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Volcanoes

What is a Volcano? A volcano is an opening in the Earth where hot, liquid rock, called magma, bursts out.

Types of Volcanoes

Fissure Volcano A fissure is a crack in the Earth's crust. It can measure many miles long. Magma erupts through the fissure and flows down the sides of the volcano in little rivers, to form a gentle slope on each side.

Shield Volcano Volcanoes in the Hawaiian Islands in the Pacific Ocean have runny lava. This lava flows out gently to form a shallow volcanic cone shaped like a shield.

Dome Volcano A dome volcano has a single vent, or pipe, from which the magma erupts. Thick, fast-cooling lava flows down the sides of the volcano to form a steep-sided dome.

Ash-Cinder Volcano When a volcano erupts, the heavy cinders fall on the sides of the volcano first, followed by the lighter ash. After each eruption, layers of cinders and ash build to form a steep-sided cone.

Caldera Volcano When the top of a volcano collapses into the magma chamber, it makes a crater, or caldera. Sometimes this fills with water to form a lake.

Composite Volcano A composite volcano is formed of layers of ash and lava in the same way as an ash-cinder volcano. The sides are steep.

Major Eruptions Every year at least 60 volcanoes erupt somewhere in the world. Many eruptions are small, but some are huge and cause great damage. The eruption of Vesuvius, in Italy, buried the town of Pompeii in hot ash and cinders. People in nearby Herculaneum were also killed in the blast of hot ash and gas.

Famous volcanic eruptions

Krakatau, 1883 A volcano blew this island in Indonesia to pieces. People heard the explosion 2,480 miles away, and the ash in the sky made the moon and sun look green.

Katmai, 1912 When mount Katmai, in Alaska, exploded, a huge area was covered in a thick layer of ash. Luckily, not many people were killed, as only a few lived nearby.

Pinatubo, 1991 Mount Pinatubo, in the Philippines, erupted after 600 years. The huge clouds of ash and dust blocked out the sun and buried villages and fields for miles around.

Vesuvius, A.D.79 The eruption of Vesuvius is probably the most famous volcanic explosion ever. The remains of the people killed in a huge blast lay undiscovered for 1,700 years.

Volcanoes in Space

There are volcanoes on many of the moons and planets in our solar system. The Earth’s Moon has many volcanoes, and so does Mars, but all of these are now extinct. Venus, Jupiter, and possibly Uranus have active volcanoes. These volcanoes are usually large, and they erupt often and with great force. Jupiter’s volcanoes throw out sulphur instead of lava.

The eruption of Io

In 1979 the American spacecraft Voyager 1 flew past Io, one of the 16 moons of Jupiter. At the time, the volcano Prometheus was throwing out a fountain of gases 100 miles into space above the moon’s surface.

Record Breaker

The largest-ever volcano is not on Earth, but on the planet Mars. Olympus Mons is extinct and is 3 time taller than Mount Everest, the highest mountain on Earth.