Strong evidence suggests that a huge asteroid impact caused the mass dinosaur extinction 66 million years ago. During Beta testing articles may only be saved for seven days. Create a list of articles to read later. You will be able to access your list from any article in Discover. The end of the Cretaceous Period saw one of the most dramatic mass extinctions Earth has ever seen. Find out what brought about the end of the dinosaurs and many other animals too.
The fossil record shows that for the first million years of their existence, dinosaurs took on a huge variety of forms as the environment changed and new species evolved that were suited to these new conditions. Dinosaurs that failed to adapt went extinct. But then 66 million years ago, over a relatively short time, dinosaurs disappeared completely except for birds.
Many other animals also died out, including pterosaurs, large marine reptiles, and ammonites. Although the number of dinosaur species was already declining, this suggests a sudden catastrophic event sealed their fate - something that caused unfavourable changes to the environment to occur more quickly than dinosaurs and other creatures could adapt.
The exact nature of this catastrophic event is still open to scientific debate. Evidence suggests an asteroid impact was the main culprit. Volcanic eruptions that caused large-scale climate change may also have been involved, together with more gradual changes to Earth's climate that happened over millions of years. Animals Wild Cities This wild African cat has adapted to life in a big city Caracals have learned to hunt around the urban edges of Cape Town, though the predator faces many threats, such as getting hit by cars.
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He and his son, noted geologist Walter Alvarez, were conducting research in Italy when they discovered a centimeter-thick layer of iridium-enriched clay at the K-T boundary. Iridium is rare on earth, but more common in space.
The Alvarezes published their findings in , postulating that the thin layer of iridium was deposited following the impact of a large meteor, comet or asteroid with the earth. At the time, the Alvarez theory was so far removed from prevailing hypotheses that it was ridiculed. Slowly, though, other scientists began finding iridium evidence at various places around the globe that corroborated the Alvarez theory.
There was, however, no smoking gun in the form of an impact site. The Chicxulub Crater, as it was dubbed, was named for a nearby village. Scientists believe the bolide that formed it was roughly 6 miles in diameter, struck the earth at 40, miles per hour and released 2 million times more energy than the most powerful nuclear bomb ever detonated.
Miles-high tsunamis would have washed over the continents, drowning many forms of life. Shock waves would have triggered earthquakes and volcanic eruptions. The resulting darkness could have lasted for months, possibly years. Many dinosaurs would have died within weeks. The carnivores who feasted on the herbivores would have died a month or two later. Overall, the loss of biodiversity would have been tremendous. Only small scavenging mammals that could burrow into the ground and eat whatever remained would have survived.
The iridium layer plus the Chicxulub Crater were evidence enough to convince many scientists that the bolide impact theory was credible. It explained much of what previous theories could not. Paleontology remains a competitive discipline even though its central mystery appears to have been solved. Agreement over dinosaur extinction is far from unanimous, and fossils continue to be found that add to the body of knowledge about how the dinosaurs lived and died.
Only recently have birds been identified as descendants of the dinosaurs, and theories regarding dinosaur intelligence and behavior continue to change. The climate change theory still holds sway over some scientists, who refute that the Chicxulub impact was the sole cause of the extinction.
Evidence from the million-year-old lava flows in India hint that a giant, gaseous volcanic plume might have initiated global climate change that threatened the dinosaurs. But if you see something that doesn't look right, click here to contact us! Subscribe for fascinating stories connecting the past to the present.
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