The first concrete evidence that an asteroid impact ended the Cretaceous Period was the discovery of an iridium-rich layer marking the Cretaceous-Tertiary (K-T) boundary by a team led by Luis Alvarez in the early 1980s. Iridium is very rare in Earth’s crust, but is considerably more abundant in asteroids, leading geologists to conclude that the layer originated from an asteroid impact. One area where this layer is exposed is in several places near Raton, New Mexico. After our trip to Great Sand Dunes National park last week, we took a little side trip so I could see the K-T iridium layer, conveniently marked by a sign west of Raton.

Google map showing the location of the iridium layer exposure:

Grace and Peace