AmoleSpectra2013

What are ? 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”

The Ring of Fire

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)

MagnitudeEarthquake EffectsEstimated Number Each Year 2.5 or less Usually not felt, but can be recorded by seismograph. 900, to 5.4 Often felt, but only causes minor damage. 30, to 6.0 Slight damage to buildings and other structures to 6.9 May cause a lot of damage in very populated areas to 7.9 Major earthquake. Serious damage or greater Great earthquake. Can totally destroy communities near the epicenter. One every 5 to 10 years Richter Scale

7.8 magnitude (China)

San Francisco, 1906

Alaska Earthquake 1964

Tsunamis are Ocean Earthquakes

Seismic Waves and Earth’s Interior FactObservationTheory Waves change speed and direction when the density of the medium changes Velocity of seismic waves are different t different locations The Earth is composed of different layers containing different materials S waves are transverse and cannot pass through liquids S waves do not reach the side of Earth’s core opposite the focus Part of the Earth’s core must be liquid Seismic waves can be used to investigate the Earth’s interior.

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

The Ring of Fire

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

The Hawaiian Islands