The end of the dinosaurs is one of the greatest mysteries of paleontology. The leading theory of their extinction involves a massive meteor impact, possibly the one that created the Chicxulub crater in Mexico. Alternative theories include multiple global impacts, a sudden change in the sea level and a worldwide increase in volcanic activity that drastically altered the atmosphere and global climate.
According to the Alvarez Hypothesis, the extinction of the dinosaurs occurred as a result of a massive comet or meteor impact. One of the major pieces of evidence that supports this hypothesis is a layer of iridium found in clay that marks the boundary between the Cretaceous and Paleogene periods, which is when the dinosaurs went extinct. In the 1990s, geologists discovered a 112-mile-wide crater just off the Yucatan peninsula that provided evidence of just such a massive impact occurring around the same time as the extinction.
A few questions remain unanswered, however. A single impact would have had devastating effects on the environment, but most of the dangerous changes, such as an increase in acid rain, would only last a decade or two after the event. The dinosaurs' extinction occurred over a more extended period of time, bringing up the possibility that multiple impacts, possibly including the one that caused the Shiva crater in India, may have contributed to the extinction.Learn More
True dinosaurs were not swimmers. There were a number of very large aquatic reptiles that lived during the age of the dinosaur, but they were not technically dinosaurs. These creatures belonged to one of several other groups, such as ichthyosaurs, plesiosaurs and mosasaurs, which were types of marine reptiles.Full Answer >
There are multiple theories as to why dinosaurs died out, such as asteroid impact, volcanic activity, and climate change. There are many theories because none has been proven to be 100 percent certain as the reason for the dinosaurs’ demise.Full Answer >
The first true dinosaurs first appeared about 230 million years ago. The first dinosaur fossils are distinguished from those of their reptile ancestors by their more upright stance, with legs directly beneath the body instead of splayed to the side, as with other reptiles. The earliest dinosaur fossils were found in South America, although a December 2012 fossil discovery in southern Africa casts some doubt on a South American origin.Full Answer >
Dinosaurs became extinct about 65 million years ago. This extinction event occurred between the Cretaceous and Tertiary periods and wiped out about 50 percent of all other organisms then living on the planet.Full Answer >