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Across 1. A deep valley along the ocean floor beneath which ocean crust slowly sinks toward the mantle. 4. While it was not the only supercontinent to exist, it was probably the most recent one. 6. He "stood on the shoulders of giants" and put together the theory of plate tectonics. 8. The scale most commonly used for measuring earthquakes today. 9. They gave Wegener one of the key pieces of evidence for his theory. 11. The most dangerous type of volcanic eruption. 12. It is thought to be the most geologically active area on Earth! 14. He was sure the continent moved, but could not prove it! 15. Old Faithful is one! 17. The supervolcano that is Yellowstone National Park has formed one of these. 18. This results when a piece of ocean crust is subducted back into the mantle. 20. A piece of the crust. 22. We can see an old one in around Seattle, Washington. NOT a good thing!

Down 2. There are only a hundred or so of them naturally occurring in the universe yet they combine to form countless types of matter. 3. They provide the energy which keeps the parts of the Earth in motion. 5. It made the loudest noise that has ever been recorded! 7. This can be affected by both temperature and the level of silica in lava. 10. In areas where the soil is very moist, an earthquake could cause this process to happen resulting in landslides and buildings sliding off of their foundations. 11. These islands were formed by volcanoes, and are referred to as an island arc. 13. While in the Navy, he discovered sea-floor spreading which explains how the continents move. 16. While this country is no longer over a geological hot spot, the number of batholiths and dome mountains there indicate that at one time there were many active volcanoes or fissures. 19. This volcano caused "the year we had no summer". 21. Although it is the smallest particle expelled from a volcano, it ultimately can do the most damage.