Life › The age of dinosaurs › K–Pg extinction: end of the non-bird dinosaurs
Deccan Traps eruptions
c. 66.3–65.5 million years ago· Event· Earth, climate & extinctions
Strong evidenceGood evidence; dates or details still being refined.
A vast series of lava eruptions in western India that overlapped the asteroid impact and the end of the dinosaurs.
See it on the Life map →What happened
The Deccan Traps are stacked lava flows in western India, in places more than 2 kilometers thick; 'traps' comes from the Swedish word for stairs, after the step-like hills. They formed as India drifted over a mantle hot spot now under Réunion Island. Eruptions began roughly 300,000 years before the asteroid struck and continued for several hundred thousand years after, releasing huge amounts of carbon dioxide and sulfur gases.
Why it matters
One of the largest volcanic outpourings in Earth's history, it is the main rival, or partner, to the asteroid as a cause of the K–Pg extinction.
The evidence (fossils, genes, rocks)
Uranium–lead and argon–argon dating of ash beds and lava flows (major studies 2015–2019), plus mercury spikes and warming signals in ocean sediments from the same interval.
Still debated
Whether most of the gas escaped before or after the impact, and how much it mattered, is still argued; most researchers now see the asteroid as the main killer.
Connections (2)
▸Deccan Traps eruptions may have contributed to K–Pg extinction: end of the non-bird dinosaursDebated
The connection
Deccan eruptions released vast amounts of carbon dioxide and sulfur gases before and after the impact. Some researchers, notably Gerta Keller of Princeton, argue the volcanism stressed ecosystems through warming, acidification and cold snaps, weakening life before the asteroid or even causing most of the extinction. Most now see it as a secondary factor at most.
When and how
Western India, about 66.3–65.5 million years ago, with eruption pulses on both sides of the impact; key dating studies came from Princeton and Berkeley teams, 2015–2019.
How sure are we?
Ocean sediments show warming of roughly 2–4 °C a few hundred thousand years before the impact, along with mercury spikes linked to the eruptions.
Debates and open questions
Studies in 2020 found the extinction pattern fits the impact far better than volcanism, but whether Deccan gases slowed recovery afterward is still debated.
▸Deccan Traps eruptions may have been intensified by Chicxulub asteroid impactDebated
The connection
In 2015 Mark Richards, Paul Renne and colleagues proposed that seismic waves from the impact, equal to a magnitude 9 or larger earthquake, shook loose magma beneath India. On this view the Deccan Traps were already erupting, but the largest outpourings came soon after the impact.
When and how
Western India, within about 50,000 years after the impact 66 million years ago; proposed by a University of California, Berkeley team in 2015.
How sure are we?
Dating suggests eruption rates and lava styles changed near the impact, but dating precision of tens of thousands of years cannot prove cause and effect.
Debates and open questions
Other dating studies (2019) find eruption pulses that do not line up neatly with the impact, so the trigger idea remains unproven.