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Virginia Tech - GEOS 1034 - Class Notes - Week 5

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Virginia Tech - GEOS 1034 - Class Notes - Week 5

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background image Tsunami- series of waves caused by the displacement of a large volume of water Have the power to strip the land bare The most common means of generating a tsunami is elastic rebound during a  large subduction zone earthquake Material pushes up entire column of ocean water Transport debris the water picks it up and carries it inland- very dangerous Tsunami waves can have similar heights to larger wind blown waves, but carry a  much larger volume of water and travel much further inland Affect the entire body of water Can catch people inland unaware Tsunami wave mechanics In deep water, tsunami waves have long wavelengths (distance from crest to  crest), low wave heights, and great speed As waves approach shore, they slow down which allows the back of the  wave to catch up to the front Reduced wavelength at shore § Increase in wave height at shore § Tsunami waves break when the wave height is about equal to the water  depth These waves are all part of a single tsunami wave that is so broad it  breaks multiple times as it approaches the shore § Examples Sumatra Tsunami- 2004 Extremely large rupture of 1000 km of subduction zone § Took many hours for it to reach shores § Many deaths due to: Lack of education about tsunamis Lack of an early warning system to detect tsunami Lack of a system to alert the public if a tsunami is suspected or  observed § Japan Tsunami- 2011  Wave heights in open ocean were 1 m or less but reached more than  10 m as they approached the shore § Can put a house on top of a house § Overwhelmed the sea walls § Chilean Earthquake 1961 Hilo, Hawaii destroyed by 3rd tsunami wave  § You are in your car and the street suddenly starts filling rapidly with water. What  should you do? Stay in your car and ride it out Water levels cannot rise more than 50 feet 9/19 Japan Tsunami 20+ meter high tsunamis have occurred 4 times in the past 400 yrs in Japan Dozens of tsunami stones along the coast of Japan warn residents not to  build below them Some are more than 600 yrs old § New tsunami stone for 2011 Tsunami sand (tsunamiitte): a sedimentary unit deposited as the result of a  tsunami Our own tsunami stones are written in sand deposits along entire coast of Pacific  NW Tsunami mitigation One of the Most avoidable natural killer Warning signs Significant seismic shaking near shore: 20-40 minutes before a tsunami hits: head to high ground § Water is drawn out before a tsunami 5-10 minutes before the tsunami hits: get to high ground faster § How to avoid Build ultra-high seawalls § Reduce populations that live near the shore § Don’t build nuclear power plant § DART (Deep ocean Assessment and Reporting of Tsunamis) Early warning system Buoys located in the middle of the ocean that test the rise of  waves § Tsunamis consist of btw 3-10 waves Usually the first one is the weakest, 2nd or 3rd is the most damaging Tsunamis can be caused by anything that displaces a large volume of water  upwards NOT on an underwater transform boundary Distant earthquakes Local earthquakes Landslides Can happen underwater or from mountains § Some of the largest are generated by rockslides into deep water 1905/1034- Norway 10 minutes to get 300 ft above sea level § Alaska- 1958 Highest tsunami run-up ever recorded § US east coast is vulnerable to tsunami generated by underwater  landslides in the Atlantic § Underwater landslides have cause the most tsunamis around Hawaii § Volcanic eruptions Volcano piece (flank) can slide down into water causing  displacement of water § Southern flank of Kilauea Volcano is slowly slumping seaward § Krakatau- 1883 § Asteroid impact Impact with volcanoes Original summit of volcano is perturbed by the eruption The volcano collapses The magma body erupts lava, ashes and gases out of the volcano A lateral blast is produced A pyroclastic flow ensues and crashes into the ocean Pyroclastic flows can also induce a tsunami § Tsunami produce run-up which has an elevation component and a distance  (inundation) component • Impact with asteroids ○ A large (1 km) asteroid impact would generate a 1000 ft high tsunami,  though the wave would break far from shore Questions? 1. What processes associated with subduction zone earthquakes causes a tsunami to  be generated a. Opening of trench b. Seismic shaking c. Underwater volcano d. Elastic rebound 2. The san Andreas fault does NOT have the ability to generate a large tsunami 3. What will happen to a boat in the middle of the ocean if a tsunami wave goes  underneath a. Rise in seconds to low height b. Rise over many minutes to a low height c. Rise in seconds to high height d. Rise in minutes to high height 4. When will waves break when moving towards shore? a. When the water depth is equal to the wave height 5. Which will be the most likely to cause DC to be destroyed by a tsunami a. Asteroid 6. Which will result in a tsunami large enough to damage the east coast? a. Underwater landslide b. Volcano c. Earthquake d. asteroid 7. Which would be the most likely to cause a tsunami that would destroy the NWest  coast? a. Asteroid b. Volcano c. Earthquake d. Underwater landslide 8. Why is it not enough to be a sufficient swimmer in an earthquake? a. The debris 9. How do we know the washington and oregon coast have had large tsunamis a. Tsunami sands i. Dig trenches to find tsunami sands 10. How do we know tsunamis have died form tsunamis a. Hundreds of thousands 11. Why does the coast level drop before a wave reaches the shore a. Gravitational attraction of wave  b. Earthquakes cause the seafloor to drop c. Tsunami causes coast to tilt d. Wave troph arrives before the wave crest 12. What is the reason for the high death toll in 2004 Indonesia earthquake? a. People ignored warning sirens b. Buildings not built to withstand c. No warning systems d. People had never been in a tsunami 13. How long do you have after you feel shaking? a. Couple of minutes b. Couple of seconds c. 10s of minutes d. Fraction of a second 14. Why do people wait to go to the beach after a tsunami hits? a. Several waves b. Water makes everything slippery c. Likely to be debris 15. How does DART work? a. People on shore that should there's a tsunami b. Instruments in ocean that detect wave heights and wave speed c. Seismometer that detects underwater earthquake 16. What caused the largest tsunami in 100 years? a. Asteroid b. Earthquake c. Landslide d. Volcano Week 5 (9/17, 9/19, 9/21) Monday, September 17, 2018 12:20 PM
background image Tsunami- series of waves caused by the displacement of a large volume of water Have the power to strip the land bare The most common means of generating a tsunami is elastic rebound during a  large subduction zone earthquake Material pushes up entire column of ocean water Transport debris the water picks it up and carries it inland- very dangerous Tsunami waves can have similar heights to larger wind blown waves, but carry a  much larger volume of water and travel much further inland Affect the entire body of water Can catch people inland unaware Tsunami wave mechanics In deep water, tsunami waves have long wavelengths (distance from crest to  crest), low wave heights, and great speed As waves approach shore, they slow down which allows the back of the  wave to catch up to the front Reduced wavelength at shore § Increase in wave height at shore § Tsunami waves break when the wave height is about equal to the water  depth These waves are all part of a single tsunami wave that is so broad it  breaks multiple times as it approaches the shore § Examples Sumatra Tsunami- 2004 Extremely large rupture of 1000 km of subduction zone § Took many hours for it to reach shores § Many deaths due to: Lack of education about tsunamis Lack of an early warning system to detect tsunami Lack of a system to alert the public if a tsunami is suspected or  observed § Japan Tsunami- 2011  Wave heights in open ocean were 1 m or less but reached more than  10 m as they approached the shore § Can put a house on top of a house § Overwhelmed the sea walls § Chilean Earthquake 1961 Hilo, Hawaii destroyed by 3rd tsunami wave  § You are in your car and the street suddenly starts filling rapidly with water. What  should you do? Stay in your car and ride it out Water levels cannot rise more than 50 feet 9/19 Japan Tsunami 20+ meter high tsunamis have occurred 4 times in the past 400 yrs in Japan Dozens of tsunami stones along the coast of Japan warn residents not to  build below them Some are more than 600 yrs old § New tsunami stone for 2011 Tsunami sand (tsunamiitte): a sedimentary unit deposited as the result of a  tsunami Our own tsunami stones are written in sand deposits along entire coast of Pacific  NW Tsunami mitigation One of the Most avoidable natural killer Warning signs Significant seismic shaking near shore: 20-40 minutes before a tsunami hits: head to high ground § Water is drawn out before a tsunami 5-10 minutes before the tsunami hits: get to high ground faster § How to avoid Build ultra-high seawalls § Reduce populations that live near the shore § Don’t build nuclear power plant § DART (Deep ocean Assessment and Reporting of Tsunamis) Early warning system Buoys located in the middle of the ocean that test the rise of  waves § Tsunamis consist of btw 3-10 waves Usually the first one is the weakest, 2nd or 3rd is the most damaging Tsunamis can be caused by anything that displaces a large volume of water  upwards NOT on an underwater transform boundary Distant earthquakes Local earthquakes Landslides Can happen underwater or from mountains § Some of the largest are generated by rockslides into deep water 1905/1034- Norway 10 minutes to get 300 ft above sea level § Alaska- 1958 Highest tsunami run-up ever recorded § US east coast is vulnerable to tsunami generated by underwater  landslides in the Atlantic § Underwater landslides have cause the most tsunamis around Hawaii § Volcanic eruptions Volcano piece (flank) can slide down into water causing  displacement of water § Southern flank of Kilauea Volcano is slowly slumping seaward § Krakatau- 1883 § Asteroid impact Impact with volcanoes Original summit of volcano is perturbed by the eruption The volcano collapses The magma body erupts lava, ashes and gases out of the volcano A lateral blast is produced A pyroclastic flow ensues and crashes into the ocean Pyroclastic flows can also induce a tsunami § Tsunami produce run-up which has an elevation component and a distance  (inundation) component • Impact with asteroids ○ A large (1 km) asteroid impact would generate a 1000 ft high tsunami,  though the wave would break far from shore Questions? 1. What processes associated with subduction zone earthquakes causes a tsunami to  be generated a. Opening of trench b. Seismic shaking c. Underwater volcano d. Elastic rebound 2. The san Andreas fault does NOT have the ability to generate a large tsunami 3. What will happen to a boat in the middle of the ocean if a tsunami wave goes  underneath a. Rise in seconds to low height b. Rise over many minutes to a low height c. Rise in seconds to high height d. Rise in minutes to high height 4. When will waves break when moving towards shore? a. When the water depth is equal to the wave height 5. Which will be the most likely to cause DC to be destroyed by a tsunami a. Asteroid 6. Which will result in a tsunami large enough to damage the east coast? a. Underwater landslide b. Volcano c. Earthquake d. asteroid 7. Which would be the most likely to cause a tsunami that would destroy the NWest  coast? a. Asteroid b. Volcano c. Earthquake d. Underwater landslide 8. Why is it not enough to be a sufficient swimmer in an earthquake? a. The debris 9. How do we know the washington and oregon coast have had large tsunamis a. Tsunami sands i. Dig trenches to find tsunami sands 10. How do we know tsunamis have died form tsunamis a. Hundreds of thousands 11. Why does the coast level drop before a wave reaches the shore a. Gravitational attraction of wave  b. Earthquakes cause the seafloor to drop c. Tsunami causes coast to tilt d. Wave troph arrives before the wave crest 12. What is the reason for the high death toll in 2004 Indonesia earthquake? a. People ignored warning sirens b. Buildings not built to withstand c. No warning systems d. People had never been in a tsunami 13. How long do you have after you feel shaking? a. Couple of minutes b. Couple of seconds c. 10s of minutes d. Fraction of a second 14. Why do people wait to go to the beach after a tsunami hits? a. Several waves b. Water makes everything slippery c. Likely to be debris 15. How does DART work? a. People on shore that should there's a tsunami b. Instruments in ocean that detect wave heights and wave speed c. Seismometer that detects underwater earthquake 16. What caused the largest tsunami in 100 years? a. Asteroid b. Earthquake c. Landslide d. Volcano Week 5 (9/17, 9/19, 9/21) Monday, September 17, 2018 12:20 PM

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School: Virginia Polytechnic Institute and State University
Department: Geoscience
Course: Geoscience
Professor: Ying Zhou
Term: Fall 2018
Tags: Tsunami
Name: Week 5 notes
Description: These notes cover tsunamis
Uploaded: 09/24/2018
5 Pages 63 Views 50 Unlocks
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