Did Huge Volcanic Blasts Snuff Out Dinos?

Brian Handwerk
for National Geographic News
August 23, 2005

A buildup of gases caused by huge volcanic eruptions may have killed off the dinosaurs, according to new research from one the largest lava flows in Earth's history.

Known as the Deccan Traps, the massive lava deposits in west-central India are over a mile (two kilometers) thick and span an area comparable to Oregon and Washington State combined.

The geologic formation appeared 65 million years ago—around the time of the Cretaceous-Tertiary mass extinction that wiped out some 85 percent of Earth's species.

A team of French and Indian geologists recently reported that the Deccan Traps lava might have piled up so quickly that climate-altering sulfuric gases from the eruptions could have made Earth's environment deadly to many species.

New tests reveal that one 2,000 foot-thick (600 meter-thick) lava section could have accumulated in just 30,000 years. That's lightning-fast by geologic standards.

Major Eruptions

"Our working hypothesis is that the majority of the total volume of lava might have been erupted in only a few major events spread over only a small fraction of millennia," said Anne-Lise Chenet of the Paris Geophysical Institute's paleomagnetism laboratory.

"Volcanic eruptions can inject large amounts of sulfur dioxide into the atmosphere. If [little] time passes between different volcanic processes, you change the climate and have a big impact on the environment," she said.

"That's why we began the study, because we wanted to know how many different volcanic processes [were] necessary to produce the volume of lava [at Deccan Traps]."

The geologic formation is a vast deposit of basaltic lava, which sprawls nearly 200,000 square miles (500,000 square kilometers). The Deccan Traps are believed to have formed during volcanic activity that spanned about a million years.

But the new dating results suggest that large portions of lava may have come in spurts much closer together than previously thought.

Chenet described her team's research at a joint meeting of the Geological Society of America and the Geological Association of Canada in Calgary earlier this month.

Continued on Next Page >>


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