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volcanoes

OLogy Series
geology
card
250

volcanoes

OLogy Series
geology

Some volcanoes erupt explosively, like opening a shaken soda bottle, because their magma is full of gases. Other volcanoes erupt gently, like boiling milk spilling over the sides of a pot, because their magma has fewer gases. An "active" volcano erupted recently or might erupt soon. A "dormant" or sleeping volcano has been quiet for a long time, but may erupt again someday. An "extinct" volcano has not erupted for over 10,000 years.

The hot, liquid rock that erupts from a volcano is called:

magma

lava

mantle

Are you right?

Correct!

Magma is melted rock that forms deep below the Earth's surface in the crust or mantle. Magma is pushed up through the crust in a volcanic eruption. When it reaches the surface, it's called lava. Lava flows over the Earth's surface and cools to form igneous rock.

Volcanoes are found:

in the middle of tectonic plates

near the boundariese of tectonic plates

both

Are you right?

Correct!

Most volcanoes are found where tectonic plates meet. The most explosive ones occur where one plate moves under another. But volcanoes can also occur in the middle of plates over hot spots, areas of intense heat deep below the Earth's crust.

When volcanoes erupt, they often bring rocks and minerals from deep within the Earth to its surface. These volcanic materials can include:

gold

silver

diamonds

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Correct!

Diamonds form miles below the Earth's surface, where extreme pressure causes carbon atoms to crystallize into diamond. When a volcano erupts, the diamonds are carried to the surface in volcanic rocks.

Jim Webster, Earth scientist

The most exciting thing that I have ever done was to walk across a fresh, hot lava flow in Hawaii. Its hot surface had hardened just before my boots touched it!

Volcanic eruptions helped form the Earth's atmosphere and the air we breathe.

Fact
or
Fiction
?

Fact

Early in the Earth's history, gases like water vapor released during volcanic eruptions formed the planet's earliest atmosphere.

Volcanoes are found on every continent except Antarctica.

Fact
or
Fiction
?

Fiction

Volcanoes are found on Antarctica, too. In fact, a new volcano was just discovered off the coast of Antarctica.

Definition: a crack in the Earth's crust where magma rises from below the Earth's surface
Materials released: lava, gases, ash, rocks, and minerals
Types: active, dormant, extinct
Frequency of eruption: On land, about 50 to 70 volcanoes erupt each year.
No. of active named volcanoes: about 1550
Cool fact: Most magma erupts underwater.

Image credits: courtesy of USGS; Jim Webster: courtesy of AMNH.