For a long time it was suspected that volcanoes were partly responsible for the extinction of the dinosaurs. A team of researchers has now investigated this in more detail. The study could confirm again that something else was the trigger.
|What Really Killed the Dinosaurs.|
|Dinosaurs Extinction volcanoes to blame|
The extinction of dinosaurs and other animals 66 million years ago was caused by an asteroid impact. This has been confirmed by a team of researchers in a new study.
For a long time, massive volcanic activity in the Deccan region in southern India was also discussed as a possible cause. However, according to the study published in the journal "Science", the volcanic scenario does not fit the time frame.
At least half of the degassing of the Deccan volcanism took place well before mass extinction, said André Bornemann of the Federal Institute for Geosciences and Natural Resources (BGR) in Hanover, one of the authors of the study.
|Dinosaurs Extinction volcanoes|
Dinosaur extinction 66 million years ago.
The geologist is part of the international team that examined deep-sea drill cores from the North and South Atlantic and the Pacific, looking at the exact period of time at the boundary between the Cretaceous and the Palaeogene 66 million years ago.
At that time about 75 percent of the animal species became extinct. The scientists used reconstructed temperature changes, fossil finds and models of the carbon cycle for their study.
|the volcanic scenario|
Asteroid impact could have triggered natural disasters.The consequence of the asteroid impact off the Mexican Yucatan peninsula is still visible today in the form of a crater with a diameter of almost 200 kilometres.
The event could have caused tsunamis and bushfires and released huge amounts of sulphur. This hypothesis was recently substantiated by American researchers who analysed the drill core from the impact crater.
Although volcanism in the Deccan region was responsible for a brief warming phase 200,000 years before the extinction event, this did not have any long-term effects on the living environment and climate, said Bornemann.
However, the volcanism itself could possibly have had an impact on the formation of living organisms after the great extinction, the study authors write.
Bornemann participated in the deep-sea expedition of the International Ocean Discovery Program (IODP), during which one of the drill cores for the study was taken near Newfoundland. The coordination office for IODP Germany is located at BGR.
Did volcanoes have anything to do with dino extinction?
Interestingly enough, 66 million years ago, a lava volcano erupted in India, known as the Deccan Trap.
During this process, much of the subcontinent was buried under more than 11,000 feet of basalt (lava rock) and toxic gases were expelled into the atmosphere.
Princeton geoscientists Blair Schoene and Gerta Keller led an international team of researchers that developed the first high-resolution chronology of the Deccan Trap explosions in India. Their research was published in the February 22 issue of Science magazine.
"Everyone has heard that dinosaurs died because of the asteroid that hit the Earth," says Schoene, an associate professor of earth sciences.
"Many people don't know that there have been many other mass extinctions in the last 500 million years and that many of them coincide with large volcanic eruptions" of huge volcanoes called alluvial basalts or large needle provinces.
Dating the rock (Geochronology)
Shaohen uses several techniques of Geochronology, science about age distribution of rocks. The most famous method of geochronology, usually called carbon dating, uses the rate of radioactive decay of carbon-14 to search for fossil ages.
It works on plants or animals several thousand years old, which makes it useful for archaeology but not for 66 million years of basalt. For rocks of mass extinction, geologists have a choice of natural radioactive materials.
Uranium geology makes it possible to determine age very accurately, but minerals containing uranium are rarely found in basalt, a rock composed of massive lava streams; uranium containing zirconium is more common in explosive eruptions of volcanoes like St. Helena, which have richer silica chemistry.