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Learn about earthquakes, seismic waves, Richter Scale, volcanoes, types of eruptions, and volcanic islands. Discover the Ring of Fire geological features. Find out how seismic waves provide insights into Earth's interior.
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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