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RE: Giant Impact Near India -- Not Mexico -- May Have Doomed Dinosaurs
Who would have thought it? Two giant asteroids hitting the planet at the
same time. What are the odds? And still more life forms were extinguished at
the end of the Permian than at the end of the Cretaceous. Hmmm - the cynic
in me regarding asteroid extinctions is getting a little more cynical every
From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] On Behalf Of
Luis Azevedo Rodrigues
Sent: 15 October 2009 17:09
Subject: Giant Impact Near India -- Not Mexico -- May Have Doomed Dinosaurs
"A mysterious basin off the coast of India could be the largest,
multi-ringed impact crater the world has ever seen. And if a new study is
right, it may have been responsible for killing the dinosaurs off 65 million
Sankar Chatterjee of Texas Tech University and a team of researchers took a
close look at the massive Shiva basin, a submerged depression west of India
that is intensely mined for its oil and gas resources. Some complex craters
are among the most productive hydrocarbon sites on the planet. Chatterjee
will present his research at this month's Annual Meeting of the Geological
Society of America in Portland, Oregon, USA.
"If we are right, this is the largest crater known on our planet,"
Chatterjee said. "A bolide of this size, perhaps 40 kilometers (25 miles) in
diameter creates its own tectonics."
By contrast, the object that struck the Yucatan Peninsula, and is commonly
thought to have killed the dinosaurs was between 8 and 10 kilometers (5 and
6.2 miles) wide.
It's hard to imagine such a cataclysm. But if the team is right, the Shiva
impact vaporized Earth's crust at the point of collision, leaving nothing
but ultra-hot mantle material to well up in its place. It is likely that the
impact enhanced the nearby Deccan Traps volcanic eruptions that covered much
of western India. What's more, the impact broke the Seychelles islands off
of the Indian tectonic plate, and sent them drifting toward Africa.
The geological evidence is dramatic. Shiva's outer rim forms a rough,
faulted ring some 500 kilometers in diameter, encircling the central peak,
known as the Bombay High, which would be 3 miles tall from the ocean floor
(about the height of Mount McKinley). Most of the crater lies submerged on
India's continental shelf, but where it does come ashore it is marked by
tall cliffs, active faults and hot springs. The impact appears to have
sheared or destroyed much of the 30-mile-thick granite layer in the western
coast of India.
The team hopes to go India later this year to examine rocks drill from the
center of the putative crater for clues that would prove the strange basin
was formed by a gigantic impact.
"Rocks from the bottom of the crater will tell us the telltale sign of the
impact event from shattered and melted target rocks. And we want to see if
there are breccias, shocked quartz, and an iridium anomaly," Chatterjee
said. Asteroids are rich in iridium, and such anomalies are thought of as
the fingerprint of an impact."
Luis Azevedo Rodrigues
Publico newspaper invited blog
Ciencia Ao Natural
Twitter - http://twitter.com/CienAoNatural