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Geological Hazards and Their Impact_McGeary_Date_041910

Geological Hazards and Their Impact_McGeary_Date_041910 -...

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Tsunami - a tsunami is a large displacement of water - causes: offset of sea floor by earthquakes, landslides, major volcanic eruptions, impact most commonly caused by thrust faults at subduction zones - different from normal waves: have height (at least 1m) 360 km wave length (versus 100 m) travel at 500-600 mph (versus 50 mph) - as tsunamis come into shallow coastal water they can significant height 5-10 m major 10 m or > great - run up: the height of water that a wave reaches onshore can be up to 30 m (Chile) - warning systems earthquake detectors, water height detectors (tidal gauges, buoys, deep water sensors), communication, education far-field tsunami can be 100% warned about (tsunami that occur far from the source that generated them) if the region has invested in the technology it is possible to warn people, however, the warning usually doesn’t come until within the hour the tsunami will come local systems can get warnings to you the close you are to the source people still die because of curiosity - tsunamis are so dangerous because:
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not every earthquake produces a tsunami hard to model actual height may be too close to epicenter of earthquake for a warning first wave is not always the biggest lack of education human curiosity (about seeing the wave) - megaquake along the Cascadia subduction zone in 1700 caused a major tsunami we know this because from Japan’s tsunami records (occurred in January of 1700) occur every few hundred years and come ashore within 20 minutes of the earthquake U.S. should worry about tsunami potentially reaching 20 m. however, warning technology will help save lives Volcanoes Magma: molten (liquid, melted) rock Lava: magma that flows on Earth’s surface Pyroclasts: exploded magma (ash, cinder, pumice, bombs) - 3 processes that melt rock: increase temperature, drop pressure (decompression melting; main process), add water - 3 types of volcanic rock basalt: low silica content, dark in color, low viscosity o mostly lave flow o non-explosive andesite: intermediate silica content, viscosity, and color
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o some lava flows, ash, rubble rhyolite: high silica content, light in color, high viscosity o mostly ash o explosive (need the pressure of the gas and inability of it to escape between
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  • Spring '08
  • KOHUT
  • Volcano, volcanic hazards, silica content, major volcanic eruptions, lahar- volcanic mudflow, water height detectors

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