physical hazards. volcanoes igneous activity igneous activity – mountains where molten rock...
TRANSCRIPT
Physical Hazards
Volcanoes• Igneous activity –Mountains where molten rock (magma)
reaches the Earth’s surface and is released as lava
• Lava can cover farmland, burn trees, and destroy the beauty of an area• Ash and weathering rocks have
formed the very fertile soil
Volcanoes• Lava can cover farmland, burn trees,
and destroy the beauty of an area• Ash and weathering rocks have
formed the very fertile soil
Road on the Big Island of Hawaii
Mt. St. Helens in Oregon blew off 1350 feet of rock and ash and caused 59 deaths
Before
After
Beautiful scenery as well as geothermal energy
EarthquakesThe vibration of the earth produced by the rapid release of energy
San Andreas Fault
The most studied fault system in the world
Cause of many Earthquakes in CA
• Abrupt movement on an existing fault– Produces shock waves in the earth
• Primary Effects• shaking • vertical & horizontal displacements of ground
Northridge, CA Earthquake 1994
• May cause tidal waves “tsunami”
Indonesia Tsunami Dec. 26, 2004
Trigger movement of soil like slumps, rockslides, mudflows, subsidence, and landslides.
How Earthquakes are measured
• Richter scale–Measured in magnitude• amount of energy released–one magnitude increase = 30 times energy
increase»magnitude of 6.5 releases 30x more
energy than 5.5 »900X more energy than 4.5
Global Distribution of epicenters for the past century
Tornados• Intense cyclonic storm
with exceedingly high winds
• Tear up soil, uproot trees and other vegetation
Distribution in the U.S.
Hurricanes
• Tropical cyclonic storms having winds in excess of 74 mph
• Wind blows away topsoil, trees, buildings• Storm surge crashing waves wash soil away• Inland flooding storm surge causes erosion
Floods• The result of water overflowing its banks • Most often occurs because of heavy rain– May occur due to storm surge during hurricanes
Floods
• Greatest erosion and transportation of sediment occurs during a flood– Floods can carry a much larger load (clay and silt particles)
• The fertile soil is taken away and deposited in flood plains– Results in the world’s best farmland along the banks of rivers