265K views · 1.6K reactions | Dinosaurs ruled the world for roughly 140 million years—until they suddenly disappeared. https://on.natgeo.com/2ZQ3OfP | National Geographic | Facebook

Geologists have found that the boundary between the Cretaceous and Paleogene layers called the “K–Pg” boundary (previously known as the "K-T boundary"), in many regions is marked by high levels of the rare metal iridium. While it is true that nearly all dinosaur fossils are absent above this K-Pg boundary, the areas with high iridium levels are not restricted to the thin zone that defines this boundary. In fact, in the same regions where the K-PG boundary was discovered, recent studies have iden