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Why are dinosaurs extinct?

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Quick Answer

There are a few well-researched theories about why dinosaurs are extinct; one of the most prominent theories hypothesizes that a massive asteroid impact killed off the dinosaurs. Another states that heavy volcanic eruptions across the Earth may have been responsible.

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Full Answer

The asteroid-impact theory states that a large asteroid hit the earth 65 million years ago and killed not only the dinosaurs but many other species as well. Once the asteroid hit, scientists theorize that dust and debris flew into the atmosphere, preventing the sun from reaching plants. Plants withered away, resulting in the extinction of plant-eating dinosaurs. This resulted in the extinction of carnivorous dinosaurs, which depended on plant-eating dinosaurs for food. Furthermore, this dust changed the world's climate for several years, making it impossible for some species to survive.

This theory is corroborated by a huge impact crater located at the Yucatan Peninsula. Also, there is a layer of iridium in the rock dating back 65 million years, which corresponds to the time of extinction. Iridium is rare except in asteroids and the Earth's core. This 65-million-year-old layer is found all over the world and is too abundant to be natural, suggesting that it is from an asteroid that impacted the Earth.

Another theory relating to this iridium layer is that volcanic eruptions caused the extinction of the dinosaurs. Iridium is also abundant in the Earth's core and magma, and massive eruptions and lava flow could have spread the iridium worldwide.

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