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Across 1. A change in the Earth's magnetic field 5. 2 plates sliding back and fourth against each other 6. very hot, very dense center of our planet. 8. an elastic wave in the earth produced by an earthquake or other means. 10. hard outer layer of Earth 11. 2 plates pushing together 12. pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. 13. the formation of new areas of oceanic crust, which occurs through the upwelling of magma at mid ocean ridges and its subsequent outward movement on either side. 14. includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth 15. thick layer of hot, solid rock between the Earth's crust and the molten iron core 16. 2 plates pulling apart 18. when one tectonic plate shifts under another

Down 2. the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur. 3. a current in a fluid that results from convection 4. hypothetical supercontinent that included all current land masses 7. the part of the Earth's mantle below the lithosphere and the asthenosphere, but above the outer core 9. the gradual movement of the continents across the earth's surface through geological time 17. be broken by a fault or faults