What Really Killed the Dinosaurs? Feature Summary

Type:
Physics in Your World
Title:
What Really Killed the Dinosaurs?
Description:
Dig into rocks around the globe at the right depth and you may find a thin layer like the one pictured above, a geological hint about our planet's past. This sedimentary layer contains much more iridium than the surrounding layers, and the element iridium is rarely found on Earth but plentiful in rocks in space. For this reason, some scientists believe that there was an enormous meteorite impact that covered the planet in its dust.

The iridium layer supports the impact catastrophe theory that dinosaurs of the late Cretaceous were killed by a meteorite impact and its ensuing planet-wide effects. However, new evidence suggests the crater thought to be responsible due to its iridium content (pictured at right) happened before the mass extinction. See What Really Killed the Dinosaurs? for more on the debate.

(This feature was updated on July 31, 2013.)
Image:
image credit: Eurico Zimbres, Wikimedia Commons (taken at the San Diego Natural History Museum); <a href="http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Tertiary_extinction_event" target="_blank">image source</a>; <a href="http://www.physicstogo.org/images/features/K-T-boundary.JPG" target="_blank">larger image</a>
image credit: Eurico Zimbres, Wikimedia Commons (taken at the San Diego Natural History Museum); image source; larger image
Image URL:
http://www.compadre.org/Informal/images/features/K-T-boundary.JPG
Featured:
October 16, 2010 - November 1, 2010