British experts have warned the UK government about the dangers of supervolcanoes. An eruption of one of these volcanic monsters could upset the global climate for years, leading to failed harvests and widespread famine. Laurence Spicer has more.

The warning, from Britain's Geological Society, was given to a science committee of the Westminster Parliament on Thursday. Of particular concern to scientists is a volcanic giant lurking beneath the Yellowstone National Park in the USA. The last time an eruption occurred there, around 640 thousand years ago, it formed an 85 kilometre-wide crater. Supervolcanoes are different from their more common cousins. A supervolcano forms as a large bubble of molten magma close to the surface of the planet, rather than as a distinctive cone-shaped mountain. Very occasionally the molten rock erupts, with devastating effect. Professor Bill McGuire of University College, London.

Professor Bill McGuire said:

The impact will be huge for everyone on the planet. If we look at the last super-eruption it ejected something like 3 thousand cubic kilometers of debris into the atmosphere. Now this spreads out over the planet, it cuts down solar radiation, it creates a volcanic winter. So you have no global harvest for two or three years, maybe. People will just starve to death.

At the moment nothing can be done to stop such an eruption, and scientists say one is inevitable sooner or later. But increased monitoring of sites of concern could give mankind sufficient warning to prepare for the worst. In London, this is Laurence Spicer.

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