Geological Hazards and Their Impact_McGeary_Date_041910

Geological Hazards and Their Impact_McGeary_Date_041910 -...

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Unformatted text preview: ← 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: • 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 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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This note was uploaded on 08/30/2010 for the course GEOL 105 taught by Professor Kohut during the Spring '08 term at University of Delaware.

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Geological Hazards and Their Impact_McGeary_Date_041910 -...

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