Earthquakes

Earthquakes: When the Earth Trembles Earthquakes, tremors and seisms are all caused by movement of the Earth’s crust. The movement of the crust is often caused by friction between two tectonic plates. The friction produces shock waves, also called seismic waves. Earthquakes are generally rapid and can be highly destructive.

Causes of Earthquakes Two tectonic plates collide: Pressure can make the Earth’s crust fold (formation of mountains).

Causes of Earthquakes (cont’d) One of the plates can sink beneath the other (formation of ocean trenches). Major earthquake zone.

Causes of Earthquakes (cont’d) Two tectonic plates move apart: Magma escapes through the fault between the plates. Zone of relatively superficial earthquakes that cause little damage.

Causes of earthquakes (cont’d) Two tectonic plates slide against each other: The plates move along a fault. Zone of serious earthquakes due to the friction of the plates.

Tsunamis Most earthquakes occur under water. These cause enormous tidal waves to form (also called tsunamis). These waves move very fast and get bigger as they approach land.

Earthquake Zones Regions located along the edge of tectonic plates are more vulnerable to earthquakes. Pacific Ring of Fire Mid-Atlantic Ridge Mediterranean Perimeter Great Rift Valley (in Africa)

Textbook p. 331 Memory Check Classwork/Homework Textbook p. 331 Memory Check