Physical Hazards

Volcanoes Igneous activity 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 Lava can cover farmland, burn trees, and destroy the beauty of an area Ash and weathering rocks have formed the very fertile soil Ash and weathering rocks have formed the very fertile soil

Volcanoes Lava can cover farmland, burn trees, and destroy the beauty of an area Lava can cover farmland, burn trees, and destroy the beauty of an area Ash and weathering rocks have formed the very fertile soil 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

Earthquakes The 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 Abrupt movement on an existing fault – Produces shock waves in the earth Primary Effects Primary Effects shakingshaking vertical & horizontal displacements of groundvertical & 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 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