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16 October 2014
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Volcanoes - Cause
The Eruption - Pyroclastic Surge
A pyroclastic surge travels on top of the base flow. The surge is made up of hot gases and volcanic ash. The surge usually follows the route of the base flow but can separate from it. On 25 June 1997 the surge separated several times as the base flows twisted and turned through the valleys. Deposits from a pyroclastic surge are a fine covering of ash, a bit like snow. This ash is hot enough to destroy vegetation and burn anything it sweeps through.
Pyroclastic flow enters the sea
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