Deccan Traps lavas east of Mumbai show clear evidence of multiple layers deposited by repeated eruptions. (credit: Mark Richards, UC Berkeley)
There have been a number of mass extinctions in the Earth's past, and not all of them have an obvious cause. But the one that ended the dominance of dinosaurs is an embarrassment of riches: it has two viable candidates, either of which could have easily caused extinctions. It's left geologists asking, “Which was worse: The asteroid or the eruptions?”
The asteroid is familiar to most people, but a truly incredible series of eruptions were also going on in what is now India, spewing up over a million cubic kilometers of basaltic lava along with noxious and climate-changing gases. Neither one of these catastrophes represent a relaxing day at the beach for living organisms, but was their combined unpleasantness required for the mass die-off? And was their timing purely coincidental?
In order to answer those questions, we have to know the timing really well. Really, really well. Considering that we’re talking about events 66 million years in the past, it doesn’t take much in the way of error bars on your dating measurements to keep the picture just a little too blurry.
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