geologic disasters n..

Geologic Disasters
 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
 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
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 cause fewer deaths than many other natural
 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
 The heat of volcanic activity (geothermal energy) can be
used to provide electricity and heat (Iceland does this.)
 Occur in areas where natural slopes exist (river valleys, hills,
 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.
 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 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
Tsunami (at the coast)
Generation (occurs offshore)
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