Volcanic Activity. Silica Earth’s crust and mantle are mostly made of silica The more silica in the magma, the thicker it is.

Volcanic Activity

Silica

Earth’s crust and mantle are mostly made of silica

The more silica in the magma, the thicker it is

SilicaMagma with a lot of silica makes light-colored lava that is very thick

When high silica lava cools, it makes rocks like rhyolite, pumice and obsidian

SilicaMagma that does not have much silica moves quickly and is thin.

Low silica magma is dark colored and makes rocks like basalt

Types of Volcanic Eruptions

The amount of silica determines if an eruption is quiet or explosive

Quiet Eruptions

Quiet eruptions are when magma flows out easily from the vent and volcano sides.

Quiet eruptions produce two types of lava

Quiet Eruptions

Two types of lava

Pahoehoe is fast- moving, hot, thin lava

Quiet Eruptions Aa lava is cooler and slower

moving. It hardens to form rough, jagged rocks.

Explosive Eruptions

If magma is thick, the eruption is explosive.

The magma builds up and plugs the pipe, building pressure.

The erupting gases push the magma out quickly.

Explosive Eruptions

The force of the explosion splits the lava into several pieces.

Ash are smallest pieces

Cinder are pebble-sized particles.

Explosive Eruptions

Bombs are larger pieces (baseball to car)

Explosive Eruptions

Pyroclastic flow is when an eruption spews out ash, cinders, bombs, and gases.

Stages of a Volcano

There are three stages of a volcano

Active: The volcano is erupting or may erupt in near future

Dormant: The volcano is sleeping and may awake in the future.

Stages of a Volcano

Extinct: The volcano is unlikely to erupt again.

Other Types of Volcanic Activity

Hot springs form when water around the volcano is heated by magma.

Geysers are created when this hot water gets trapped under ground and builds pressure until it erupts.

GEYSER

Geothermal Energy

Geothermal energy uses water heated naturally by magma to create energy.

Steam spins the turbines which turns a generator to make electricity.

Monitoring Volcanoes

We are getting better at predicting volcanoes.

Many small earthquakes around a volcano are common before an eruption.

Volcano Hazards

People are dormant volcanoes can be caught by surprise.

Quiet eruptions are dangerous because the lava sets fire to everything.

Volcano Hazards

Explosive eruptions are dangerous because of volcanic gases as well as flying lava.

Eruptions can cause landslides and avalanches.