VOLCANOESBy Michael Keegan, 6W

WHAT IS A VOLCANO?• A volcano is usually a

mountain that liquid rock from the Earth, called lava, escapes from.

• A volcano is also an opening in the Earth’s surface where magma and hot gas can escape.

HOW ARE VOLCANOES FORMED?

• Volcanoes are formed when magma in the earths mantle forces its way up through thin weak layers of the earths crust.

STRUCTURE OF A VOLCANO• A volcano has a vent, a pipe, a crater, and

a cone.• Vent: the vent is the opening in the earth’s

surface.• Pipe: the pipe is a passageway where the

magma rises up through the volcano during an eruption.

• Crater: the crater is at the top of the volcano, which looks like a bowl shape, where material is released.

• Cone: layers of lava, ash and cinder which solidify around the edges of the volcano.

WHY DOES A VOLCANO ERUPT?

The Earth’s crust is made up of tectonic plates which all fit together like a jigsaw. These tectonic plates also move. When two tectonic plates

collide, one is pushed up onto the other and magma is

squeezed between the two.

PYROCLASTIC FLOWS• A pyroclastic flow is a

devastating type of volcanic eruption. It is made up of hot gas and rock which travel from the volcano at high speeds, usually faster than 700 kilometres an hour. These flows can get up to 1000°C. Pyroclastic flows run downhill and spread out under pressure.

CROSS SECTION OF A VOLCANO

TYPES OF VOLCANOES• Composite Volcanoes: are formed by

alternating layers of lava and rock fragments.

• Shield Volcanoes: these volcanoes are formed by many layers of running lava which make a cone-shape at the top.

• Cinder Volcanoes: are the most common form of volcanoes. They are built up from lava fragments called cinder.

• Complex Volcanoes: are volcanoes made up of many flows, ash layers, domes and cones with a more complicated system.

MAJOR ERUPTION• Mt Tambora on the Sumbawa Islands

in Indonesia is a 4,300 metre high volcano. Mt Tambora erupted in April

1815 and the volcanic eruption measured a 7 on the Volcanic

Explosivity Index. The explosion was heard even on Sumatra Island which is 2,000 kilometres away. The death

toll is thought to be over 71,000 people.

BIG VOLCANOES• The worlds tallest volcano is Hawaii’s

Mauna Kea which is 10,203 metres tall which is taller than Mount Everest.

• The largest volcano in volume is also located in Hawaii. Mauna Loa has a volume of 42,500 cubic kilometres.

• The largest volcano in the solar system is Olympus Mons on planet Mars which is 27 kilometres tall and 520 kilometres wide.

• There are more than 500 active volcanoes in the world, most in The Pacific Oceans Ring Of Fire.

• Magma is liquid rock inside a volcano, whilst when the liquid rock is outside the volcano it is known as lava.

• 1 in every 10 people are in a danger range of an active volcano.

• Fresh lava is commonly between 700°C and 1,200°C .

FACTS ABOUT VOLCANOES