MASSIVE volcanic eruptions occurring in rapid succession in India some 65 million years ago could have caused the mass extinction that wiped out the dinosaurs.
The K-T mass extinction is usually attributed to a 10-kilometre-wide asteroid smashing into the Earth, creating the Chicxulub crater off the coast of Mexico. But some researchers have long argued that the volcanic eruptions that formed the Deccan Traps in west-central India contributed to the demise of the dinosaurs. The Deccan Traps were deposited in fits and starts over a period of a million years, forming layered basaltic rock about 2 kilometres thick. However, many scientists think that the eruptions were too infrequent to cause drastic environmental damage.
Now, Anne-Lise Chenet of the Paris Geophysical Institute in France and colleagues from France, India and the UK have shown that volcanic eruptions formed the Deccan Traps more quickly than previously thought: a 600-metre-thick slab of lava built up in less than 30,000 years. They think that this rapid outpouring is likely to have injected volcanic gases high into the Earth鈥檚 atmosphere, catastrophically altering the climate and suffocating much of life on Earth.
Advertisement
鈥淭he rapid outpouring of lava is likely to have injected volcanic gases high into the atmosphere, suffocating much of life on Earth鈥�
The team drilled cores from the upper 600 metres of the Deccan rocks. In each layer of lava, they found magnetic minerals that would have lined up with the Earth鈥檚 magnetic field at the time the lava was deposited. Comparing these to data on how Earth鈥檚 magnetic field has changed over time enabled the researchers to estimate how long each volcanic outburst lasted.
The magnetic dating showed that the section built up over a period of between 12,000 and 27,000 years. 鈥淭here were no major periods of volcanic inactivity during this time, meaning that the environment would have been deeply stressed by the injection of volcanic gases, with no time to recover before the next volcanic eruption,鈥� says Chenet.
But scientists studying the Chicxulub impact are not convinced. 鈥淭he fossil record shows that the extinctions coincide with the impact, rather than the volcanism,鈥� says Philippe Claeys from the Free University of Brussels (VUB) in Belgium. Meanwhile, Jan Smit from the Free University of Amsterdam is dubious about the dating methods. 鈥淔rom what I know about magnetic field stability these 30,000 years may well be 500,000, if not more,鈥� he says.
Chenet presented the results at the Earth System Processes conference in Calgary, Canada, last week.
Dinosaurs 鈥� Learn more in our comprehensive special report.
