Download Getting to Know: Volcanoes

Getting to Know: Volcanoes
In AD 79, the volcano Mount Vesuvius erupted. It
destroyed the nearby city of Pompeii. In a very short time,
the city was covered 9 feet deep in ash and other volcanic
material.
You might have heard of Pompeii. But did you know that
Mount Vesuvius is still active? That means it can still erupt,
any time! In fact, it has erupted twice in the past 100 years.
It erupted in 1906 and in 1944.
There is something even more surprising than that! Many
people live near this active volcano. Orchards are planted
on its slopes. Grapevines grow there, too. The soil left after
a volcano erupts can be great for growing crops.
You might think you know a lot about volcanoes. But they
may surprise you.
What is a volcano?
A volcano is a hole or crack in Earth’s crust. At a volcano,
molten rock from below Earth’s surface can seep through.
You might remember that under Earth’s crust, there is a
layer of molten rock. This molten rock is part of a layer
called the mantle. When a volcano erupts, some of the
mantle comes through the crust.
The eruption of Mt.Vesuvius
covered the nearby city of
Pompeii in ash.
An eruption can be slow, like molten rock bubbling up through the crust. Other eruptions
can be fast and powerful, spewing ash, hot gases, and rock in all directions.
Misconception 1: Volcanoes are mostly found in hot climates.
Actually, volcanoes are found in all kinds of climates. Some volcanoes, like Alaska’s
Redoubt volcano, erupt through layers of ice and snow!
Concept: Volcanoes
Getting to Know
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Why do volcanoes erupt in the first place?
Under Earth’s crust, temperatures are very hot. Rock
deep within Earth becomes so hot that it changes
from a solid to a liquid. Because liquid rock is less
dense than solid rock, it collects in a layer just under
Earth’s hard surface. The melted rock is called magma.
Where there are cracks and holes in Earth’s crust, the
magma can flow through. If the magma is thick, it may
flow out slowly. If the magma is thin, it may allow hot
gases to escape in an explosion.
This map shows active volcanoes
as well as volcanoes that were active
not long ago.
Most volcanoes are near the edges of Earth’s tectonic
plates. This is because there are more cracks and holes
in Earth’s crust in those places.
So, volcanoes are only found near the
edges of Earth’s plates?
Well, no, most volcanoes are found near the edges. But there are other areas, sometimes called “hot spots,” where volcanoes form. The volcanoes that formed the Hawaiian Islands are on one of these hot spots. Wait a second! Volcanoes made the
Hawaiian Islands?
Plumeria is just one tropical
It’s true! In fact, the main island, Hawaii, is made up of
flower that thrives on volcanic
five volcanoes. Kilauea, one of these, is the most active
Hawaii.
volcano on Earth today. When you think of Hawaii, you
might think of beautiful beaches and lush forests. You
might think of tropical birds and beautiful flowers. It might seem strange to think that an area
with so many volcanoes is so full of life. But that is just one of the many ways volcanoes can
surprise you.
Misconception 2: Volcanoes are only found on land.
Volcanoes can happen on land or on the ocean floor. When volcanoes erupt under the
ocean, they form underwater mountains. Sometimes these get so tall that they rise
above the surface of the water. The Hawaiian Islands were formed this way.
Concept: Volcanoes
Getting to Know
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.