Environmental Hazards before test 2

Environmental Hazards before test 2 - Tsunamis Samoa 2009o...

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Tsunamis Samoa 2009- o 150+ o Mag 8.0 quake caused this Tidal waves- what we once called them but isn’t what they are Causes o Most common occur as a result of an earthquake o Water does not compress, but is displaced by quakes, volc eruptions, landslides, asteroid impact o Pacific Ocean experiences the most global tsunamis o Tsunamis have very long wavelengths Boats don’t nesesarily feel these in open ocean As the wave gets closer it slows and becomes higher Examples of large Tsunamis o Santoini Greece Caldera Copase o Lisbon, portulgal o Chile o Krakatau, Indonesia Volcanic eruption o Japan earthquake o Unimak Island, Alaska o Lituya Bay, Alaska Rock fall, Huge 524 foot wave Most Frequently caused by subduciton zone earthquakes o Japan o Kamchatka Peninsula o Aleutian Islands o Mexico o Peru o Chile How does subducton zone quakes tsunami occur o Slow disturtion of plate after quake o Bulging occurs and water is displaced o Tsunami waves flow Sumatra Quake o 9.0 Moment mag quake 1946 Magnitude 7.3 quake Aleutian Island, Alska tsunami 9.5 quake Chile, 1960 results in Hawaiian Tsunami Harbors are particulary susceptible to the Impacts of Tsunamis Greatest hazard areas
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o Western S. America Hawaii, Oregon area, Indonesia area, Japan Warning systems o In pacific Basin there is a tsunami warning system o IN Indian ocean there was no tsunami warning system in place Most important for those living in Sri Lanka and India Tsunami Hazards Mitigation o Detection and warning o Structural control- building codes o Tsunami run up mapping o Land use/ community planning- locating towns villages and houseing with known knowledge of susceptibility o Probability analysis- history, prehistory o Education/ hazards perception o Emergency response Far-field tsunamis o Tsunamis that originate far away Near term prediction: local changes in water level o Look for water rushing out Reconstructing prehistoric Tsunamis o Geologic record Snap back of plate can cause land level to decrease Uniformitarianism Present day processes as the key to the past Different sedimentary deposites Diff elevation change Tsunami hazard in the lower 48? o Cascadia trench- triple junction region of subduction o Image of treestumps Evedince of large tsunami in past Look up in book about what happens to land?????? Coastal bulge effect Effects of NW paleotsunamis o Sand sheets deposition as high as 18 meters above sealevel o Flooded forests especially in coast inlets due to coastal bulge effect o Large events every ~500 yr during late Holocene (last 3500 years) o Bulge happening in NW right now? Mass Wasting Tsunamis: o Lituya Bay Rockfall Alaska 1958 Circumscribed ( circular surrounded by land) As the waves wash up the slope it uproots trees and debris line Dated by tree ring dating Mega-landslide tsunamis in prehistory o Past slumps and debris avalanches surrounding the island of Hawaii Tsunamis are not only Marine events
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