What is a Volcano?
- A volcano is a vent, or opening, in
the earth's crust where melted rock (molten rock) called magma
is ejected. We also use the word "volcano" to
- describe the mountain that is built
up by the m
 olten
rock and ashes.
- Photograph by E. Klett on 27 January
1994;U.S. Fish and Wildlife Service
How are Volcanoes formed?
The temperature deep inside the earth is so hot it melts rock
into a super-hot liquid called magma. It also builds up a lot of pressure.
This pressure pushes the magma, along with gases and steam, up through
openings in the earth's crust. Parts
of a Volcano
-
Volcanoes occur
in two different places on Earth:
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 Where
plates of the Earth's crust
meet and rub together or where plates are moving apart.
This is how volcanoes
like Mount St. Helens were formed. A volcano
forms when magma (molten rock) from inside the Earth is forced
up through the surface. The molten rock comes out of the top
of the volcano and flows downward over the earth. (When magma,
or molten rock, comes out of a volcano we call it lava. Helps
to keep track of where the molten rock is … inside the earth
or flowing down the side of a volcano.) Slowly the lava cools
and hardens into rock. Every time the volcano erupts,
more lava flows downward until layer upon layer of rock is formed.
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 And
the second is the
middle of the Earth's plates,
right above a source of magma. Magma (molten rock) rises up
to the surface from deep inside the Earth and erupts like
a blowtorch. Hotspots like this stay in one place, while the
plates of the Earth keep moving.
Over thousands of years hotspots
like these form strings of volcanic islands in the ocean.
This was how the Hawaiian Islands were formed. Another kind
of hotspot creates geysers.
Some of the most famous hotspots
found inland are the geysers at Yellowstone
National Park - although there is no lava flowing from
the geysers, the water and steam that burst through the cracks
in the Earth's crust are believed to be heated from magma
deep inside the earth.
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- Inside the Earth:
If you could tunnel to the center of the Earth you
would find that the Earth is made up of many different layers:
-
The Crust
- this is the layer we live on and scientists think it is about
25 miles thick under the continents and about 3-5 miles thick
under the oceans. It is made up of topsoil and layers of hard
rock.
-
The Mantle
is about 1800 miles thick and is made of very hot, packed rock
that is so hot that the rocks melt, forming magma. The magma in
the mantle causes the earth's plates to move.
The Outer
Core
The outer core is made up of melted metals like nickel and iron
and molten rock. It is believed to be between 1400 and 1500 miles
thick.
The Inner
Core of the Earth is 750-800 miles thick and although
no one has measured the temperatures of the Inner core it is estimated
that the temperature is between 3000 and 10,000 degrees!! Talk
about HOT! The inner core is made up of liquid metals like nickel
and iron and the pressure on the inner core squeezes the hot liquid
metals so much that it can't move around like a liquid but is
forced to stay in place like a solid ball.
 Are
There Different Types of Volcanoes?
Yes there are many different types of Volcanoes! Check out Volcano
World for complete descriptions of the different types of volcanoes.
The "U.S.
Geological Survey also has great definitions of the different
types of volcanoes and other volcano terminology!
What is Lava?
Magma
which has reached the surface of the earth through a volcanic eruption
is called lava.
There are 2 kinds of lava: pahoehoe,
which is smooth, billowy, or ropey and 'a'a,
which is stiff, rough and jagged. This Hawaiian name means "
a painful surface for walking." Watch this video.
  Can
we Predict Volcanoes?
Scientists are becoming more
and more skilled at spotting the warning signs of an eruption.
They use clues about past eruptions by studying the deposits left
behind. Go
behind the scenes to find out what other efforts are being made to
predict
volcanoes.
- Did you
know that there are volcanoes on other planets?
There
is evidence that there was volcanic activity on the moon, Mars,
Venus and IO. The largest volcano on Mars is three times as high
as the biggest Earth volcanoes. However they are extinct.
Read about Volcanoes
on Mars or Volcanoes
of Other Worlds
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Are There
Volcanoes in Idaho?
Well
there aren't any active volcanoes right now but there is plenty
of evidence of several different types of volcanoes in Idaho:
Check out the volcanic history of Idaho at the USGS
site!
Check out
some of the history of The
Craters of the Moon. The National
Park Service also has great info about the Craters of the
Moon national park ... including resources for teachers and
an area designed just for kids!
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There
is an active volcano in the Pacific Northwest!!!
 On
May 18, 1980 Mount St Helens, a volcanic mountain in the Cascade
Range of Washington, erupted and has remained active since.
Read the true story of Mount
St Helen's.
Did you
know that Mount St. Helens has been an active volcano for much
of its more than 40,000 years of existence. Native Americans
living nearby named it Louwala-Clough, which translates into
"smoking mountain." Mount St. Helens received its
present name in 1792 from Captain George Vancouver, who was
exploring the Pacific Northwest for the British.
All
about Mount St Helen's from USGS. Mount
Saint Helen's Volcano
Cam
The USGS
estimates that the Pacific Northwest has at least 12 volcanoes
that could become active. These include Mt. Rainier, outside
of Washington; Mt. Hood, near the Columbia River in Oregon;
and Mount Shasta, in northern California.
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For people living
close to a volcano it is important that you have a plan in case the
volcano becomes active. Check out Planning
for Disaster to see how the people near Rabaul volcano on the
Papua New Guinean island of New Britain saved themselves.
 Besides
landslides, lava flows and ash, what are some of the other volcanic
hazards?
Here is a list
of the items suggested for your own Disaster
Supply Kit for emergency situations like erupting volcanoes.
There
is a lot to learn about volcanoes! Have fun exploring!
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