Volcanism Volcanoes A mountain built from magma Can

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