Earth quakes and Volcanoes

1. Earth Earth quakesand Volcanoes quakes Amole Spectra 2013

2. 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”

3. The Ring of Fire

4. 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

5. 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

7. 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

8. 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)

9. Richter Scale

10. 7.8 magnitude (China)

11. San Francisco, 1906

12. Alaska Earthquake 1964

13. Tsunamis are Ocean Earthquakes

14. 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/

16. 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

17. The Ring of Fire

19. Types of Volcanoes • Shield • Composite • Cinder Cones • Seamounts • Hot spots

20. Shield Volcanoes • Magma rich in iron and magnesium • Flows great distances • Mild and frequent eruptions • Gentle slopes • Some of the largest

21. Shield Volcanoes Mauna Loa, Hawaii

22. 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

23. Composite Volcanoes Mt. Vesuvius, Italy Mt. Rainer, Washington

24. Cinder Cone Volcanoes • Smallest and most abundant • Violent eruptions due to large amounts of trapped gas • Only active for short time • Steepest slopes

25. Cinder Cone Paricutin, Mexico

26. Underwater Volcanoes • Called seamounts • Look like composite volcanoes • Occur at divergent plate boundaries

27. 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

28. The Hawaiian Islands