|
 That is the conclusion of scientists who said on Thursday they
have determined with new precision the proximity of the dates of
these catastrophes: a space rock about 6 miles (10 km) wide striking
Mexico's Yucatan region and colossal eruptions in India.
The two events roiled Earth by throwing dust, ash and harmful fumes
like carbon dioxide and sulfur dioxide into the air, altering the
climate and killing off about 75 percent of all species in one of
Earth's worst mass extinctions.
The researchers said the asteroid strike occurred 66.04 million
years ago, plus or minus about 30,000 years.
They said eruptions in a region called the Deccan Traps were already
underway at a lower intensity but dramatically accelerated after the
asteroid strike as if the powerful impact triggered it. The dating
method they used found this acceleration began within 50,000 years
of the impact, but it could have been in the mere days, months or
years afterward.
 "Within measurement error, they're simultaneous," said volcanologist
Loÿc Vanderkluysen of Philadelphia's Drexel University.
"The two processes in tandem caused the extinctions," added Paul
Renne, director of the Berkeley Geochronology Center and a
University of California, Berkeley geologist, who led the study in
the journal Science.
Scientists have debated for about 35 years which of the two
disasters drove the extinction, some touting one while calling the
other inconsequential.
[to top of second column] |
"The debate has been contentious," Renne said. "Now it's time to
stop dismissing one cause or the other. They clearly happened at the
same time and both contributed."
"An asteroid 10 kilometers across, about the size of Manhattan,
hitting the Earth is traumatic enough. But what followed were the
largest volcanic eruptions the Earth had seen in 60 million years.
And in their wake would have come 4,000 centuries of changing
climate, ocean acidification and acid rains," Vanderkluysen added.
The Deccan eruptions lasted 420,000 years after the asteroid and
extruded enough lava to cover the continental United States 600 feet
(180 meters) deep.
"We as humans wouldn't be here if the dinosaurs had not been wiped
out," said Cal-Berkeley geophysicist Mark Richards, noting the
extinction at the Cretaceous Period's end paved the way for mammals
to become the dominant land animals.
(Reporting by Will Dunham; Editing by Sandra Maler)
[© 2015 Thomson Reuters. All rights
reserved.]
Copyright 2015 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
 |
