3.5 Volcanoes

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3.5 Volcanoes

Learning objectives

After studying this section, you will be able to:

• Describe what happens during a volcanic eruption;
• Explain what the effects of volcanic eruptions are.

What do you know about volcanoes?

Types of volcanoes

Mount Merapi on Indonesia is a composite volcano.

The area around the shield volcano Katla in Iceland.

Escaping the pyroclastic flow

Lahar = Mudflows created of molten snow from the top of the volcano.

Crater

This path leads you to the top of the Vesuvius.

The slopes are very steep.

The city of Napels in Italy. People live close to the volcano. Do you know why? Look at 3.6 to see if your answer is in there.

This is the Vesuvius in Italy. The last eruption was in 1946. It is an example of a composite volcano.

Do you know who lives here?

Hot spots

A chain of volcanoes (hotspot track) forms as a tectonic plate moves over a plume of hot mantle material (hotspot) rising from deep within the Earth.

(Source: U.S. National Park Service)

Predicting a volcanic eruption

Volcanic eruptions are easier to predict than earthquakes. Volcano scientists monitor volcanoes for warning signs that a volcano will become active. Warning signs include small earthquakes, temperature increases around the volcano and the release of gas (sulphur) clouds.

In 2015, the Cotopaxi volcano in Ecuador was showing signs of increased activity, which led the Ecuadorian government to announce a state of emergency. Inhabitants of the town close to the volcano left and tourists cancelled their bookings. In the end the feared eruption did not occur, and the volcano calmed down a bit.

Essence

Volcanoes occur at divergent and subduction plate boundaries and hot spots. Hot spots are areas where the mantle is extra hot. During a volcanic eruption, the magma rises from the magma chamber through the main vent or side vents and exits the volcano. Besides lava, there can be ash, volcanic bombs, gas, or a combination (pyroclastic flow) exiting the volcano.

Go to the planner in Teams for the homework