The Theory of Plate Tectonics

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Across
  1. 2. At a _________ boundary, two plates slide past each other, as at the San Andreas Fault in California.
  2. 6. At a _______ boundary, two plates are moving apart.
  3. 7. the name of the landmass when all of the Earth’s continents were a single giant continent
  4. 10. deep valleys running through the center of mid-ocean ridges
  5. 11. At a _________ zone, one plate sinks beneath another plate resulting in the formation of a chain of volcanic islands or a mountain range.
  6. 15. the uppermost, rigid part of the mantle + the crust; cool solid rock portion of the Earth’s surface
  7. 16. deep valleys in the seafloor
  8. 17. molten rock inside the Earth
  9. 18. At a colliding or _______ boundary, two plates push together.
Down
  1. 1. In the theory of ___________, new crust emerges from the rift valley in a mid-ocean ridge by magma pushing up and causing the seafloor to move away from the ridge on both sides.
  2. 3. The theory of _____________ states that the continents were once a single giant supercontinent that broke apart and drifted apart over time.
  3. 4. hot molten or semifluid rock erupted from a volcano or fissure, or the solid rock resulting from cooling of this
  4. 5. The theory of ________ states that the continents float on the Earth’s molten interior gradually moving over millions of years.
  5. 8. a break or fracture in the ground that occurs when the Earth's tectonic plates move
  6. 9. an elevated area caused by hot magma pushing up at a divergent boundary
  7. 12. massive, rigid slabs of solid rock composed of Earth’s lithosphere floating on the asthenosphere
  8. 13. the layer that includes the top part of the upper mantle; it’s between a solid and molten rock and flows slowly over time
  9. 14. small melting areas within the mantle where thermal plumes cause magma to push up through the crust; often are far from a plate edge