Deccan Traps erupt
Huge lava flows build the Deccan plateau of India in pulses before and after the end of the Cretaceous. How much they added to the asteroid's toll on life is debated.
The story
The Deccan Traps are a vast pile of basalt lava in west-central India, erupted around 66 million years ago. Today the lava covers about 500,000 square kilometers and in places is over a kilometer thick, but it once spread over a much larger area, perhaps 1.5 million square kilometers, and totals more than a million cubic kilometers. The word 'traps' comes from a Swedish word for stairs, describing the stepped hillsides the layered flows leave behind. Some single flows traveled over 1,000 kilometers, reaching the Bay of Bengal.
The eruptions followed the breakup of Gondwana, as India drifted north over a hot spot, now under Réunion Island, that melted the rock below. Most of the lava poured out in a few pulses over about a million years, close in time to the end of the Cretaceous. Each eruption released carbon dioxide and sulfur gases that could warm the planet and chill it in turn. What role this played in the extinction of the non-bird dinosaurs, alongside the Chicxulub asteroid impact in Mexico, is debated. Most scientists see the impact as the main killer, with the volcanism as a secondary stress.
Why it mattered
- The debate over the Deccan and the Chicxulub impact reshaped how scientists study mass extinctions.
- The black, fertile soils weathered from the basalt support India's cotton and other crops.
- The eruptions are a record of India's journey across the Indian Ocean toward its collision with Asia.
Contested history
Consensus: The Deccan Traps erupted in pulses around the time of the Chicxulub impact 66 million years ago.
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