Cretaceous-Tertiary extinction event

The Cretaceous-Tertiary (K-T or KT) extinction event, also known as the KT boundary, was a period of massive extinction of species, about 65.5 million years ago. It corresponds to the end of the Cretaceous Period and the beginning of the Tertiary Period. (K is the traditional abbreviation for the Cretaceous period. Cretaceous comes from the Latin for chalk, creta. The K comes from the German word for chalk kreide, or possible Greek kreta. The K is used so as to avoid confusion with the Carboniferous period which uses the letter C.)

Further skepticism

Skeptics remain. Although there is now general agreement that there was at least one huge impact at the end of the Cretaceous that led to the iridium enrichment of the K-T boundary layer, it is difficult to directly connect this to mass extinction, and in fact there is no clear linkage between an impact and any other incident of mass extinction, although research on other events also implicates impacts.

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One interesting note about the K-T Event is that most of the larger animals that survived were to some degree aquatic, implying that aquatic habitats may have remained more hospitable than land habitats.

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The impact and volcanic theories can be labeled "fast extinction" theories. There are also a number of slow extinction theories. Studies of the diversity and population of species have shown that the dinosaurs were in decline for a period of about 10 million years before the asteroid hit. Slower mechanisms are needed to explain such extinctions. Climatic change, a change in Earth's magnetic field, and disease have all been suggested as possible slow extinction theories. As mentioned above, extensive volcanism such as the Deccan Traps could have been a long term event lasting millions of years although short in geologic terms.

Related Topics:
Magnetic field - Deccan Traps

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