(image from pnas.org)
If there is one thing that science does well its agree on things. Ok, so maybe not, but it is known to happen occasionally. Or at least there is strong evidence in support of these events.
Recently a panel of 41 scientists reviewed 20 years of evidence regarding the cause of the Cretaceous-Tertiary (KT) extinction that occurred approximately 65 million years ago - the extinction event that wiped out the dinosaurs long with many other animal and plant species. One explanation put forth for the cause of this extinction is the eruption of massive volcanoes - or multiple impacts combined with volcanic eruptions. Alternatively, and perhaps more widely known, is the suggestion that a single, large asteroid hit the Earth somewhere around Mexico's Yucatan peninsula.
The conclusion? The big rock from space did it. The panel concluded that while large scale volcanism did occur it was too early in Earth's history to account for the extinctions, and that the evidence is strong in the support of the single impact theory.
Check out the article here: http://www.usatoday.com/tech/science/discoveries/2010-03-04-dinos05_N.htm