Volcanic eruptions come in all sizes and can cause damage on a local, regional or global scale. On a local scale lava flows can cause damage to property (Hawaii, Etna) and mudflows can lead to loss of life/property and can destroy vital communication links (Ruapehu,NZ). On a regional scale some eruptions like Mount St. Helens can devastate large areas and disrupt aviation. On a global scale eruptions that transport material high into the stratosphere can affect our climate (Pinatubo, El Chichon). Eruptions at the other side of the world can affect the UK climate.

It has been suggested that large volume, prolonged volcanic eruptions that punctuate geological time are in some cases associated with mass extinctions. Such huge outpourings of lava are found in India, South Africa, Antarctica, Greenland/Scotland, Yemen-Ethiopia, Washington-Idaho USA etc . Maybe such volcanic activity contributed to the extinction of the dinosaurs or was it a meteorite?

Volcanoes transport molten rock to the surface of the Earth and in so doing provide information about processes deep within the Earth. If during their passage to the surface they pick-up fragments of the Earth then these rocks and minerals provide a unique insight into the nature of the Earth sometimes at depths of 200-400km. The rocks from 200-400km down in the Earth contain garnets, pyroxenes and olivines. Kimberlite volcanoes in South Africa and Canada are renowned for their diamonds some of which are 3,000,000,000 years old (i.e., 3 billion years old).

Volcanic rocks come in a variety of colours some black (basalt), grey (andesite), or pink (rhyolite) and they can contain a variety of crystals - quartz (rhyolites), feldspar (andesites) and olivine (basalts). Volcanic rocks erupted some 3-4 billion years ago are called komatiites and they provide vital evidence about the nature of the early Earth.

Geology Department, Royal Holloway University of London, Egham Hill, Egham, Surrey,
TW20 0EX
Tel: +44 (0)1784 443581 Fax: +44 (0)1784 471780