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Plate Tectonics

Plate Tectonics. Bellringers!! . Bellringer 11/11-12. Define plate tectonics: Use ONE word to describe the Lithosphere: Asthenosphere: Which contains the plates? L or A Which has convection currents? L or A Which has oceanic crust? L or A Which is HOTTER ? L or A.

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Plate Tectonics

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  1. Plate Tectonics Bellringers!! 

  2. Bellringer 11/11-12 • Define plate tectonics: • Use ONE word to describe the • Lithosphere: • Asthenosphere: • Which contains the plates? L or A • Which has convection currents? L or A • Which has oceanic crust? L or A • Which is HOTTER? L or A

  3. Bellringer 11/15 • How do heated currents (of molten rock, water, etc.) tend to move in natural systems, and WHY? • What process drives the movement of tectonic plates? • How will lithospheric plates that are directly above a rising current move? • Together or Apart • How will plate above a sinking current move? • Together or Apart

  4. Bellringer 11/16 • What theory suggests that South America and Africa were once part of a larger continent that broke and moved apart? • Who was the German scientist who proposed the most famous version of this theory? • List 3 lines of evidence he used to support his theory.

  5. Bellringer 11/17 • What do we know about the distribution of earthquakes and volcanoes on Earth? a. They occur randomly across the world b. Quakes tend to happen along plate boundaries but volcanoes are random c. Both quakes and volcanoes tend to occur at plate boundaries • What type of boundary is the most “active”? • Convergent • Collision • Subduction • Magnetic minerals in undisturbed rocks will • Indicate where “north” was at the time of formation • Align with “north” as we know it to be now, no matter what • Change in their direction of alignment slowly over time

  6. Evidence for Plate Tectonics Theory Earthquakes and Volcanoes Magnetism Heat Flow and Seafloor Elevation

  7. 1. Earthquakes and Volcanoes • Earthquakes • Occur in limited belts around the world • These same belts also contain most of Earth’s volcanoes • These belts locate plate boundaries

  8. Plate boundaries are active areas • This is where plates are moving! • Stress from friction builds up  causes fractures  earthquakes • Heat flow as plates subduct  rising magma to surface  volcanoes above plate boundaries

  9. “Ring of Fire” • World’s largest belt of volcanoes and earthquakes, nearly surrounds the Pacific Ocean • 90% of earthquakes occur here • Many famous volcanoes

  10. 2. Magnetism • Magnetic minerals in rocks record the direction of the Earth’s poles when they were formed • Found that Earth’s crust had drifted or shifted since the time many rocks were formed

  11. There is evidence Earth’s magnetic poles often reversed. • North Pole ‘became’ the South Pole, and vice-versa

  12. Magnetic Polarity Reversals • Show in bands in the igneous rock on the ocean floor, where plates are moving apart • Age dating found that the youngest rocks are at plate boundaries where plates are spreading apart • Rock gets older away from these boundaries

  13. Spreading Centers • Found on ocean floors • Where plates are moving apart • Lava wells up, continuously forming new oceanic crust • Older crust moves away in both directions, carrying continents with it

  14. 3. Heat Flow and Seafloor Elevation • If convection currents within the asthenosphere drive plate movement, then evidence for this should be found at spreading centers… • Heat Flow: the measure of the amount of heat leaving the rocks of the lithosphere. • Unusually high at spreading centers • Decreases away from them

  15. Elevation of the seafloor • Heated materials expand…it has been found that spreading centers have higher elevations than the rest of the seafloor • Elevations decrease away from spreading centers as the crust cools and contracts (shrinks back down)

  16. Generalization- Evidence for P.T. • If spreading centers create new crust constantly, does that mean the earth is getting bigger? • Describe the age of rocks at a spreading center? • How does heat flow support plate tectonics theory? • Why do we see higher elevations at “mid-ocean ridges”?

  17. Bellringer 11/19 What type of plate boundary is it??? • Where plates are pulling apart • Plates sliding past each other • Boundary where you will see mountains • Boundary that creates mid ocean ridges • San Andreas Fault • Mid-Atlantic Ridge • Where we see lots of quakes and volcanic activity

  18. Bellringer 11/22 • What type of boundary produced the San Andreas Fault? • What is a famous example of a divergent boundary? • What type of boundary produced the Himalayas? Where are they located? • Give a famous example of a subduction boundary. List the continental and oceanic crusts involved.

  19. Bellringer 11/23 • Label the tectonic plates

  20. Bellringer Collection- 7 pts total • 11/11 or 12 • 11/15 • 11/16 • 11/17 • 11/19 • 11/22 • 11/23

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