March 21, 2006
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Kanaga Volcano in Alaska
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 mVolcanic Island Clipartolten 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:

Black and White Clipart of a VolcanoWhere 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.

clipart of volcanoAnd 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.

Read more about plates. Watch a video about plates.

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.

Photo of a Smoking VolcanoCan 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

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!

There is an active volcano in the Pacific Northwest!!!

Mount St HelensOn 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.

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.

Spewing Colcano clipartBesides 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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