Chp 18.3 Notes TYPES OF VOLCANOES &

WHERE THEY OCCUR

Main Idea 1: Not all volcanoes are built the same. A volcano’s shape is determined largely by:

1. magma’s viscosity 2. force of any eruptions 3. amount of weathering

Composite Volcano

Describe: Large, symmetric volcano with sharp peaks,& violent eruptions.

Magma: Very viscous

Eruption: Can be slow seeping or violent explosions.

Shield Volcano

Describe: have gradual slopes& peaceful eruptions

Magma: Not very viscous

Eruption: Travels a long distance.

Kilauea Shield Volcano

Cinder Cone Volcano

Describe: small volcano with steep slopes and a holeat top made of cinders

Caldera

Describe: A depression thatforms when a volcano collapseson itself.

Lava Dome

Describe: volcano that forms from very viscous magma atthe peak of another volcano. Lava domes can act like a cork and can eventually result in explosive pyroclasticflows.

Magma type:Very viscous (thick& resistant to Flow)

Mount St. Helens

Main Idea 2: Volcanoes occur in specific regions of Earth.

Subduction Zone Volcano:

Describe: where oceanic crust isPushing under continental crust.

Magma/Eruption: Very viscous& can lead to violent eruptions.

Examples: Ring of Fire aroundPacific Rim where magma comes rising from mantle.Mt. Pinatubo, AK Aleutian Chain are examples

Rift-Zone Volcano:Where 2 plates are diverging, spreadingapart, at an ocean ridgeor in the middle of a continent.

example: African RiftValley.

Hot Spot Volcano:Where magma rises througha thin portion of the crust.

Example: Most famousexample is Hawaiian Islands.the hot spot stays in sameplace & ocean crust keepsmoving, so there is a chain of islands.