Lava, impact and the end of the dinosaurs
What the Deccan Traps of India can — and cannot yet — tell us about the end-Cretaceous extinction.
A plateau built of lava
Across western and central India lies one of the largest volcanic provinces on Earth: the Deccan Traps. Its stacked basalt flows reach more than two kilometres in thickness in the Western Ghats, and the surviving outcrop still covers roughly half a million square kilometres.
The name comes from the Swedish word trappa, meaning stairs — a reference to the step-like hills formed as individual lava flows erode.
Two events at one boundary
Around 66 million years ago, at the Cretaceous–Paleogene (K–Pg) boundary, roughly three quarters of plant and animal species disappeared, including all non-avian dinosaurs. Two major events coincide with this moment.
The first is an asteroid impact. In 1980 a team led by Luis and Walter Alvarez reported unusually high iridium at the boundary; in 1991 the buried Chicxulub crater in Mexico was identified as the impact site. A 2010 review by 41 scientists concluded that the impact was the primary trigger.
The impact is a documented event. The size of volcanism’s contribution is still being measured.
The second is Deccan volcanism. High-precision dating studies published in 2019 showed that major Deccan eruptions occurred in pulses within roughly a million years spanning the boundary. The two leading research groups disagree, however, on whether the largest pulses came just before or just after the impact.
Why it matters — if large eruptions preceded the impact, volcanic gases could have stressed ecosystems beforehand. If most lava erupted afterwards, volcanism may have shaped the recovery more than the extinction itself.
Where the evidence stands
S.C.O.B.E.A. labels this topic an Unresolved Question. The impact and the eruptions are both documented. Their relative roles are not settled, and we will update this article as new dating work is published.