From Yahoo News:
The mass extinction that opened the door for the rise of the dinosaurs about 201 million years ago may have been caused by a spike in carbon pumped into the atmosphere — most likely by methane released from the seafloor, a new study indicates.
This spike appears to have accelerated the climate change already under way, ultimately leading to the end-Triassic extinction, the researchers say.
Scientists already suspected that rapid warming and changes to ocean chemistry at the time killed off the dinosaurs' competitors, allowing their era to begin. And they knew that, at the time, eruptions of lava through fissures in the Earth's crust pumped carbon dioxide into the atmosphere.
But this new study indicates that something more than the 600,000 years of eruptions, more massive than anything in human history, pushed about half of species to extinction...
Earth's Methane Burp Cleared Way for Dinos