Word: chicxulub
(lookup in dictionary)
(lookup stats)
Dates: all
Sort By: most recent first
(reverse)
...dinosaurs and made way for the rise of mammals. The suddenness with which so many species vanished after that time always suggested a single cataclysmic event, and the 1978 discovery of a 112-mile, 65-million-year-old crater off the Yucatán Peninsula near the town of Chicxulub seemed to seal the deal...
...controversial paper was written by geoscientists Gerta Keller of Princeton University and Thierry Addate of the University of Lausanne, in Switzerland. Both researchers knew that challenging the impact doctrine would not be easy. The asteroid charged with killing the dinosaurs, after all, left more than the Chicxulub crater as its calling card. At the same 65-million-year depth, the geologic record reveals that a thin layer of iridium was deposited pretty much everywhere in the world. Iridium is an element that's rare on Earth but common in asteroids, and a fine global dusting of the stuff is precisely...
...mass extinction level can be seen above this interval," Keller says. "Not a single species went extinct as a result of the Chicxulub impact...
...Chicxulub asteroid didn't kill the dinosaurs, what did? Paleontologists have advanced all manner of other theories over the years, including the appearance of land bridges that allowed different species to migrate to different continents, bringing with them diseases to which native species hadn't developed immunity. Keller and Addate do not see any reason to stray so far from the prevailing model. Some kind of atmospheric haze might indeed have blocked the sun, making the planet too cold for the dinosaurs - it just didn't have to have come from an asteroid. Rather, they say, the source might have...
...rare on Earth but common in asteroids. The iridium layer, mapped by the Alvarezes in scattered sites around the world, suggested an asteroid that vaporized on impact, spreading a cloud throughout the stratosphere. The argument seemed sealed in the 1990s, when geologists realized that a huge crater centered near Chicxulub, Mexico, was almost certainly caused by a giant impact at just the time the extinctions occurred...