Earthquakes and Volcanoes C12-17 and C20-25 v.martinez

1. Earthquake An earthquake is a vibration, or shaking of Earth’s crust.

2. Fault A fault is a break in the crust along which the rocks move.

3. Focus The focus is the point underground where the movement first took place.

4. Epicenter The epicenter is the point on the surface that is right above the focus.

5. Seismograph A seismograph is an instrument that records earthquake waves.

7. Why do earthquakes occur? There is a build up and sudden release of energy in rocks.

8. Where do most earthquakes occur? Most earthquakes occur along faults.

8. The San Andreas Fault The San Andreas Fault is in California. Dozens of major earthquakes occur here.

9. Volcano A volcano is a mountain that forms when red-hot melted rock flows through a crack onto the earth’s surface.

10. Magma Magma is melted rock inside the earth.

11. Lava Lava is melted rock that reaches the earth’s surface.

12. Vent The magma flows onto the surface through a rock opening called a vent to form volcanic mountains.

13. Magma Chamber A magma chamber is an underground pool that holds hot magma.

15. What are the three ways volcanoes form? 1. When two plates collide 2. When two plates separate 3. When plates move over hot spots in the mantle

Plates colliding

Plates separating

Plates moving over hot spots in the mantle