Double whammy hit dinosaurs

The demise of the dinosaurs was triggered by a spectacular and almost unprecedented double whammy for life on Earth.

New evidence shows that a violent volcanic eruption combined with an asteroid collision for disastrous results.

Previously the giant asteroid was thought to have caused the mass extinction 65 million years ago, with its impact leading to a dramatic change in the global climate that dinosaurs were unable to survive.

A new study suggests a more complex catastrophe, instigated by a huge series of eruptions.

The Deccan Traps in Maharashtra, India, are one of the Earth's largest flows of volcanic lava - more than a kilometre deep and covering about 322,000sq km.

Scientists say the Traps were erupting when the asteroid crashed into Mexico's Yucatan Peninsula. The signature of that collision - iridium deposits found buried in 65 million-year-old sediments worldwide - are also found within the lava cores of the Deccan Traps.

Volcanologists have long thought that the eruption, which has been dated to about 65 million years ago, could have spelled disaster for the dinosaurs by releasing vast amounts of dust, sulphur and greenhouse gases into the air.

But the Deccan Traps were thought to have resulted from a series of eruptions over perhaps a million years, which would have given the climate time to adjust.

Now the study by the Institut de Physique du Globe de Paris has shown that a major part of the total eruption occurred over a much shorter time.

Scientists Anne-Lise Chenet and Vincent Courtillot, after studying magnetic signatures of rock stored in lava cores, calculated that at least 610m of lava were deposited in 30,000 years, which would have released enough sulphur gases to alter the global climate dramatically, as well as poisoning the seas with acid.

- INDEPENDENT