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Page last updated at 13:21 GMT, Tuesday, 11 May 2010 14:21 UK
How erupting volcanoes marked Devon's landscape
Ed Goodridge
By Ed Goodridge
BBC South West


Dr Richard Scrivener talks about Devon's volcanic past

When you look at Devon's rolling green hills, it's hard to imagine that this landscape was born out of a tropical environment with volcanoes erupting under water and on the edge of deserts.

But that's just what it was like between 250 and 400 million years ago.

And today the remnants of that fiery past can still be seen in some unexpected places.

Take Rougemont Castle in Exeter built on an extinct volcanic vent and Brentor, with its church towering on a mass of basalt lava.

Dr Richard Scrivener spent much of his life studying the geology of Devon - working with the British Geological Survey.

He says most volcanic rocks in the county come from the Permian age (around 285 million years ago).

Devon was then at the centre of a vast continent close to the equator.

An old volcanic quarry has been turned into a rock garden at Killerton
An old volcanic quarry has been turned into a rock garden at Killerton

It was on a boundary between two chunks of the earth's crust which were colliding and melting.

The region was an arid desert rather like Ethiopia today with volcanoes lying along the edge of a rift valley.

They erupted over the desert sands and it is these lava flows that are found today in quarries like the one Richard showed BBC Devon around near Crediton.

The stone found here was used to build the town's church.

"If you go out into West Devon towards Cornwall you have some of the submarine volcanoes - a good example is Brentor which is on a pile of volcanics that came out on to the seafloor," said Dr Scrivener.

All this volcanic activity happened a long time ago, the cones and craters have been eroded away and there's no chance of another eruption so don't panic !

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