Volcanic activity

A volcano is a rupture in the Earth's surface that allows hot (and usually molten) rock, ash and gases originating in the Earth's crust or mantle to escape. Volcanic activity involving the extrusion or expulsion of magma over time tends to form mountains or mountain-like features. Volcanoes occur at divergent plate boundaries (spreading ridges), convergent plate boundaries (subduction zones) and above mantle "hotspots".

Supervolcanoes are an exajerated form of the ordinary volcano and exist at various places around the world. It produces the largest eruptions known on Earth; which have the power to dramatically force a climate change - often lasting years. The most famous of eruptions have been Yellowstone National Park in America (2.2 and 1.3 million years ago) and Lake Toba in Indonesia (75,000 years ago). Each supervolcano has an eruption area hundreds of kilometres wide.

The Lake Toba eruption sent the Earth into a volcanic winter; eradicating 60% of the human population on Earth. Civilisations, cultures and races were destroyed. The occurance of an eruption from a supervolcano is considerably rarer than ordinary volcanoes but catastrophic when they occur. In more recent years, volcanic activity has greatly increased in America's Yellowstone park; which can be quantitatively measured as it shifts the landscape and moves the resident lake into a forest. According to the occurance of previous eruptions, the timescale predicts that an eruption is definately well on it's way to becoming reality.

A documentary from the BBC has been produced (entitled "Supervolcano" in 2000) in which the consequences of a Yellowstone eruption are highlighted. The whole world would be plunged into darkness for several years and most of America as we know it would be obliterated. The problem being that scientists still know so little about these events.

An artist's impression of the result of an eruption is posted with this article as an attachment.