[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Crater may reveal how dinosaurs became extinct

__________________ Forward Header __________________________________
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 
Seen in  on 14 August 1996

[ 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
This has been reported via the Fortean Times On-line 
Reporting service at
 >>> http://alpha.mic.dundee.ac.uk/ft/ft.html