1. Volcanism

2. Volcanoes A mountain built from magma
Can occur on land or in the ocean

3. Magma
Liquid rock

4. Volcanism
Any activity that includes the movement of magma toward or onto the surface of the earth.

5. Lava
Magma that erupts onto the earth’s surface

6. Vent
Opening through which the molten rock flows onto the surface

7. Volcanic Zones Located near tectonic plate boundaries
Most active volcanoes are found in zones near both convergent and divergent boundaries

8. Subduction Zones
Pacific Ring of Fire

9. Subduction Zone
Island arc

10. Mid-Oceanic Ridge
The greatest amount of magma comes to the surface at ridges
Mainly occur deep in the ocean
Exception is Iceland

11. Fissures
Large cracks that lava flow

12. Hot Spots
Areas that magma flow to the surface that are not at plate boundaries but occur at stationary areas in the Earth’s crust

13. Local Effects
Clouds of host ash, dust, and gases can flow down the slope of a volcano at speeds of up to 200 km/hr and sear everything in their path.

14. Local Effects
During an eruption, volcanic ash can mix with water and produce mudflow that runs downhill.

15. Local Effects
Ash that falls to the ground can cause buildings to collapse under its weight, bury crops, damage the engines of vehicles, and cause breathing difficulties.

16. Global Effects Change the Earth’s climate for several years
Clouds of volcanic ash and sulfur gas reach the upper atmosphere and reduce sunlight