Untitled Document
 Watch out! It's very hot!
And the mountain looks very angry! Fire balls can be seen coming out
of the top of the mountain! What is happening? Don't be scared. The mountain is
not angry. You are just watching a volcano! Did you know that
more than 80 percent of the Earth's surface was made from volcanoes?
And that the sea floor and mountains were
formed by countless volcanic eruptions, while the gases
released from volcanoes formed
the earth's atmosphere? So, what is a
volcano? This week, let's learn all about amazing volcanoes!
What Is a Volcano?
 Deep
inside the Earth, there is a solid mass of rock called the mantle. When rock from the
mantle melts and moves to the surface
through the earth's crust and releases built-up gases, volcanoes
erupt. But why does this
solid rock have to melt and come to the surface? Very high temperatures and pressure causes the rock
to melt and become liquid rock called magma. Magma is molten rock within the Earth's
crust. When magma erupts through the earth's surface, it is called
lava. Lava can be thick and slow-moving or thin and fast-moving. Most volcanoes
occur on plate boundaries. They can
also occur in areas where Earth's shifting plates meet, split apart, or slide against each other,
going in opposite directions. Volcanic eruptions
can cause great damage and the loss of life
and property.
Where Does the Word Volcano Come From?
The word volcano comes from the Roman god of fire, Vulcan불카누스.
Vulcan was said to have had a forge (a place to melt and
shape iron) on Vulcano. Vulcano
is an active volcano on the Lipari
Islands of Italy.
How Many Active Volcanoes Are There?
There are more than 500 active volcanoes in the world! More than half
of these volcanoes are part of the "Ring of Fire환태평양화산대,"
which is the area that circles the Pacific Ocean태평양.
Volcano eruptions can be very dangerous for people. They can kill
people and destroy their houses. Isn't it scary? But don't worry.
These days, volcano experts can see the sign of an eruption before
it happens. So they can warn people to move to safer
places.
 What
Are the Signs of an Eruption?
Before an eruption, the magma moves into the area beneath a volcano and collects
in a magma chamber. As it comes
closer to the surface, the magma releases gases. The gases tell us
that an eruption is going to happen soon. The movement of magma creates
small earthquakes and minor shakings, too. So when you
see gases coming out of the mountain top and feel small shakings,
run away!
What Is the Largest Volcano in the World?
The largest volcano on Earth is Hawaii's Mauna Loa. Mauna Loa is about
10 kilometers tall from the sea floor to its summit. It rises about 4
kilometers above sea level. But the most active
volcano in the U.S. is Mt. St. Helens. It is located in western Washington
State. The largest volcano in our Solar System is perhaps Olympus
Mons on the planet Mars. This huge volcano is 27 kilometers tall and
over 520 kilometers across! |
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