K-T boundary
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K-T Boundary
Geologists' shorthand for the boundary between the rocks of the Cretaceous and the Tertiary periods 65 million years ago. It coincides with the end of the extinction of the dinosaurs and in many places is marked by a layer of clay or rock enriched in the element iridium. Extinction of the dinosaurs at the K-T boundary and deposition of the iridium layer are thought to be the result of either impact of an asteroid or comet that crashed into the Yucatán Peninsula (forming the Chicxulub crater), perhaps combined with a period of intense volcanism on the continent of India.
© RM 2009. Helicon Publishing is division of RM.
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