Volcanoes killed dinosaurs: scientist

Ancient volcanic activity was so intense it could have caused the climate changes believed to be responsible for the extinction of dinosaurs, a French researcher says in a new study. "Volcanism might be a key player in mass extinctions," said Anne-Lise Chenet of the Institut de Physique du Globe de Paris.

Chenet argues that the earth's climate changed after a surge in volcanic activity sent carbon dioxide, a major greenhouse gas, and sulphur dioxide, a source of acid rain, into the atmosphere.

Pro-volcano researchers have long pointed to the Deccan Trap in India, a vast area of volcanic rock thought to have originally contained up to three million cubic kilometres of ancient lava. That many eruptions could have released enough gas to be climate-altering - if they happened in rapid enough succession.

According to Chenet, that's exactly what happened. "We found that the volcanism duration is certainly shorter than it was estimated before," she said. "A succession of different eruptions could lead to climate disequilibrium. If we have no time between two eruptions, we have no time to re-find climatic system balance." Chenet and her team dated the ancient lava flows by examining how the earth's magnetic field has shifted over time.

Using that method, Chenet determined that a volcanic episode may have lasted about a million years, and that in a period of just 30,000 years, a layer of lava 600 metres thick may have piled up. Other scientists believe that about 70 percent of all species on earth - including dinosaurs - died off about 65 million years ago after an asteriod crashed into the Mexican coast, sending tons of dust into the air and setting off a massive climate change.

Chenet points out that over the last 300 million years, all mass extinctions have coincided with major volcanic activity. The Cretaceous-Tertiary mass extinction, when the dinosaurs were killed off, is the largest extinction ever on earth, and killed off all animals larger than 25 kilograms.