Inside Earth: Chapter 3- Volcanoes

1. Inside Earth: Chapter 3- Volcanoes Section 1: Volcanoes and Plate Tectonics

2. What is a volcano? • Volcano - weak spot in the crust where molten material, or magma, comes to the surface • Magma- molten mixture of rock, gasses, and water from the mantle • Lava- magma that reaches the surface

3. Location of volcanoes • There are about 600 active volcanoes on land. Many more lie below the sea. • Ring of Fire:a major volcanic belt formed by many volcanoes at the rim of the Pacific Ocean • Most volcanoes occur along diverging plate boundaries, such as the mid-ocean ridge or in subduction zones around the edges of oceans

4. Volcanoes at Diverging Plate Boundaries • Volcanoes form along the mid-ocean ridge, which marks a diverging plate boundary. Most of this is located underwater, except for places such as Iceland and the Azores Islands in the Atlantic Ocean.

5. Volcanoes at Converging Boundaries • Many volcanoes form near the plate boundaries where the oceanic crust returns to the mantle (subduction) • Subduction causes ocean crust to sink into the mantle forming a trench. • The crust melts and forms magma, which then rises back towards the surface.

6. Many volcanoes occur on islands, near boundaries where two plate collide. The resulting volcanoes create a string of islands called an island arc.

7. Hot Spot Volcanoes • Some volcanoes result from “hot spots” in Earth’s mantle. A hot spot is a weak spot where magma from deep in the mantle melts through the crust like a blow torch. • Hot spots often lie in the middle of continental or oceanic plates far away from plate boundaries.

8. Can gradually form a series of volcanic islands, for example the Hawaiian Islands, which formed one by one over millions of years as the Pacific plate drifted over a hot spot.

9. They can also form under the continents. An example of this is Yellowstone National Park in Wyoming, which marks a major hot spot under the North American plate.