*sighs* YAGUMET: Sea Rise & Fall

If you are curious about Earth's periodic mass extinction events such as the sudden demise of the dinosaurs 65 million years ago, you might consider crashing asteroids and sky-darkening super volcanoes as culprits.

But a new study, published online June 15, 2008 in the journal Nature, suggests that it is the ocean, and in particular the epic ebbs and flows of sea level and sediment over the course of geologic time, that is the primary cause of the world's periodic mass extinctions during the past 500[sc1] million years.

"The expansions and contractions of those environments have pretty profound effects on life on Earth," says Shanan Peters, a University of Wisconsin-Madison assistant professor of geology and geophysics and the author of the new Nature report.

In short, according to Peters, changes in ocean environments related to sea level exert a driving influence on rates of extinction, which animals and plants survive or vanish, and generally determine the composition of life in the oceans.

Despite what Peters' statements, this is not a new theory. This is actually a rather old one. One that had some nontrivial work done on it by Dr Anthony Hallam et al. He referred to this as the 'regression-transgression' scenario. He talks about it in Catastrophes and Lesser Calamities published in 2004. By this point he'd been advocating the correlation between the sea level changes and mass extinctions for more than 20 years. The problem is that the sea level changes are a correlation and sometimes even a symptom of something else happening.

Frex, the sea level fall in the Ordovician that appears to have driven the mass extinction, yes, but it was a symptom caused by glaciation. Furthermore, how does sea level change effect the planktonic fossils? Specifically those that are photosynthetic that got mopped at the end of the KT/K-Pg? Or the benthic fossils during the PT Extinction? I said it before and I will say it again: the cause of a mass extinction needs to fit the evidence or symptoms of the extinction, not just be chronologically convenient.