Hello and

welcome to the naked scientist with me Chris Smith and also with Ginny Smith and you find us this week at the Cambridge Science Center

where we're recording this program which is all about volcanoes in front of this wonderful audience. This month marks 200 years since one of the most dramatic natural disasters in human history,

the eruption of Mount Tambora.

To mark this occasion, we have gathered together a panel of volcano experts to talk us

through what actually happens when a volcano erupts. Now another famous

eruption is that of Mount Vesuvius in Italy. When it erupted in 79 AD it devastated the nearby

towns of Pompeii and Herculaneum. Luckily for us this eruption was extremely

well documented and today we're going to hear some of the excerpts from an eyewitness

account that was written by Pliny the Younger.

His uncle, Pliny the Elder, was an official in the Roman court in charge of the fleet in the area of the Bay of Naples

and he was also a naturalist.

When Vesuvius erupted in 79 AD, his nephew, Pliny the Younger, was staying with him in Mycenum, about 20 kilometers from Pompeii.

Pliny the Younger had a good view of the volcano across the bay to the west and recorded his experiences in a series of letters. In this first excerpt, Pliny writes about first

realizing a mountain later identified as Mount Vesuvius was becoming active.

A cloud from which mountain was uncertain at this distance was ascending, the appearance of which I cannot give you a more exact description than by liking it to that of a pine tree, for it shot up to a great height in the

form of a very tall trunk, which spread itself out at the top into a sort of branches. It appeared sometimes bright and sometimes dark and

spotted, according as it was either more or less impregnated with Earth and cinders. This phenomenon seemed to a man as such learning and research as my uncle, extraordinary and worth further looking into.

While for the Romans it may have seemed that this eruption occurred with no warning signs, we now

know that events in the days leading up to it were caused by the pressure inside the volcano. Pliny wrote,

For several days passed, there had been earth tremors,

which were not particularly alarming

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