The KT extinction is basically the extinction event that wiped out the dinosaurs. As anyone from 5 to 100 knows the dinosaurs reign of supremacy on earth was ended by among other possible causes by the impact of a massive meteor. The Kt extinction is called so since it occurred during the Cretaceous Tertiary period around 66.5 million years ago. We know about if from various pieces of geologic evidence. For example, there is a unique layer of sediment called the Kt layer. Also there is the massive crater on the Yucatan peninsula were the fatal impact occurred.
Scientist Hypothesize that an event happened that caused a massive amount of particle to be ejected into the Earth’s upper atmosphere creating the equivalent of a nuclear winter. This blocked out sunlight and caused many organisms that relied on photosynthesis like plants and plankton to die out in massive numbers. The rest was basically a collapse of the food chain. Herbivorous species on land and see died out and the predators that relied on them followed shortly after. Ironically these massive deaths helped to ensure the survival of many organisms like Mammals who would begin to become dominant in the coming geologic era. Scientists believed that the organisms that survived were the ones that were either omnivores or scavengers. This allowed them to survive long enough to propagate and wait for the Earth to return to normalcy.
While many people have general assumptions about the Kt extinction there are some interesting facts that may challenge them. First scientist are not exactly sure that one meteor caused the extinction event. At best there is evidence that several meteor impacts occurred during the time when the Kt extinction occurred. There is also the theory that a more active period of volcanism than normal was enough to cause the reduction in sunlight that caused the extinction event. We have more recent evidence of this being possible from the Krakatoa eruption and the year without summer that it caused.
The last interesting bit of new is that Mammals did not automatically take over. As a matter of fact it is believed that the Kt event wiped out several orders of Mammals like Marsupials in North America and other northern regions.
Regardless of the cause we know that the Kt extinction event was a major turning point for life on planet Earth.
If you have enjoyed this article there are several others on Universe Today that you will enjoy. There is a great article about Kt asteroid theories. There is also an interesting articles about Mass extinctions.
You can also find interesting resources online. There is a great article about the extinction event on the University of Berkley website. You can also check out the Kt extinction page on the carleton.edu web site.
You can also listen Astronomy Cast. Episode 29 talks about asteroids that may threaten Earth.
Reference:
http://www.ucmp.berkeley.edu/education/events/cowen1b.html
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