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Re: Bernd: Meteor May Not Have Destroyed Dinosaurs Afterall?




> Hello list....  I still don't buy this nickel (poisoning theory)!

You cannot escape the fact that nickel is highly toxic and may well have
contributed to the extinction process.

>The impact altered the Earth's temperature for many, many years,

Did it? Some scientists claim it did but there is little reliable evidence.
Most meteorologists would tell you that, as the thermal pulse passed over
the oceans, the water boiled releasing huge amounts of vapour into the
atmosphere. That vapour would not stay there for very long but would have
rained out, probably bringing most of the dust with it. The atmosphere may
have stabilised in just a few weeks or months.

The extinction pattern of plant life is confusing. Kirk Johnson, of the
Denver Museum of Natural History, has undertaken a study of fossilized
plants which shows that 85% vanished at the end of the Cretaceous. However,
pollen shows an extinction rate of just 30%. Denver USGS researcher Doug
Nichols has found that palms and screw pines, which are easily killed off by
frost, survived across the K-T boundary as far north as Saskatchewan,
indicating that any post-impact cold/dark period lasted only a few months at
most. In New Mexico the extinctions occur exactly at the K-T boundary
without showing the gradation from north to south expected from progressive
cooling. Western North America shows the highest extinction rates while New
Zealand suffered far fewer losses.

The K-T event was clearly highly complex and our models of global
catastrophes are by no means perfect.

Phil Bagnall
www.ticetboo.demon.co.uk






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