Mass extinctions aren’t fun times. There’s a reason (usually more than one, actually) species disappear in droves. That makes untangling these reasons a challenge. The geological crime scene investigation is tough given that clues can be elusive after millions of years, and the events are complex.
The extinction that wiped out (most of) the dinosaurs, for example, saw both a massive asteroid impact and long-lived volcanic eruptions that covered most of what is now India in lava flows. While the impact would have darkened the sky, bringing permanent winter for a number of years, the volcanoes’ injection of greenhouse gases into the atmosphere would have produced a rapid swing in the warming direction when the sky cleared.
The record of that warming in the geologic record isn’t very good, though. The problem has been to find a suitable climate record in rocks that were deposited fast enough to show relatively short time periods in detail. To obtain that sort of record, a team led by the University of Missouri’s Kenneth MacLeod scratched through rocks in Tunisia for crushed up pieces of fossil fish bits.
Source: FS – All – Science – News
Dinosaur-killing impact + volcanoes kept the Earth hot for 100,000 years