1. Section One Volcanoes and Plate Tectonics
Chapter 18 Volcanoes
Section One
Volcanoes and Plate Tectonics

2. Vocabulary Volcano: Magma: Island Arc:
A weak spot in the crust where magma has come to the surface.
Magma:
The molten mixture of rock-forming substances, gases, and water from the mantle.
Island Arc:
A string of islands formed by the volcanoes along a deep ocean trench.

3. Vocabulary Lava: Ring of Fire: Hot Spot:
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.
Hot Spot:
An area where magma from deep within the mantle melts through the crust above it.

4. Location of Volcanoes

5. Location of Volcanoes
Complete the concept map.
occur at

6. Location of Volcanoes Mid-Ocean Ridge

7. Volcanoes at Diverging Plate Boundaries
Describe how volcanoes form along the mid-ocean ridge.
Volcanoes form when lava pours out of cracks in the ocean floor.
True or False: Most volcanoes of the mid-ocean ridge rise above the ocean’s surface.

8. Volcanoes at Converging Boundaries
True or False: Many volcanoes form near converging plate boundaries where oceanic crust returns to the mantle.
How does subduction at converging plate boundaries lead to the formation of volcanoes?
Subduction causes slabs of oceanic crust to sink through a deep-ocean trench into the mantle, where it forms magma that rises back toward the surface. When the magma erupts, volcanoes are formed.

9. Volcanoes at Converging Boundaries
What are three major island arcs?
Three major island arcs include Japan, New Zealand, Indonesia, the Caribbean Islands, the Philippines, and the Aleutians.

10. Hot spot Volcanoes How did the Hawaiian Islands from?
The Hawaiian Islands formed as the Pacific plate drifted over a hot spot.
True or False: Hot spots form only under oceanic crust.