NSSS3.1


 * toc**

=3.1 Volcanoes and Plate Tectonics=

Vocabulary

 * Volcano**: A weak spot in the crust where molten material, or magma, comes to the surface.
 * Magma**: A molten mixture of rock - forming substances, gases, and water from the mantle.
 * Lava**: Magma that reaches the surface, it is called lava.
 * Ring of Fire**: The many volcanoes that rim the Pacific Ocean.
 * Island Arc**: The resulting volcanoes create a string of islands called an island arc.
 * Hot Spot**: An area where magma from deep within the mantle melts through the crust like a blow torch.

**What is a Volcano**

 * Volcanic activity is a constructive force instead of a destructive force because when lava, magma on the surface, cools down it adds new rock

Location of Volcanoes

 * On land, there are over 600 volcanoes which are active
 * In the sea, there are many more active volcanoes
 * Along the boundaries of the Earth's plates, volcanic belts are formed
 * The most famous one is the //Ring of Fire//, a volcanic belt which is around the Pacific Plate
 * Many volcanoes occur divergent boundaries or subduction zones

Volcanoes at Diverging Plate **Boundaries**

 * At the mid-ocean ridge, many volcanoes form
 * In a few places, volcanoes which occur there rise to the surface

Volcanoes at Converging Boundaries

 * Many volcanoes occur on islands, near where an ocean-ocean plate collision happened
 * When these volcanoes happen in a string, they create an island arc

Hot Spot Volcanoes

 * In the middle of continental and oceanic plates, "hot spots'' are there
 * Gradually hot spot volcanoes form a chain of volcanic mountains
 * Ex. the Hawaiian Islands