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The end-Cretaceous event is the only mass extinction definitively known to be associated with an impact, and other large extraterrestrial impacts, such as the Manicouagan Reservoir impact, do not coincide with any noticeable extinction events. [249]
In this mass extinction, many commonly recognized groups such as non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-known groups, died out. The cause of the extinction is most commonly linked to an asteroid about 10 to 15 kilometres (6.2 to 9.3 mi) wide [4] [5] colliding with Earth, ending the Cretaceous.
The End Cretaceous extinction, or the K–Pg extinction (formerly K–T extinction) occurred at the Cretaceous (Maastrichtian) – Paleogene transition. [19] The event was formerly called the Cretaceous-Tertiary or K–T extinction or K–T boundary; it is now officially named the Cretaceous–Paleogene (or K–Pg) extinction event.
When dinosaurs got big. Another period of extreme volcanic activity 201 million years ago marked the end-Triassic mass extinction. It has been linked to the breakup of the Pangea supercontinent ...
By the time the Cretaceous-Paleogene, or K/Pg, extinction event was over, about three-quarters of species alive at the time of impact had disappeared forever.
The proposed Shiva crater and other possible impact craters along with the Chicxulub crater have led to the hypothesis that multiple impacts caused the massive extinction event at the end of the Cretaceous period. Chatterjee is confident that Shiva was one of many impacts, stating that "the K-T extinction was definitely a multiple-impact scenario."
A conference dedicated to the end-Cretaceous extinction event was held at Utah's Snowbird Ski resort. [45] Alexopoulos and others compared quartz grains from rocks that had been subjected to various types of geologic forces like bolide impact, volcanism, or tectonic deformation with quartz from the K–T boundary layer.
Luis Walter Alvarez, left, and his son Walter, right, at the K–T Boundary in Gubbio, Italy, 1981. The Alvarez hypothesis posits that the mass extinction of the non-avian dinosaurs and many other living things during the Cretaceous–Paleogene extinction event was caused by the impact of a large asteroid on the Earth.