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Across 2. Vibrations that travel through the Earth carrying the energy released during an earthquake. 8. An undersea mountain chain where new ocean floor is produced. 10. _____ boundary - a plate boundary where two plates move past each other in opposite directions. 11. Dense sphere of solid iron and nickel at the center of the Earth. 12. The theory that pieces of Earth's lithosphere are in constant motion driven by the convection currents in the mantle. 14. The soft layer of the mantle on which the lithosphere floats. 17. Remains of an ancient plant or animal. 19. A deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle. 22. Light-colored igneous rock found in continental crust. 23. A dark, dense igneous rock with a fine texture, found in oceanic crust. 24. The force exerted on a surface divided by the area over which the force is exerted.

Down 1. Layer of hot, solid material between Earth's crust and core. 3. The process by which molten material adds new oceanic crust to the ocean floor. 4. He formulated the theory of continental drift. 5. A rigid layer made up of the uppermost part of the mantle and the crust. 6. A break in the Earth's crust where masses of rock slip past each other. 7. _____ drift - The hypothesis that the continents drift slowly across the Earth's surface. 9. The layer of rock that forms Earth's outer surface. 13. ____ boundary - a plate boundary where two plates move toward each other. 15. _____ boundary - A plate boundary where two plates move away from each other. 16. A deep valley where two plates move apart. 18. The name of the single landmass that broke apart 200 million years ago and became the continents. 20. A section of lithosphere that carries pieces of continental and oceanic crust. 21. A device that determines the distance of an object under water by recording echoes of sound waves.