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Earthquakes

Earthquakes. Chapter 6 Section 1. Section 6.1 – Earthquakes and Plate Tectonics. Earthquakes occur when rocks under stress suddenly shift along a fault. The rocks from both sides of the fault are pressed together and cannot move.

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Earthquakes

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  1. Earthquakes Chapter 6 Section 1

  2. Section 6.1 – Earthquakes and Plate Tectonics • Earthquakes occur when rocks under stress suddenly shift along a fault. • The rocks from both sides of the fault are pressed together and cannot move. • When the stress becomes to great the rocks will suddenly grind past each other

  3. Section 6.1 – Earthquakes and Plate Tectonics • The elastic rebound theory says that rocks are stressed and will break at their weakest point and spring back to their original shape. • As they break and move they release seismic waves • The seismic waves cause other rocks to break and spring back. These are known as aftershocks

  4. Section 6.1 – Earthquakes and Plate Tectonics • The area of the fault where the first slippage occurs is the focus • The point on the earth’s surface above the focus is called the epicenter

  5. Section 6.1 – Earthquakes and Plate Tectonics • 90 percent of continental earthquakes have a shallow focus within 70 km of the surface (about 44 miles) • Intermediate focus earthquakes are between 70 km and 300 km (44 miles to 186 miles) • Deep focus quakes are between 300 km and 650 km (186 miles to 404 miles)

  6. Section 6.1 – Earthquakes and Plate Tectonics • Most earthquakes occur along the edges of plates. • There are 3 major earthquake zones • The largest is the Pacific Ring of Fire • It is the border of the Pacific Plate where is touches the North and South American plates, Asian Plate, and the Australian Plate

  7. Section 6.1 – Earthquakes and Plate Tectonics • The second major zone is along the mid-ocean ridges. • The third major zone is between Europe and Africa

  8. Section 6.1 – Earthquakes and Plate Tectonics • A fault zone is an area where several plates are touching • The San Andreas Fault is actually several faults that all connect to form one long fault zone

  9. Section 6.1 – Earthquakes and Plate Tectonics • Not all earthquakes happen on plate boundaries • The most wide felt earthquake in the United States occurred in New Madrid, Missouri in 1812 • There is an ancient fault zone deep within the North American Plate along the Mississippi River region. • China also has earthquakes in the middle of the Asian plate

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