Volcano Information Center

A volcano is an opening in the earth’s crust which allows molten lava, gas, or ash to escape. Eruptions can cause lava flows, mudslides, avalanches, and falling ash. Volcanoes look like mountains, but they are really land that has been pushed upward by pressure beneath the surface.

The earth is made up of several layers. The top layer is the crust. The next layer is the mantle and mostly consists of rock. The innermost part of the earth is the core, and it is this inner layer that contains boiling gases and magma.

Volcanoes are classified as active or inactive. Scientists usually consider a volcano active if it is erupting, or if it is exhibiting signs of unrest. Signs of unrest include earthquakes or new gas emissions. Volcanoes sometimes remain inactive for thousands of years between eruptions. Inactive volcanoes can be seen during escorted tours to Costa Rica and Iceland.

There are over 400 active volcanoes on Earth. One third of all eruptions take place in Iceland. Volcanoes can be dangerous, but they are not the most dangerous of natural disasters. In the last 200 years, there have been over 200,000 deaths in volcanic eruptions.

General information on Volcanoes

• Cascades Volcano Observatory offers an overview on volcanoes.
• View a volcano photo gallery from National Geographic.
• Types of volcanoes
• How volcanoes work
• Volcano statistics
• Geography 4 Kids offers an explanation of the types of volcanoes.
• Utah Geographical Survey demonstrates the three main types of volcanoes.
• Volcano quiz

Volcanic Hazards

• Learn about volcanic hazards.
• The U.S. Geological Survey offers a fact sheet on volcanic hazards.

Volcaniclastic Names

• Vocabulary related to volcaniclastic particles.

Volcanic Eruptions and flows

• The Smithsonian Museum of Natural History offers information on erupting volcanoes.
• Pyroclastic Flows
• Pyroclastic Fallout
• Lahars
• More on lahars
• Debris-flow Avalanches

Volcanic Gases

• Volcanic gases and their effects

Volcano Forms and facts

• Volcano formation
• U.S. Search and Rescue Task force offers an overview on volcanoes and their formation.
• Volcaniclastic Sedimentation and Facies
• Volcanic lightning photos
• Volcanoes under glaciers

For further information

• U.S. Geological Survey
• NASA’s research on volcanoes
• Earth’s active volcanoes from Michigan Tech
• Italian volcanoes
• Bentonites and Tonsteins
• State geological surveys
• FAQ about volcanoes and volcanologists
• World Wide Earth Sciences Organizations
• Geosciences Departments of the U.S. and Canada
• World Organization of Volcano Observatories (WOVO)
• National Geologic Maps Database

Forecasting Eruptions

Can volcanic eruptions be predicted? As magma moves into the area below the volcano, it collects in a reservoir. As it moves closer to the surface, gases are emitted. The movement of magna produces small earthquakes, which can be measured by seismographs. Magma in the reservoir may cause swelling of the volcano’s slopes. The swelling can be measured with tools known as tiltmeters and geodimeters.

Each volcano is unique. Events that precede an eruption at one volcano may not occur at another volcano. The science of monitoring volcanoes is still growing. Research is continually being done to improve forecasting of volcanoes and reduce the number of lives that are lost.