Earthquakes Lets Get Quakin KWL Earthquakes Activity at

Earthquakes Let’s Get Quakin’

KWL Earthquakes

Activity at Plate Boundaries • At plate boundaries (the edges of plates), we have: • Earthquakes • Volcanoes • Mountain building

Earthquakes San Francisco Earthquake 1910 • Earthquakes are a sudden shaking of the ground caused by the movement of plates. • Earthquakes occur along faults. – Faults are cracks in the crust where plates move past each other.

Stress • Sometimes the rocks in the plates stick together. As the plates continue to move, the rocks get stressed. • When the rocks break free, the stress is released in a big shake that we feel as an earthquake.

Earth’s Plates • Most earthquakes occur along tectonic plate boundaries. – Question: • Where are the most earthquakes happening? • The least?

• Earthquakes occur along faults, like the San Andreas Fault between the Pacific Plate and the North American Plate. Faults San Andreas Fault (California)

Types of Faults • Along the boundary separating any two Divergent: plates, the relative Pulling motion between the plates can be Convergent: classified into one of Pushing 3 categories Transform: Sliding

Seismic Waves • Earthquakes generate seismic waves, which are vibrations.

The Seismograph • Earthquakes generate seismic waves which can be detected with a sensitive instrument called a seismograph.