1. Volcanoes and Plate Tectonics Chapter 6 Section 1

2. Key Terms  Volcano  Magma  Lava  Ring of Fire  Island arc  Hot spot

3. What is a Volcano?  Volcano: a weak spot in the crust where magma comes to the surface.  Magma: molten mixture of rock-forming substances, gases, and water from the mantle.  Lava: magma that reaches the surface.  https://www.youtube.com/watch?v=BAR3 P3Fshok https://www.youtube.com/watch?v=BAR3 P3Fshok

4. Volcanoes and Plate Boundaries  There are about 600 active volcanoes on land, and many more under the sea.  Ring of Fire: a major volcanic belt in the Pacific Ocean.  Volcanic belts form along the boundaries of Earth’s plates.  Most volcanoes form along spreading boundaries and such as mid-ocean ridges and along colliding boundaries where subduction takes place.

5. Check for Understanding  Approximately how many volcanoes are there above land?  How many do you think there are total including those on land and those under the sea?  What is the name of the major volcanic belt beneath the Pacific Ocean?

6. Who Am I?  I am a type of boundary. Volcanoes form along my mid-ocean ridges where there is lava in my rift valleys. Who am I?  I am a type of plate movement where one tectonic plate runs into another and slides underneath it. Who am I?  I am another type of boundary where subduction takes place. Who am I?

7. Spreading and Colliding Boundaries  Volcanoes form along the mid-ocean ridges where there is lava down in the rift valleys (spreading boundaries).  Volcanoes also form near colliding boundaries where oceanic plates return to the mantle.  During subduction, the plate going under the other plate melts and turns into magma. This magma rises upward, breaks through the ocean floor, and creates volcanoes.  The resulting volcanoes create a string of islands called an island arc.  https://www.youtube.com/watch?v=ryrXAGY1dmE https://www.youtube.com/watch?v=ryrXAGY1dmE

8. Hot Spot Volcanoes  Hot spot: an area where material from deep within the mantle rises and then melts, forming magma.  A volcano forms above a hot spot when magma erupts through the crust and reaches the surface.