Contending Stygimoloch-spinifer dinosaurs in the ecosystem during the transition from the Cretaceous to the Tertiary: 65.5 million years ago was then the meteor impact, the dinosaurs did not survive. Over half of all plant and insect species also died. Photo: Denver Museum of Nature and Science
Read out Now it's official: The meteorite that hit Mexico's Yucatan Peninsula about 65.5 million years ago has caused the extinction of dinosaurs and many other animals and plants. Other explanations for the mass extinction, such as a then highly active super volcano in India today, can not be reconciled with the existing geological data. This is concluded by an international team of 41 researchers after a careful analysis of the data published over the past twenty years and several computer simulations. Accordingly, the impact of about 15 kilometers large rock was so violent that more than half of all living animal and plant species probably died within a few days. The theory that dinosaurs could have died out as a result of a meteor impact comes from the early 1980s. At that time, researchers discovered that in the KT boundary? a rock stratum that is about 65.5 million years old and separates the Cretaceous from the Tertiary Period? Iridium, which is usually very rare on Earth, is unusually strong. Since asteroids and comets contain more iridium than the earth, such enrichment is considered evidence of an impact in which iridium-rich dust is whirled up and deposited on the earth's surface. The other characteristics of the layer indicated a strike in the area of ​​the Gulf of Mexico, where in 1991 the Chicxulub crater, up to 200 kilometers wide, was actually discovered.

Skeptics doubt, however, that the impact and the mass extinction at the end of the Cretaceous time related. Instead, they suspect the cause in what is now India, the so-called Dekkan-Trapp, where at that time there was an active super-volcano that emit large amounts of dust, sulfur, and volcanic gases for over 1.5 million years. However, Peter Schulte from the University of Erlangen and his colleagues have now been able to refute this: The decrease in the quantity and diversity of fossils followed the rise of iridium in the rock so abruptly that the continuous volcanic activity could not have been the trigger? especially because in the 500, 000 years before only slight changes took place. In addition, the frequently expressed thesis that the impact occurred much earlier than the mass extinction, from a misinterpretation of geological data: The impact had the layers in the affected area so confused that they could hardly provide reliable information, the researchers said.

According to them, the scenario after the impact looked like this: The impact triggered immediately devastating pressure waves and a heat pulse, which propagated for long stretches. The continental shelves collapsed, causing earthquakes with a magnitude greater than eleven on the magnitude scale (Mw) and a series of tsunamis. At the same time, huge amounts of dust, soot, rocks and gases were spewed into the atmosphere in just a few minutes, spreading all over the earth, causing acid rain and darkening. The subsequent cooling and the lack of light in turn decimated the surviving plants and thus all dependent animal species.

Peter Schulte (University of Erlangen) et al .: Science, Volume 327, page 1214 ddp / science.de? Ilka Lehnen-Beyel advertisement

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