Volcanism

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

Magma Liquid rock

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

Lava Magma that erupts onto the earth’s surface

Vent Opening through which the molten rock flows onto the surface

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

Subduction Zones Pacific Ring of Fire

Subduction Zone Island arc

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

Fissures Large cracks that lava flow

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

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.

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

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.

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