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Re: Giant Impact Near India -- Not Mexico -- May Have Doomed Dinosaurs



Rescued from truncation, with my comments inserted:

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> "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 years ago.
> 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.

Will be interesting to learn what the participants will say...

> "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."

I don't quite see why Chatterjee talks about -- no, not a manuscript in press or something; a meeting abstract that hasn't even been presented yet. Sure, he's been talking about it for over 10 years, but at least some people who work on impacts call it science-fiction... he'd better have some pretty hard evidence this time.

> 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.

Hard to imagine how anything on the Seychelles survived this! Yet, the Seychelles have an endemic clade of frogs and another of caecilians.

> 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."
>
> AlphaGalileo =
> http://www.alphagalileo.org/ViewItem.aspx?ItemId=3D61939&CultureCode=3Den=
>
> and
>
> http://gsa.confex.com/gsa/2009AM/finalprogram/abstract_160197.htm
>
> Luis Azevedo Rodrigues
> Paleontologist/Science communicator/Teacher
> Publico newspaper invited blog
> Ciencia Ao Natural
> http://cienciaaonatural.net/
> laz.rodrigues@gmail.com
> Twitter - http://twitter.com/CienAoNatural
> Icnodinos
> http://www.mnhn.ul.pt/dinos/public_html/