Volcanoes

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Magma Chamber

SideVent

VentCrater

Pipe

Hot SpotsHot Spots

• Hot spots are caused from pockets of magma that raise up through openings in the crust.

• While the plate moves the magma oozes out, cools, and makes new layers on top of other layers.

• When these layers raise up above the level of the ocean they make islands, for example like the Hawaiian islands.

Ring of Fire

• Ring of Fire are volcanoes that are located on the edges of the Pacific plate that happen to make a rough ring of volcanoes.

• Ring of fire is where most of the active volcanoes are located.

Styles of EruptionsStyles of Eruptions

• Eruptions could be either explosive and violent or soft and quiet.

• Explosive volcanoes act like a soda can that has been shaken up.

– Trapped gases like water vapor and CO2 are in the magma and build up pressure until the magma nears the surface and the gases escape all at once forcefully.

Magma Composition & Composition & Water Content Content

• Magma that is low in silica is very liquidy and makes quiet eruptions (EX: Kilauea in Hawaii)– This lava pours out from sides of volcanoes

called vents. It also pours out from rift zones which are long deep cracks like in Iceland.

• Magma with lots of silica make very violent, explosive eruptions (EX: Mount St. Helens in Washington)

Forms of VolcanoesForms of Volcanoes

Shield Volcano

– Quiet eruptions spread out silica poor lave in flat layers.

– Have gentle sloping sides.

– Looks like a shield laying down.

Forms of Volcanoes

• Composite Volcano

– Some volcanoes can be either explosive or quiet. When a volcano erupts explosively then erupt quietly the next time, it makes different layers of tephra and cinders which is why it is called a composite volcano.

– Mount St. Helens is a composite volcano because the Juan de Fuca plate was forced below the North American plate which caused eruptions to be explosive then quiet at different times.