What Killed the Dinos? Part 3: Cause or Coincidence


Ok, so meteorite crater found. But scientists still wondered if that was the cause for the dinos’ extinction, writes Lisa Randall in Dark Matter and the Dinosaurs. What such an impact does is hard to imagine, so it needs to be spelled out… step by step.

How much “bang” could a meteorite have carried? At 3 times the width of Manhattan travelling at minimally 20 km per second, it packed more than a billion times the punch of the nukes dropped on Hiroshima:
-          At the impact site, it would have set off extreme winds and waves;
-          The impact would have set off earthquakes across the world. Those would have then set off monster tsunamis across the world;
-          Trillions of tons of vaporized rocks at the impact site would get ejected and spread worldwide. As the red-hot debris fell back to earth, it would start fires triggering the next round of destruction. The earth would be getting cooked;
-          Nitrous and sulfur emissions into the air would trigger off rounds of global warming here, global cooling there. And when the gases finally came down to earth, they would fall as acid rain burning and poisoning everything around;
-          Estimates say more than half the biomass of the earth was wiped out in the first few months. And that wipeout of plants would radiate up the food chain, wiping out even more species further up the chain.

Ok, so the meteorite impact could have caused the dinos to go extinct. But did it? The age of the soil layer’s rocks near the crater was a near perfect match to the window when the dinosaurs went extinct: In 2013, a Berkeley team of scientists found that the Chicxulub impact and the mass extinction were “less than 32,000 years apart, an incredibly accurate measurement for events that took place so long back”. That’s within 0.05% of the time of the meteor impact/dino extinction.

Keep in mind that the basis for the two dates are independent of each other (material found in the crater site v/s fossil records worldwide). The odds of the two events being independent were now considered very small indeed. After all:
-          A chain of events that would follow a massive meteorite impact had been identified, which would have been devastating for life;
-          The time of the impact and the mass extinction coincided;
-          And the impact site had been found.

It was only in this decade that “41 experts on paleontology, geochemistry, climate models, geophysics, and sedimentology” finally decided that too many clues and independent forms of analysis pointed to the same thing, namely that the meteorite triggered a mass extinction across the globe.

Including, as Randall puts it, “its most notable victim – the venerable dinosaur”.

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