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Maybe It Wasn't The Meteor, After All
An anonymous reader writes "In one new argument, David Penny of Massey University in New Zealand and Matt Phillips from the University of Oxford contend the fossil record and the evolution of animals through modern times suggest the demise of dinosaurs began several million years before the catastrophic asteroid collision.
'"We agree completely with the geophysicists that an extraterrestrial impact marks the end of the Cretaceous," said Penny, in a statement reported in newspapers and on the Internet this week. "But after 25 years [scientists] have still not provided a single piece of evidence that this was the primary reason for the decline of the dinosaurs and pterosaurs."'"
Space.com has an article on this, and has an interesting view. The article can be found here.
Logic, macros, and more
Really, the "slow decline" idea is, by itself, an old and fairly tired argument. There is little dispute that the dinosaurs were in decline in N. America before the K-T boundary, but the fact of decline doesn't imply that the deathblow wasn't strongly related to the Yucatan impact.
Most people who have studied the Earth's history of mass extinctions have come to understand a few important points. First, it doesn't appear that bolide impacts are the primary cause of many of them. Second, when mass extinctions occur, they appear to have been the result of several factors acting simultaneously to cause a collapse of the food chain.
At the K-T boundary there were several things going on at once, and they appear to have (together) resulted in the extinction of the dinosaurs:
First, the dinosaurs were already in decline in N. America, with most dinosaur populations concentrated in N. America and part of Asia. Major disruptions in the breeding cycle of dinosaurs would have been disasterous.
Second, reconfiguration of the continents was changing the ocean's circulation patterns. This affected climate, ocean temperature, ocean mixing, and most fundamentally ocean productivity.
Third, the dinosaurs weren't the only creatures that went extinct at the KT boundary, lots of things had been in decline, probably due to ongoing climate change & major volcanism...
Fourth, major volcanism was occurring during the end-days of the Cretaceous. High rates of seafloor spreading along a couple major ridges probably changed seawater chemistry, and the Deccan Traps were erupting in the vicinity of Asia. If you're not familiar with the Deccan Traps, imagine 200,000 square miles of volcanic rock a few thousand feet thick -- about 12,000 cubic miles of lava (for reference, that's about half a million times more material than Mt. St. Helens erupted in 1980). This would have been a significant stressor affected climate and biosphere; Asian dinosaurs might have been particularly hard hit, but the presence of this large igneous province bws probably not sufficient to collapse the food web and by itself result in the demise of the dinosaurs.
But fifth, on the other side of the globe from the Deccan Traps, a bolide collided with what would become the Yucatan Peninsula. The sedimentary rocks there contained thick anhydrite deposits (that's calcium sulfate) and thick layers of limestone (calcium carbonate). The blast would have rapidly liberated the sulfate and carbon dioxide from those minerals, then thrown billions of tons of particulate matter in to the stratosphere. The particles thrown up from the impact would have blotted out the sun, while the sulfur rained back as sulfuric acid rain (this isn't good for vegatation or aquatic critters). Darkness would have slowed primary photosynthesis, but even after the skies cleared the climate would have been thrown in to chaos: the CO2 liberated from the blast could have caused severe greenhouse warming in the few thousand years after the impact, wreaking yet more biological havoc. I could keep describing various aspects of the chaos that would follow such an impact, but don't think it's really necessary. The impact may not have, by itself, been enough to kill off the dinosaurs, but it must have severely stressed and already severely stressed ecosystem, and following a multi-faceted attack on the base of the food chain, the top macrofauna would have had a rough go of it.
Finally, the impact event is very strongly correlated with the extinction of the dinosaurs; there's very little evidence that any dinosaurs in N. America survived the impact -- to my knowledge, no dinosaur fossils have been found stratigraphically above the iridium layer (there are cases where fossils could have weathered out of Cretaceous strata and been redeposited on younger Tertiary strata, but that's not evidence for the dinos having survived the boundary).
In conclusion, there's no proof that the dinosaurs would have survived had there not been an impact, nor
If conditions, even millions of years prior to the extinction, were so hostile to reptilian life that the dinosaurs were dying out, conditions for millions of years after must've been considerably worse. How, then, have so many reptiles from that time period survived?
Certainly I believe there was a mass extinction, and that it was caused by a sudden event. Sheer dumb luck is all that is required to explain the survival of reptilian life from this time. Luck, though, tends not to hold out over timeframes spanning tens or hundreds of millions of years.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
I don't know how you can say, "a literal reading of the bible cannot be reconciled with science" when you haven't bothered to even do a Google search regarding your "favorite question."
I think that it would be impossible for anyone to "reconcile" the Bible with science without having an attitude of sincere, intense study of the relevant subjects.
I'll give you a few places you can check out if you'd like.
I think that the survival thing largely comes down to "dinosaurs big, other critters small" rather than being anything very complicated.
The smallest sized dinosaur was chicken-sized, that we know of. A quick google search indicates that a larger crocodile survived the big extinction.