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