geologic disasters n..

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Geologic Disasters
Earthquakes
 Most violent and sudden of the geologic disasters
 Occur most often along the edge of tectonic plates
 Most deaths and injuries occur because of buildings
collapsing
 Afterward, injured people may die due to lack of medical
aid, food, water and shelter, as well as fires or disease
 Earthquakes cause more damage and deaths in LDCs
because
o cities are more crowded (high population density)
o lower building standards
o no plans or few services ready for disaster relief
o less money for disaster relief
Volcanoes
 Volcanoes cause fewer deaths than many other natural
disasters.
 Generally some activity (earth trembles, smoke, ash)
occurs before an eruption to warn people to leave.
 Sometimes the eruption is violent and sudden – these
eruptions are the most dangerous.
 Most deaths in sudden eruptions are caused by
pyroclastic flow – clouds of superheated gas.
 Deaths afterward occur due to fires started by the
eruption or famine due to loss of crops.
 Damage due to large amounts of ash and cinders, fires, or
lava flows.
 Can cause world-wide effects: cooler weather and acid
rain.
 The heat of volcanic activity (geothermal energy) can be
used to provide electricity and heat (Iceland does this.)
Landslides
 Occur in areas where natural slopes exist (river valleys, hills,
mountains).
 May be called rockslides, landslides, mudslides, etc.
 A “triggering event” causes rock or soil to move rapidly
down the slope.
 Triggering events can include:
o earthquakes
o heavy rainfall
o loss of natural vegetation (plant and forest cover)
o mining or road construction
 Damage property and structure by fast speed of movement
and weight of soil or rock.
 Deaths caused by being buried or crushed.
Avalanches
 Occur where snow and ice accumulate on slopes.
 Can be triggered by human activity or natural causes, such
as temperature change.
 Are less frequent and affect smaller areas than other types
of slides.
Tsunamis
 Tsunamis are caused by slides, earthquakes or volcanoes on
the ocean floor.
 Waves do not seem very large on the open water, but the
height increases as they approach land.
 Waves up to 30m high and speeds over 200 km/hour
Volcanoes
http://gsc.nrcan.gc.ca/volcanoes/images/fig31_e.gif
Landslides
http://www.satimagingcorp.com/media/images/natural-hazards-5.jpg
Tsunamis
www.indiana.edu/~pepp/earthquakes/images/sumatra12_26_04/tsunami_traveltime_local.jpeg
Tsunami (at the coast)
Propagation
Generation (occurs offshore)
http://users.skynet.be/envirconsult/tsunami/propagation_tsunami.gif
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