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What is a volcano?
A volcano is a weak spot in the crust where molten material, or magma, comes to the surface. Magma is a molten mixture of rock-forming substances, gases, and water from the mantle. When magma reaches the surface, it is called lava.
How are volcanoes formed?
Deep in the earth, it is very hot. It is so hot that rocks melt. The melted rock is called magma. The magma is lighter than the rocks around it so it rises. Sometimes it finds a crack or hole in the earth’s crust and bursts through. This is how a volcano begins.
Where are volcanoes located?
Volcanic belts form along the boundaries of Earth's plates. One major volcanic belt is the Ring of Fire, formed by the many volcanoes that rim the Pacific Ocean. Volcanoes form along mid-ocean ridges, which mark diverging plate boundaries. Volcanoes also form along diverging plate boundaries on land. Many volcanoes form near converging plate boundaries where oceanic plates return to the mantle.
What are hot spots?
A hot spot is an area where material from deep within the mantle rises and then melts, forming magma. A volcano forms above a hot spot when magma erupts through the crust and reaches the surface. The Hawaiian Islands were formed from a hot spot in the Pacific Plate.
Hot springs and geysers are types of geothermal activity that are often found in areas of present or past volcanic activity. A hot spring is formed when groundwater is heated by a nearby body of magma or by hot rock deep underground. A geyser is a fountain of water and steam that erupts from the ground.
Inside a Volcano
Magma collects in a pocket called a magma chamber beneath a volcano. The magma moves upward through a pipe, a long tube in the ground that connects the magma chamber to Earth's surface. Molten rock and gas leave the volcano through an opening called a vent. Often, there is one central vent at the top of a volcano. However, many volcanoes have other vents that open on the volcano's sides. A lava flow is the area covered by lava as it pours out of a vent. A crater is a bowl-shaped area that may form at the top of the volcano around the central vent.
Why do volcanoes erupt?
Pressure builds deep in the earth where the magma is. Suddenly the gases escape and violently explode. It is kind of like toothpaste squirting out of a tube when you give it a hard squeeze. Geologists classify volcanic eruptions as quiet or explosive. A pyroclastic flow occurs when an earthquake eruption hurls out a mixture of hot gases, ash, cinders, and bombs. Geologists often use the terms active, dormant, or extinct to describe a volcano's stage of activity. An active, or live, volcano is one that is erupting or has shown signs that it may erupt in the near future. Scientists expect a dormant volcano to awaken in the future and become active. An extinct, or dead, volcano is unlikely to erupt again.
What are the different kinds of volcanoes?
Volcanoes do not all look alike. Their shape is based on what type of materials they erupt. There are three main kinds, or shapes, of volcanoes. They are shield volcanoes, cinder cone volcanoes, and composite volcanoes. A caldera is the huge hole left by the collapse of a volcanic mountain.
Volcanoes that build up from
many slow, steady, flows of hot lava, are called shield volcanoes. This kind of volcano is low and broad with gently sloping sides. They look like a warriors shield.
Cinder cone volcanoes form when solid rock and ash shoot up into the air and fall back around the volcano opening. The cinder cone volcano has steeply sloped sides that wear away easily.
Composite volcanoes erupt with molten lava, solid rock, and ash. The layers pile up much like layers of cake and frosting. The layers form into symmetrical cones, and the slopes are steep and do not wear away quickly.
There is much more about volcanoes out there. Look in books and on the internet . Have Fun!
Pictures, Images, and information From:
Soames Summerhays/Photo Researchers, Inc.
Kraft-Explorer/Photo Researchers Inc.
Masao Hayashi-Dung/Photo Researchers Inc.
Why Do Volcanoes Blow Their Tops? By Melvin and Gilda Berger
Inside Earth by Prentice Hall
é igneous – having to do with fire
é magma – melted rock under the ground
é lava – melted rock on top of the ground
é volcano – one kind of mountain
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