Iran Daily

Dinosaurs wiped out by asteroid, not volcanoes, researcher­s say

-

A 66-million-year-old murder mystery has finally been solved, researcher­s say, revealing an enormous asteroid struck the killer blow for the dinosaurs.

The Cretaceous/paleogene extinction event resulted in about 75 percent of plants and animals — including nonavian dinosaurs — being wiped out. But the driving cause of the catastroph­e has been a topic of hot debate, the Guardian reported.

Some scientists say the 10km-wide asteroid that smashed into Earth and created the Chicxulub crater was the chief cause, with the strike sending up vast quantities of material that blocked the Sun, triggering a prolonged, cold period that caused devastatio­n.

However, others say volcanic activity in India’s Deccan Region was the main driver, causing large-scale climate change. Volcanic eruptions have previously been found to have driven other mass extinction­s, including the endpermian mass extinction.

Still others have suggested the two acted together, possibly with the asteroid the last straw after a long period of instabilit­y caused by volcanic activity.

Now researcher­s say they have unpicked the mystery by modelling the ecological effects of the different possibilit­ies.

“When we produced the different scenarios both for either the two things happening together, or completely separated, we see the asteroid is [the] only [event] that can completely eradicate the habitats that can be suitable for dinosaurs,” said Alfio Alessandro Chiarenza, first author of the research at University College London.

Writing in the Proceeding­s of the National Academy of Sciences, Chiarenza and colleagues report how they built models to explore how the different disasters would have affected the planet’s climate and, crucially, the habitats in which dinosaurs lived, from tyrannosau­rs to the armored ankylosaur­s.

The team first looked at a five percent reduction in sunlight — the top end of what would be expected from the sulfur dioxide and debris from the volcanic eruptions blocking out light, but a very mild scenario for the asteroid impact. The model suggested this would not have led to extinction of the dinosaurs, although their habitat would have been reduced because of the long-term impact on factors such as temperatur­e and rainfall.

However a 10-20 percent reduction in sunlight, the lower to extreme range expected from the asteroid strike, would have devastated dinosaur habitats, with a dimming of 15 percent or more destroying them completely.

“Even if the volcanic eruptions had not happened, the extinction would have occurred in any case as the [impact] event was severe enough to eradicate dinosaurs’ habitats worldwide,” Chiarenza told the Guardian.

In fact the team suggests that rather than wiping out life, the pulses of global warming resulting from carbon dioxide released from the volcanoes could have buffered the cooling from the asteroid strike and helped life recover — although the fate of the non-avian dinosaurs would have remained the same.

“We [thought]: Ok… is that something completely outrageous to suggest?” said Chiarenza.

“But actually it seems that recently there have been studies that have been looking at this very thing in the geologic record, showing that some pulses of warming, particular­ly after the impact event, seem to have boosted somehow the recovery of life, particular­ly plant life, but also [led to] the increase of body size in mammals and in diversity.”

Read the full article on: www.irandailyo­nline.ir/news/270835.html

 ??  ?? ALAMY
ALAMY

Newspapers in English

Newspapers from Iran