VOLCANOES

A volcano is a landform (usually a mountain) where molten rock erupts through the surface of the planet.

In simple terms a volcano is a mountain that opens downward to a pool of molten rock (magma) below the surface of the earth. It is a hole in the Earth from which molten rock and gas erupt.

The name "volcano" has its origin from the name of Vulcan, a god of fire in Roman mythology.

As pressure in the molten rock builds up it needs to escape somewhere. So it forces its way up “fissures” which are narrow cracks in the earths crust. Once the magma erupts through the earth’s surface it’s called lava. Also,Volcanoes are like giant safety valves that release the pressure that builds up inside the Earth.

Volcanoes appear at constructive and destructive margins

A magma chamber is  a large pool of liquid rock found beneath the surface of the earth.

A volcano’s main vent is the point in the Earth’s crust where hot magma has reached the surface. The familiar cone-shaped volcano builds up as ash, rock and lava ejected during eruptions fall back to Earth around the vent.

On large volcanoes, magma will reach the surface through several different vents, and not just the main vent. This can form cones, eject lava, and cause destruction.

Pyroclastic flows are fast moving currents of hot gas and rock with travel down hill from a volcano, reaching speeds of 700 km/hour. The gas can reach temperatures of more than 1,000 degrees C, and is one of the greatest dangers from volcanic eruptions.

Volcanic bombs are chunks of lava blasted into the air which solidify before they reach the ground. Some bombs can be extremely large, measuring 5-6 meters in diameter and landing more than 500 meters from the volcanic vent.

•  Volcanic ash consists of small pieces of pulverized rock and glass created during volcanic eruptions. These fragments are so small, and heated to such a temperature that they can be carried in the air for many kilometers.