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Volcanoes and Plate Tectonics
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Vocabulary
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 * Volcano**: a weak spot on our planet's surface where molten material, or magma, comes to the crust
 * Magma**: a molten mixture of rock-forming substances, gases, and water from the mantle
 * Lava**: liquid magma that reaches the surface; also the rock formed when liquid lava hardens
 * Ring of Fire**: a major belt of volcanoes that rims the Pacific Ocean
 * Island Arc**: a string of islands formed by the volcanoes along a deep ocean trench
 * Hot Spot**: an area where magma from deep within the mantle melts through the crust above it

Outline
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What is a Volcano ?

 * Magma comes to the surface, when it reaches the surface it's called magma
 * After lava cools it turns into solid rock
 * The lava released builds up Earth's surface

Location of Volcanoes

 * one major volcano belt is the **Ring of Fire**
 * most volcano belts form along plate boundaries
 * At plate boundaries, huge pieces of the crust **diverge** ( pull apart) or **converge** (push together)
 * hear the crust is too weak that the magma can easily get through

Volcanoes at Diverging Plate Boundaries

 * volcanoes form along the **mid-ocean ridge**
 * along the ridge lava pours out of cracks into the ocean floor
 * In very few places like, Iceland and Azores Islands in the **Atlantic Ocean**, the volcanoes of the **mid-ocean ridge** rise above the ocean's surface

Volcanoes at Converging Boundaries

 * many volcanoes occur on islands or near boundaries where two oceanic plates collide
 * the older, denser plate dives under the other plate creating a **Deep-ocean trench**

Hot Spot Volcanoes
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 * hot spots often lie in the middle of Continental or oceanic plates for from any plate boundaries
 * Hot spots can also form under continents
 * There is a major hot spot under the North American Plate at Yellowstone National Park in Wyomin