vocab words

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Across
  1. 4. the process by which the oceanic crust sinks beneath a deep-ocean trench
  2. 5. of plate tectonics a theory stating that Earth's lithosphere is broken into huge plates
  3. 6. trench a deep valley along the ocean floor
  4. 7. crust is 6-7 km thick
  5. 8. oceanic crust is made up of this
Down
  1. 1. continental crust is made up of this
  2. 2. ridge an undersea mountain chain where new ocean floor is produced
  3. 3. crust a crust 20-50 km thick