If you were to ask the average person what killed off the dinosaurs, most people would say that is was a huge asteroid impact. This impact has been named the Chicxulub impact and it hit the Earth about 66 million years ago (66.236 +/- 0.060 million years ago if you want to get specific).
The crater that resulted from the Chicxulub impact is located along the tip of the Yucatán Peninsula in Mexico. The crater itself is absolutely huge, spanning 180 km in diameter and 20 km in depth. It is one of the largest craters ever found on the face of the Earth, with the asteroid itself being 10 km in diameter. This event was so significant in geologic history that not only did it signify the end of a geologic period (Cretaceous), but also the end of a geologic era (Mesozoic).
One of the largest mass extinction events coincided exactly with the Chicxulub impact at the Cretaceous-Paleogene boundary (formerly referred to as the K-T boundary). Nearly 75% of all life on Earth died off, including the much beloved dinosaurs.
In a paper published in Nature last week, a group of scientists suggest that the mass extinction that occurred at the Cretaceous-Paleogene boundary may not have been caused entirely by the Chicxulub impact. Instead, it is suggested that the mass extinction may have been more of a 1-2 punch.
The Deccan Traps are a massive deposit of volcanic rock in west-central India. It is one of the largest volcanic features on Earth. It is estimated that the volume of rock within the Deccan Traps is 1 billion cu. km. To put things into perspective, this is the volume equivalent to approximately 100 trillion elephants.
The researchers used state-of-the-art Argon dating techniques with previously reported Uranium-Lead dating results to determine that the volcanic activity really ramped up within 50,000 years of the Chicxulub impact. They feel that the seismic impact of the Chicxulub event was enough to shake up the Earth and increase the volcanic activity within the Deccan Traps. The Deccan Traps are certainly large enough to have released enough greenhouse gasses to have an effect on the environment.
The group concludes their study by suggesting that the mass extinction event at the end of the Mesozoic may have likely been a combination of these factors, and not necessarily solely the responsibility of the Chicxulub impact. The resulting volcanic activity may have acted as the final nail in the coffin for the dinosaurs.