|Probably the most famous extinction throughout history was the end of the dinosaurs about
65 million years ago. Not only did the dinosaurs die out, whatever caused it also caused the death of around
70% of all species on Earth. Scientists have come up with some theories on why this mass extinction occurred.
Two of the most widely known theories are the asteroid impact and the volcano/greenhouse gas theory.
Could a giant asteroid have crashed into the earth millions of years ago and
wiped out the dinosaurs? There is evidence of a large crater that dates back about
65 million years ago. If this massive asteroid had collided with the earth, it would
have thrown billions of dust and debris into the atmosphere, blocking out the sun,
and causing a Nuclear Winter. Without sunlight, plants would stop growing and eventually
die. If the herbivores had no plant food, then they would have starved, and so the
carnivores would have had no meat to fill their stomachs with, thus causing their
demise as well. In addition, the loss of the sun would have caused temperatures to
plummet to below freezing, which also helped with the demise of the dinosaurs.
Volcano/Greenhouse Gas Theory
This theory was created by a gentleman named Dewey McLean. He proposed that a large volcanic eruption could have filled the atmosphere with carbon dioxide and allowed for a large rise in temperature. According to the theory, the carbon dioxide would have let the sun's radiation enter the atmosphere, but none to escape. This rise in temperature would have caused some species to become sterile. Infertility could have caused the extinction of the dinosaurs as well as mammals such as the mastodon and the saber-toothed tiger. A rise in temperature might have killed plankton in the sea, disrupting food chains and making the carbon dioxide factor worse because of its job converting it to oxygen. Without clean air to breathe, many animals would die.