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By Roland Pease
BBC science correspondent
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Footprints in ash deposits record people
fleeing from the eruption |
Researchers
are warning that the next eruption of Vesuvius could be much more
deadly than the Italian authorities are planning for.
A US-Italian collaboration says deadly blasts have previously
caused devastation which swept well beyond modern Naples.
Italian plans call for the evacuation of 600,000 people from the
city.
But the researchers say up to three million people could be at
risk according to the new assessment.
Vesuvius is best known for its eruption in AD 79, the eruption
that buried the Roman town of Pompeii.
Plans for the evacuation of Naples are based on a similar-sized
eruption in 1631.
But go back about 3,780 years and Vesuvius exploded with even
greater force.
Past eruptions
The new work, published by the US National Academy of Sciences,
shows that in the Bronze Age, the most recent of those eruptions,
hot, ash-ridden flows raced up to 25km (16 miles) to the north-west
of the volcano, over and beyond modern Naples.
Anything within the first 12km (eight miles) would have been
swept away by this pyroclastic surge.
The research has implications for the Naples
evacuation
plan |
To the east
of the volcano, tens of centimetres of pumice rained down on the
surrounding countryside - the weight would crush the roofs of modern
houses.
If the volcanic cycles of Vesuvius are anything to go by, a
repetition of this eruption is as likely as a recurrence of the 1631
event - and Naples needs to realise how bad that could be, the
authors say.
One of the authors, Michael Sheridan, told the BBC: "If we
compare the eruption of the Bronze Age with the eruption that
destroyed Pompeii, we can see that the deposits within Naples
produced by the Bronze Age eruption range in thickness from three
metres down to half a metre; whereas there are no really measurable
deposits from the Pompeii eruption within the city of Naples."
Displaced people
Professor Sheridan said he had been motivated by the US
experience of Hurricane Katrina last year, when authorities failed
to prepare adequately for a well-understood weather disaster.
"The current planning doesn't consider the maximum probable
event," explained Professor Sheridan.
A archaeological dig 15km north-east of
Vesuvius has uncovered victims |
"There
have been notable cases recently where disaster planners have not
taken into account the worst-case scenario and this eruption would
certainly be one of those.
"It actually has a fairly high probability [of occurring] if we
consider there have been eight large eruptions of this kind in the
history of Vesuvius with a separation in time of 2-3,000 years, and
it's been nearly 2,000 years since the last one."
Professor Sheridan recognised the difficulty of evacuating three
million people from a major urban centre.
He noted that, as was the case after Hurricane Katrina,
distribution of water, food, and housing for the survivors and the
nature of the escape routes must also be carefully considered with
an evacuation of such magnitude.
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