Apr 11 2022
The Day the Dinosaurs Died
This is one of the coolest science news stories of the last decade, and I’m a bit surprised it’s not getting more play. Paleontologists have discovered and been examining a fossil deposit from the exact day that the asteroid hit 66 million years ago, at the K-Pg boundary. The site is in Tanis (isn’t that where the Ark of the Covenant was found?) North Dakota (Oh, so no). Actually it’s the Tanis site within the Hell’s Creek formation, which is a productive fossil bed. How can scientists be sure what they are looking at comes from the time of impact? That’s one of the interesting parts of the story.
What appears to have happened is that a large asteroid, about 12 km wide, struck the Yucatan peninsula in the Gulf of Mexico. The crater (Chicxulub crater) from the impact can still be seen. The impact threw a lot of material up into the atmosphere. It also caused a massive tidal wave that spread out, sending material along the Gulf shore, across Mexico, and up along the coasts. But part of this wave also snaked north along a riverbed that led inland to where modern day Tanis is, 3,000 km away. There the water came to rest in a large basin. The wave had swept up sea and land creatures, depositing them in a jumble in the basin. That is one of the lines of evidence that this fossil deposit is a direct result of the impact, the mix of land and sea creatures so far inland, and the fact that the deposit appears to be the result of a sudden chaotic event. It would take something massive to do that, like a meteor impact in the gulf.
An interesting technical detail is that the wave was likely only partly a tidal wave phenomenon from the “splash” of impact. Published evidence indicates that the deposit also likely coincided with a seismic wave – a harmonic wave in the body of water resulting from the impact. So it was more like a megatsunami.