1. Islands formed where plates coverge and one plate subducts under another . 2. A deep , underwater trough is formed when one plate is forced under another .

3. The plates move horizontally , but the crust also can move vertically .

4. These emerge as islands about 100 km away from the plate boundary .

5. These forms slowly and in stages over millions of years .

6. These are the deepest places in Earth’s oceans .

7. One of these contains most of the volcanoes in the United States .

8. These can be produced by a collision between two continental plates .