in compiling extinction records through time, such as Jack Sepkoski and David Raup of the University of Chicago, point out that this particular event stands alone in severity compared to all other such events. More than 50% of marine families died out, and this figure is more than twice that for any other extinction. Estimates of the percent of species (belonging to various families) that went extinct in this event vary from nearly 80% to more than 90%. It is clear that the vast majority of animal and plant life on the Earth was extinguished. [Peter Ward & Donald Brownlee: Rare Earth, Why Complex Life Is Uncommon in the Universe, Copernicus Books, 2000, p179] The end-Triassic mass extinction, 202 million years ago: The end of the Triassic period witnessed a significant mass extinction in which about 50% of genera were eliminated. There is still a very poor record for the fate of land life at this extinction boundary, but it is clear that marine life at this time was extensively and catastrophically affected. This mass extinction, like the K/T event described at the beginning of this chapter, was thought to have been brought about by the impact of a large extraterrestrial body, either comet or asteroid. The Manicouagan Crater in Quebec is 100 kilometers in diameter (compared to the approximately 200-kilometer diameter of the Chicxulub Crater associated with the K/T event). This crater has been dated at 214 million years in age, which is older than the age of the Triassic/ Jurassic boundary. Environmental changes other than impact have been associated with this extinction event as well, most notably oceanographic changes creating anoxia in many shallow-water environments at the end of the Triassic. It is difficult, however, to see how such changes could have affected land life, which also suffered significant extinction at this time. The probable cause remains unknown. [Peter Ward & Donald Brownlee: Rare Earth, Why Complex Life Is Uncommon in the Universe, Copernicus Books, 2000, p180] The Cretaceous/Tertiary boundary event, 65 million years ago: The mass extinction of the dinosaurs, as well as 50% or more of the other species then on Earth, has been recognized for more than a century and a half as one of the most devastating periods of mass death in Earth’s long history.
in compiling extinction records through time, such as Jack Sepkoski and David Raup of the University of Chicago, point out that this particular event stands alone in severity compared to all other such events. More than 50% of marine families died out, and this figure is more than twice that for any other extinction. Estimates of the percent of species (belonging to various families) that went extinct in this event vary from nearly 80% to more than 90%. It is clear that the vast majority of animal and plant life on the Earth was extinguished. [Peter Ward & Donald Brownlee: Rare Earth, Why Complex Life Is Uncommon in the Universe, Copernicus Books, 2000, p179] The end-Triassic mass extinction, 202 million years ago: The end of the Triassic period witnessed a significant mass extinction in which about 50% of genera were eliminated. There is still a very poor record for the fate of land life at this extinction boundary, but it is clear that marine life at this time was extensively and catastrophically affected. This mass extinction, like the K/T event described at the beginning of this chapter, was thought to have been brought about by the impact of a large extraterrestrial body, either comet or asteroid. The Manicouagan Crater in Quebec is 100 kilometers in diameter (compared to the approximately 200-kilometer diameter of the Chicxulub Crater associated with the K/T event). This crater has been dated at 214 million years in age, which is older than the age of the Triassic/ Jurassic boundary. Environmental changes other than impact have been associated with this extinction event as well, most notably oceanographic changes creating anoxia in many shallow-water environments at the end of the Triassic. It is difficult, however, to see how such changes could have affected land life, which also suffered significant extinction at this time. The probable cause remains unknown. [Peter Ward & Donald Brownlee: Rare Earth, Why Complex Life Is Uncommon in the Universe, Copernicus Books, 2000, p180] The Cretaceous/Tertiary boundary event, 65 million years ago: The mass extinction of the dinosaurs, as well as 50% or more of the other species then on Earth, has been recognized for more than a century and a half as one of the most devastating periods of mass death in Earth’s long history.
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