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Earth. Earth quakes and Volcanoes. quakes. Amole Spectra 2013. What are ?. Earthquakes. The resulting vibrations that occur from rocks sliding past one another at a fault Caused by pressure experienced at plate boundaries Energy is released as seismic waves
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Earth Earth quakesand Volcanoes quakes Amole Spectra 2013
What are ? Earthquakes • The resulting vibrations that occur from rocks sliding past one another at a fault • Caused by pressure experienced at plate boundaries • Energy is released as seismic waves • Seismic waves create the “shaking”
Earthquake Features • Focus- exact point inside Earth where quake originates • Epicenter- Point on surface directly above focus • Energy travels outward from these points in the form of waves
Types of Seismic Waves • Primary or P waves- • Longitudinal • From focus • Fastest (arrives first) • Secondary or S waves- • Transverse wave • From focus • Slower (arrives second) • Surface waves or L waves- • Circular motions • Up and down • Back and forth • From epicenter • Moves across surface • Slowest (arrives last) • Most destructive
Measuring Earthquakes • Three Seismograph • Difference between arrival times allows seismologists to calculate the distance to the epicenter • Draw three circles with radii being the distance to epicenter. • The overlapping is the location of the epicenter
Measuring Earthquakes • The Richter Scale is used to measure the energy (magnitude) of the earthquake • Does not predict severity/damage • Building construction • Depth of focus • Soil composition and saturation • Type of rock • Mercalli scale rates the quakes effect of surface (intensity)
Seismic Waves and Earth’s Interior • Seismic waves can be used to investigate the Earth’s interior. http://www.pbs.org/wnet/savageearth/animations/earthquakes/
What is a Volcano? • An opening in Earth’s crust through which magma has reached the Earth’s surface • Release molten rock, ash, and gases • Often form hills or mountains as lava builds and cools • Generally have one central vent • Magma that reaches the surface is called lava • Most occur at convergent plate boundaries
Types of Volcanoes • Shield • Composite • Cinder Cones • Seamounts • Hot spots
Shield Volcanoes • Magma rich in iron and magnesium • Flows great distances • Mild and frequent eruptions • Gentle slopes • Some of the largest
Shield Volcanoes Mauna Loa, Hawaii
Composite Volcanoes • Alternating layers of ash, cinder, and lava • Magma rich in silica • Trapped gases cause eruptions that alternate between flows and explosions of cinder and ash • Steeper slopes
Composite Volcanoes Mt. Vesuvius, Italy Mt. Rainer, Washington
Cinder Cone Volcanoes • Smallest and most abundant • Violent eruptions due to large amounts of trapped gas • Only active for short time • Steepest slopes
Cinder Cone Paricutin, Mexico
Underwater Volcanoes • Called seamounts • Look like composite volcanoes • Occur at divergent plate boundaries
Hot Spots • Occur in the middle of plates • Mantle plumes melt as the rise from the mantle and erupt • Mantle plumes under oceans create islands from ash and lava that builds up and breaks through the surface • As the plate moves the mantle plume stays creating a chain of extinct volcanic islands