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Thursday, 22 November, 2001, 19:32 GMT
Dino asteroid led to 'global devastation'
Asteroid impact: BBC
The impact would have shaken the affected planet
Helen Briggs

The asteroid thought to have wiped out the dinosaurs destroyed plant life thousands of kilometres from where it struck, say scientists.

Fossils uncovered in New Zealand point to major disturbances in climate that led to the death of most trees and flowering plants.

Clues from the plant fossil record suggest that even the Southern Hemisphere experienced an artificial winter, acid rain, and raging forest fires.

This is the first clear fossil evidence for destruction of plant life so far from the Mexico coast, where the space object is believed to have landed.

Dr Timothy Flannery, an expert at the South Australian Museum in Adelaide, told BBC News Online: "The asteroid devastated pretty much everything.

"This was a case of global devastation rather than North American catastrophe."

Global disaster

About 65 million years ago, 70% of life, including the dinosaurs, suddenly disappeared from the fossil record.

By piecing together geological and other evidence, scientists are building up a picture of what happened.

The idea is that a giant asteroid about 10 kilometres wide, travelling at 90,000 km/hour slammed into the Earth at the southern margin of North America.

It probably landed close to what is now the Yucatan peninsula, an area that was then a shallow tropical sea.

The damage to North America is unequivocal. According to fossil deposits, the Gulf Coast was emptied of life. On land, forests were flattened, fires raged and four out of five plant species died out.

What happened further afield is harder to establish. There has been very little clear fossil data from places like Australia and Antarctica.

Now, geologists at the Lund University, Sweden, and the Institute of Geological and Nuclear Sciences, a research company owned by the New Zealand Government, have reported new fossil evidence in the journal Science.

It was found on the South Island of New Zealand, which is situated about 11,000 km (almost 7,000 miles) from Mexico.

Ancient layers of rock from the Moody Creek mine on the west coast reveal a characteristic accumulation of fern spores and pollen just after the impact is thought to have occurred.

Climate change

It appears that what was once a swamp forest rich in trees and flowering plants was reduced to little more than a bed of ferns.

Dinosaur footprints, Bolivia
Dinosaurs left their footprints on Earth but plant evidence is harder to find
The mighty eruption of the Krakatoa volcano in 1883 had a similar effect on plants. Bare soil was gradually colonised by only the most hardy of plant species, the fern.

This suggests the impact off Mexico triggered global changes across most of the planet.

Dust would have been blasted into the atmosphere, cutting off sunlight and triggering a spell of dramatic cooling.

Learning curve

There would have been freezing temperatures on the ground and too little light to support photosynthesis. The end result, it seems, is that many land plants were destroyed.

Scientists are searching for similar fossil evidence on other southern continents that could add to the growing picture of how the dinosaurs died out.

According to Dr Flannery, who wrote a commentary on the new research in Science, the asteroid scenario is now a strong hypothesis.

But he says there will always be doubts over anything relating to the history of the Earth.

See also:

08 Mar 01 | Sci/Tech
'Quick' demise for the dinosaurs
08 May 98 | Sci/Tech
Space dust 'did for dinosaurs'
18 Nov 98 | Sci/Tech
Sea clue to death of dinosaurs
27 Nov 01 | Sci/Tech
Chaos clues to dino demise
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