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Chapters 10 & 11

Chapters 10 & 11. Tsunamis. What?. What is a tsunami? What triggers tsunamis?. A massive volume of seawater in motion Volcanic eruptions, landslides, earthquakes, and impacts by asteroids or comets. How?. How does an earthquake create a tsunami?.

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Chapters 10 & 11

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  1. Chapters 10 & 11 Tsunamis

  2. What? • What is a tsunami? • What triggers tsunamis? • A massive volume of seawater in motion • Volcanic eruptions, landslides, earthquakes, and impacts by asteroids or comets

  3. How? • How does an earthquake create a tsunami? • It is usually near a fault line where two tectonic plates meet • One of these plates moves up or down and displaces the ocean water above it

  4. Where?

  5. How? • How large are tsunamis? • In the open ocean, they… • Are very long waves spanning 100’s of km • Are not very high, usually only a few cm • Can move up to speeds of 1000 km/h (622 mph)

  6. Why? • Why are they so large near the coast? • Tsunami waves slow down as they approach a coast • The waves bunch together (smaller λ), which causes them to gain height (amplitude)

  7. How? • How large can a tsunami wave get? • Near the epicenter: • Avg. 30 m (100 ft.) • Away from the epicenter: • Avg. 15 m (50 ft.) • The first wave may not be the largest

  8. Where?Lituya Bay, Alaska – 1958

  9. Where?Lituya Bay, Alaska – 1958 The same topography that leads to the heavy tidal currents also created the highest wave from a tsunami in recorded history. On July 9, 1958, an earthquake caused a landslide in the Crillon Inlet at the head of the bay, generating a massive mega tsunami measuring 524 m (1,719 ft). For comparison, the Empire State Building is 448 m (1,470 ft) high including its antenna spire. The wave possessed sufficient power to snap off all the trees up to 1,720 feet (520 m) high around the bay. Most of these were spruce, and most were 6 feet (1.8 m) thick. The wave stripped the soil down to the bedrock around the entire bay. There were three fishing boats anchored near the entrance of Lituya Bay on the day the giant wave occurred. One boat sank and the two people on board were killed. The other two boats were able to ride the waves. Based on Swanson's description of the length of time it took the wave to reach his boat after overtopping Cenotaph Island near the bay's entrance, the wave may have been traveling up to 600 mph. When it reached the open sea, however, it dissipated quickly.

  10. Where?Lituya Bay, Alaska – 1958

  11. How? • How far inland can a tsunami wave travel? • It depends on the costal geography • The flooding usually occurs up to 1 km (0.5 mi) inland covering the land with water and debris

  12. How? • How often do these events happen? • There is no way to tell • But there are about 3-4 pacific wide tsunami’s every century

  13. How? • How are tsunami’s detected? • Deep-ocean Assessment and Reporting of Tsunamis (DART) • Allow for adequate warning to be given in the event of a possible tsunami

  14. How?

  15. Where?12/26/2004 – Indian Ocean

  16. Where?12/26/2004 – Indian Ocean • Cause: 9.0 M earthquake (30 ft. displacement) • Equivalent to hundreds of billions of TNT • Wave Speed: 800 km/h or 500 mph • Wave Height: 10 m • Distance Traveled Inland: 1 km • Casualties: 230,000 • Deadliest tsunami on record

  17. Where?2/27/2010 – Chile

  18. Where?2/27/2010 – Chile Cause: 8.8 M earthquake Wave Height: 3 m Distance Traveled Inland: 2000 m Casualties: 212,000 (some from earthquake)

  19. Where?2/22/2011 – New Zealand

  20. Where?2/22/2011 – New Zealand • Cause: 6.3 M earthquake • Triggered 30 million tons of ice to fall off Tasman Glacier • Wave Height: 3.5 m • Casualties: 200 (all from earthquake)

  21. Where?3/11/2011 – Japan

  22. Where?3/11/2011 – Japan Cause: 9.0 M earthquake Wave Speed: 1000 km/h or 622 mph Wave Height: 24 m Distance Traveled Inland: 10 km Casualties: 18,500 (more missing)

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