Sunday, August 29, 2010

Dinosaurs, Three Major Asteroid Impacts, and Massive Volcanic Eruptions

"No, Seriously, What Killed the Dinosaurs?"
Earth News, Discovery News (August 28, 2010)

"Seems like an easy one to answer: an asteroid around six miles wide slammed into the Yucatan Peninsula. Continent-wide firestorms, planet-enshrouding dust cloud, massive plant death, toxic ozone, carbon monoxide poisoning ... and that's it: one resounding mass extinction all wrapped up in a pretty, hellish package and explained by a big hole in southeastern Mexico, right?

"Well, the more scientists look, the more complicated the answer becomes. For starters, there were a series of truly enormous volcanic eruptions in what is now western India around the same time. Collectively, the Deccan Traps spewed enough noxious gas that some say it was the cause of the extinction.

"Then there's a weird crater-looking structure right next door to the Deccan Traps. If that turns out to be from an asteroid impact, it would be the largest crater found on Earth. Ever. And just this week, a study in the journal Geology reported there may have been yet another impact, in the Ukraine....."

The Discovery News article does a pretty good job of summing up what we know - what we don't know, but can make educated guesses about - and what we quite simply don't know about what happened about 65,000,000 years back when the dinosaurs stopped living.

The two big hits - the one in what's now the Yucatan Peninsula and the other (probable) impact west of where Mumbai, India is today - apparently happened just a few thousand years apart, but not simultaneously. Which raises some questions:

"...The odds of the two rocks being part of a binary system is small -- if they were, they should have hit simultaneously. But they're still suspiciously close together, suggesting that perhaps some great collision in the solar system sent a scatter-shot of space rocks headed our way.

"Meanwhile, we still have to contend with the Shiva structure, a 500 km-wide gouge in the planet off India that could be the scar left by an asteroid several times bigger than the one that caused the Chicxulub crater...."

Add that smaller impact in what's now the Ukraine, and you've got three impacts around the same time: small; medium; and large. Maybe no one of them would have caused enough trouble to kill off the dinosaurs: but all three, only a few thousand years apart? Add the Deccan Traps eruptions, and you've got something like a Hollywood disaster flick: only spread out over a few millennia.

The Lemming was impressed with the last two paragraphs of the article:

"...It's even been suggested that the Chicxulub impact caused the Deccan Traps to erupt, by way of a huge earthquake that rippled through the planet.

"Such ideas may sound a little ludicrous, but that doesn't mean they're wrong. Life is, generally speaking, very resilient, and dinosaurs were no exception. It would have taken a huge cataclysm -- maybe even several in quick succession -- to end their over 150-million-year reign on Earth."

It's a bit of relief to see that someone's been paying attention. Over the third-of-a-billion or so years that things have been growing on Earth, we've had asteroid impacts, massive volcanic eruptions (real eruptions: not that little Mount St. Helens firecracker), and the occasional ice age. If life were the delicate thing that the more strident 'and we're all gonna die' folks seem to think, we wouldn't be here.

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