1. Volcanoes and Earthquakes

2. What is a volcano? Weak spot in crust where molten material (magma) comes to the surface

3. Volcanoes and Plate Boundaries What are plate tectonics? theory which describes the motions of the earth’s crustal plates What causes plate tectonics? convection currents in the mantle Volcanic belts around plate boundaries Ring of Fire Converging plate boundaries Plates come together Diverging plate boundaries Plates seperate

5. Hot Spot Volcanoes Magma erupts through Earth’s crust Can happen anywhere Yellowstone

6. Volcanic Eruptions Quiet Eruptions Low-silica, low-viscosity magma Hawaii Explosive Eruptions High-silica, high viscosity Pyroclastic flow Mt. St. Helens

7. Volcano Life Cycle Active-is erupting or may erupt at any time Dormant- Might become active in future Extinct- dead, unlikely to erupt again

8. Volcano Energy Energy comes from magma under Earth Hot Springs- groundwater heated by magma and forms pool Geysers- Hot water, steam erupts from ground Geothermal energy- water heated naturally Used to warm houses electricity (steam)

10. What is an earthquake? Shaking and trembling that results from the movement of rock beneath Earth’s surface

11. Stress in Earth’s Crust Tension- stretches rock, divergent Compression- Squeezes rock until it folds or breaks, convergent Shearing- rocks move in opposite directions

12. Faults Normal Faults- diverge, footwall above hanging wall Reverse Faults- Compression, hanging wall above footwall, converge Strike-slip Faults- plates move past each other

14. Seismic Waves Carry energy from an earthquake away from the focus (center) through Earth’s interior, and across surface

15. Types of Seismic Waves P waves- first to arrive, longitudinal waves, move in solids and liquids S waves- second to arrive, transverse waves, only in solids Surface waves- ground moves like ocean waves, transverse waves

17. Seismograph Detects seismic waves Used to map and monitor faults

18. Damage from Earthquakes Shaking- triggers landslides, avalanches, destroys buildings and water mains Liquefaction- loose, soft soil turns to mud Aftershocks- smaller earthquakes following big earthquake Tsunamis- large wave