66 million years ago, there was a Very Bad Day for nearly everyone on the planet. That’s when the asteroid responsible for ending the age of the dinosaurs crashed into the Yucatan Peninsula and destroyed about 78% of all species.
This picture from Trinidad Lake State Park in Colorado shows one of the places where the impact is still visible: known as the K-Pg boundary, for “Cretaceous -Paleogene”, it is distinguished by a thin line, often containing much more of the element iridium than normally found on earth, or a layer of ejecta from the asteroid impact that was hot enough to melt the sand it pelted into glass. The second image shows the layers in more detail.
The asteroid was only about six miles wide, but crashing so fast — 50,000 feet in its last second — that the earth’s atmosphere heated to 400-600 degrees Fahrenheit. The impact catapulted burning rocks at speeds faster than the escape velocity of the planet, which hailed back down to ignite fires around the globe. The fires and debris in turn covered the atmosphere and temperatures sank 20 degrees Fahrenheit, as photosynthesis halted due to the obliteration of the sun’s light.
The K-Pg boundary shows massive extinction, as the fossilized flowering plants of the Cretaceous layer disappear. In the Paleogene layer above, the plants that re-appear first are ferns: they were able to germinate upon landing without being dependent upon pollenization with receptive flowers.
This Very Bad Day set the stage for the rise of mammals. It was creatures who were able to burrow and survive off of underground plant life during the asteroid-induced and decades-long winter who survived, and some of these were our ancestors.
Source(s): Second image _Geology_, vol 37, 2009, Claire Belcher
