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