Dinosaurs' dominance 'helped by mass volcanism'

Immense volcanic activity helped the dinosaurs rise to prominence some 200 million years ago, a study suggests.

Dinosaurs were the dominant vertebrates on land for some 135 million years.

While it is widely accepted that an asteroid or comet wiped them out, there has been less agreement on the factors which led to their ascendancy.

Research in PNAS journal suggests volcanic eruptions changed the climate, causing a mass extinction that wiped out the dinosaurs' main competitors.

The scientific paper, by researchers from the US and Taiwan, looked at several lines of evidence such as the remains of plant wax and wood from sedimentary rocks interbedded with lava flows. From these, they were able to extract vital data about the climate at this time.

The lava flows are dated to the end-Triassic extinction, 201.4 million years ago, which wiped out 50% of tetrapods (four-limbed animals) on land, 50% of terrestrial plants and 20% of marine families.

The scientists examined how two different isotopes (or forms) of carbon fluctuated during these volcanic eruptions. They found that the "heavy" form of carbon was depleted relative to the "light" form.

Super greenhouse

They say this reflects disturbances in the carbon cycle at this time, including a spike in atmospheric carbon dioxide (CO2) and aerosols (fine solid particles).

This would have resulted in "super" greenhouse warming, according to lead author Jessica Whiteside, a geologist at Brown University in Providence, Rhode Island.

"We are showing that these events are synchronous with the extinction and that the events all occur within a few tens of thousands of years of the eruption of these huge lava flows," Dr Whiteside told BBC News. ...

via BBC News - Dinosaurs' dominance 'helped by mass volcanism'.