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Earthquakes & Volcanoes

Earthquakes & Volcanoes. Earthquakes. Vibrations in the ground that result from movement along breaks in Earth’s lithosphere called faults. Where do Earthquakes Occur?. Most earthquakes occur along plate boundaries. Types of Faults. Normal forces pull two blocks of rock apart

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Earthquakes & Volcanoes

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  1. Earthquakes & Volcanoes

  2. Earthquakes • Vibrations in the ground that result from movement along breaks in Earth’s lithosphere called faults

  3. Where do Earthquakes Occur? • Most earthquakes occur along plate boundaries

  4. Types of Faults • Normal • forces pull two blocks of rock apart • ex. divergent plate boundary • Reverse • forces push two blocks of rock together • ex. convergent plate boundary • Strike-Slip • two blocks of rock slide horizontally past each other • ex. transform plate boundary

  5. Earthquake Epicenter • Seismic Waves - Energy that travels as vibrations on and in the Earth • Focus – where seismic waves originate and where rocks first move along the fault • Epicenter - location on the Earth’s surface where the seismic waves originated

  6. Types of Seismic Waves • Primary (P) Waves • move in a push-pull motion like a spring • fastest-moving waves and the first waves you feel • Secondary (S) Waves • move in an up-and-down motion • slower than P waves • do not travel through liquid • Surface Waves • travel only on Earth’s surface in a rolling motion • most destructive

  7. Studying Earthquakes • Seismologist – scientist that studies earthquakes • Seismometer – instrument used to measure and record ground motion • Earthquake Scales:

  8. Volcanoes • A vent in Earth’s crust through which molten rock (magma) flows • Once magma reaches the surface it is called lava

  9. Formation of Volcanoes • Most volcanoes form at plate boundaries • Convergent • as one plate subducts beneath another the rock melts and rises to the surface • Divergent • As the plates separate magma rises through the vent in Earth’s crust and forms new crust • ex. sea-floor spreading

  10. Hot Spots • Volcanoes not associated with plate boundaries • convection currents in the mantle rise magma to the surface • as plates move over the hot spot island chains are formed • The oldest island is the farthest away from the hot spot • ex. Hawaiian Islands

  11. Types of Volcanoes • Shield Volcano • large, with gentle slopes • form along divergent boundaries or hot spots • Composite Volcano • large and steep-sided resulting from explosive eruptions • form along convergent boundaries • Cinder Cone • Small, steep-sided

  12. Volcanic Eruptions • Quiet Eruptions • magma has a low viscosity (low silica content) • Violent Eruptions • magma has a high viscosity (high silica content)

  13. Effects of Volcanic Eruptions • Pyroclastic Flow • fast-moving avalanches of hot gas, ash, and rock that can reach speeds of up to 100 km/h and temperatures of up to 1000 °C • Lava Flows • Ash Fall • Mudflows

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