive volcanism. 43. Where the rising plume originates from at hot spots. Base of mantle is heated by outer core. 44. Where a hot spot plume melts. When it reaches the base of the lithosphere. 45. Why hot spots lead to a line of volcanoes. As hotspot is stationary but as a tectonic plate moves over it, the volcano that is created at the hotspot is carried with the plate. 46. Where hot spot tracks found. Hotspot tracks are found all over the world. 47. The process that causes hot rocks to melt at mid-ocean ridges. Depressurized melting. 48. What viscosity is a measure of. A measure of how easily a fluid flows. 49. The kind of volcanos produced by low viscosity lava. Broad shallow sloped volcanoes. High viscosity lave = narrow high sloped volcanoes. 50. That the big island of Hawaii is the tallest mountain on Earth. Mauna kea. Is the tallest mountain on earth. 51. How a stratovolcano forms. Stratovolcanoes are midsized volcanoes that form due to alternating layers of pyroclastic flows (debris from explosive eruptions) and high viscosity effusive lava flows. 52. The kind of volcano that forms when tephra is thrown out of a volcanic vent. Very high viscosities lead to cinder cone volcanoes, small volcanoes built when tephra (air cooled lava fragments) are thrown out of a volcanic vent. 3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help