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Global Warming May Have Killed the Dinosaurs
The Fun Guy sent in a link to the American Society for Microbiology site, your leading news source for everything between nano and macro. The site is featuring a story about new research into the KT barrier extinction: the period in history where the dinosaurs went extinct, along with a number of other families of species. For a number of years scientists have theorized that an impact on the Yucatan peninsula was responsible for the species crash, but microbiological examination of marine organisms of the time indicate life persisted for another 300,000 years after the 'Chicxulub impact'. The researchers at Princeton who made this discovery theorize that global warming caused by a volcanic eruption in India is a more likely culprit for the world-wide devastation. The article generalizes that there is no 'smoking gun' for this event, and further research is required.
The most plausible work I've seen on the subject is based on Durda & Kring's recent work on giant impacts and heat of re-entry. Based on the size of the Chixculub (sp?) impact crater, they concluded that the heat of re-entering rock on ballistic trajectories would have heated almost the entire atmosphere to incandescence. This is global warming of a sort, I suppose.
I've seen talks by archaeobiologists who assert that the dinosaurs were simply broiled by the heat coming from the atmosphere. That theory nicely explains why small, burrowing creatures suddenly took off and why the seas weren't as strongly affected by the land: anything small enough to hide in a burrow, or agile enough to swim deep underwater for a few days survived (at least in numbers large enough to propagate); everything else was cooked. It is also consistent with the fossil record, which shows huge amounts of charcoal cinders near the K-T boundary wherever you look, and a drastic change in the types of pollen present.
Disclaimer: I am not a paleontologist, I'm only an astrophysicist.
"The findings suggest that global cooling led to a sea level drop from about 80 m to 30 m that apparently was more detrimental to foraminifera than was the Chicxulub impact, which occurred during the preceding warming." Maybe I'm missing something but I always thought the meteorite caused a lot of dust which obscured the sun and led to global cooling. That's what also happens with a volcano. So the Slashdot article says one thing but the article it cites says another. Hmm.
A professor of mine once pointed out something very interesting about the Indian volcano theory for the extinction of the dinosaurs. The Indian subcontinent was, 65 million years ago, more or less on the exact opposite side of the Earth from what would eventually become the Yucatan Peninsula. Remember that the Earth is really like a huge ball of liquid, molten rock (the mantle) with a thin crust of solidified material on the outside. What happens when you flick a water balloon really hard with your finger, but don't break it? The force of the blow causes waves to radiate throughout the water from the point of impact in all directions, and dissipates against the inside of the balloon. The point of strongest force for these waves will be on the direct opposite side of the balloon from the point of impact, which bubbles out briefly before returning to place.
On a global scale, a massive meteor impact would actually cause massive and very sudden volcanic eruptions on the opposite side of the Earth as it causes a wave of magma to concentrate on one very small spot.