Freeway - Earth's Largest Extinctions

Earth's Largest Extinctions

Most people have heard of the asteroid that killed the dinosaurs about 65 million years ago. The dinosaurs aren't the only ones who have become extinct, in fact 99.9 % of all species who have ever lived on our planet are now extinct. But what are these extinctions?

In this article you will be able to read about some of the largest extinctions that have ever stroke the earth and it isn't only asteroids that are the cause.

Ordovician-Silurian Extinction

The Ordovician-Silurian Extinction occurred about 439 million years ago. It was caused by sea levels dropping as glaciers were forming and then sea level rising when the glaciers melted. About 85% of the species at that time became extinct because of this happening.

Permian-Triassic Extinction

This extinction is the worst of earth's mass extinctions. It took place about 253 million years ago and killed 95% of all living species. Scientists believe it was an asteroid that hit the earth but no evidence has been found. Another theory is sea bottom volcano activity which would have caused a lack of oxygen in the oceans.

End Triassic Extinction

The End Triassic Extinction is most likely caused by massive volcano eruptions situated were the Atlantic Ocean is today. These eruptions may have created a deadly global warming which killed approximately 75% of all living species. This happened about 213 million years ago.

Cretaceous-Tertiary Extinction

At the end of the cretaceous period, about 65 million years ago, a large mass extinction took place. An asteroid six miles in diameter is believed to have hit the earth and created the Chicxulub crater. This crater is situated on the Yucatan Peninsula beneath the Gulf of Mexico.
The asteroid threw dust into the atmosphere which blocked out the sunlight, causing 85% of the earth's species to die. The dinosaurs included.

Species made extinct by humans

Since humans started to colonize islands about 2000 years ago 20% of all bird species have disappeared. Habitat destructions like the rain forest devastation causes many species to disappear.
Animals and parasites have been brought to isolated islands causing competition with the native animals which often leads to their extinction.
Soon we even might make ourselves disappear. If someone starts a nuclear war we could get the same effects as from an asteroid impact; dust in the atmosphere, no sunlight and temperatures below -40 degrees Celsius.