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Crater may reveal how dinosaurs became extinct
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Subject: Crater may reveal how dinosaurs became extinct
Author: forteana@lists.primenet.com at smtp-fhu
Date: 14/08/96 03:14
The following was reported by Andy C using
the Fortean Times - On line reporting service
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Seen in on 14 August 1996
BY NIGEL HAWKES SCIENCE EDITOR
[ Nigel Hawkes is the science editor for the Times of London. Does he
really also have an affiliation with the Fortean Times, or is there
some confusion here? -- MR ]
BRITISH scientists will set out to solve a 65-million-year-old mystery
next month.
They will measure a crater in the Yucataan Peninsula in Mexico
that is believed to have been created by the impact of the meteorite or
comet that killed the dinosaurs.
The crater, the largest known on Earth, is buried under up to three
kilometres of more recent sedimentary rock. It could be anything
between 180 and 280 kilometres across, Dr Dave Snyder, of the
Department of Earth Sciences at Cambridge, said.
If the crater lies at the low end of the range, the object that made it
was probably too small to have caused mass extinctions. At the top end,
it was "undoubtedly large enough", Dr Snyder said. If an object of this
size crashed on Oxford, its crater would swallow everything from
Cardiff across to London, and Derby down to Southampton.
The team, which includes Jo Morgan and Mike Warner from Imperial
College, and scientists from the US, Canada and Mexico, will use ways
of measuring earthquakes to size the crater. Dr Snyder will be aboard
the Sigma, an exploration ship fitted with 48 compressed-air
chambers capable of making a loud blast. Onshore in Mexico, the
Imperial College team will record the sounds and measure how they are
reflected from different layers in the Earth's crust.
Dr Snyder said: "The density of the rock and the boundaries between
different types will affect how these waves travel. Because the area of
the crater covers both land and sea, we'll need to use ocean-bottom
seismometers and land-based seismic stations." Gravity surveys have
shown the existence of a ring-shaped feature underground, but the
seismic results should confirm that it is an impact crater.
There are already clues suggesting that the dinosaurs' extinction
coincided with an impact from space. The most persuasive is the
discovery in rocks of the appropriate age of a layer rich in iridium,
an element rare on Earth but commoner in meteorites and comets.
But proving that the Yucataan was the point of impact of an object big
enough to account for the global changes that killed the dinosaurs
would be a big step forward. If it was, the debris of the impact would
have been enough to block out sunlight for tens of years.
Dr Snyder said that limestone sediment in the waters of the Caribbean
would have been vaporised and, mixed with the moisture in the air,
would have caused acid rain, killing off the plankton in the seas.
Death would have spread up the food chain.
The team expects to make its measurements at the end of next month, and
take about a year to analyse them.
Contact email address: acobley@mic.dundee.ac.uk
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This has been reported via the Fortean Times On-line
Reporting service at
>>> http://alpha.mic.dundee.ac.uk/ft/ft.html