by Kessie Carroll

Created on: April 04, 2009

Fact: Dinosaurs are extinct.

Beyond that, it's all guesswork. Why did they all die, and yet other species survived? Why only this particular group of animals?

The most popular theory is the asteroid. It's featured in cartoons and movies, because hey, a giant ball of fire hitting the earth and killing everything is visually impressive.

The trouble is, recent findings from paleontologist Gerta Keller show that the asteroid crater is smaller than originally believed, and apparently it hit the earth 300,000 years earlier than the Big Dinosaur Extinction. So it doesn't explain everything.

Another theory states that something caused the earth to tilt and wobble on its axis, disrupting the weather patterns and causing extreme ice ages. If this happened quickly, it might explain why we sometimes find mammoths completely preserved in glaciers, some with the grass they were eating still in their mouths.

Such wobbling might have also caused extreme volcanic eruptions. When Mt. Pinatubo erupted in 1991, it ejected so much ash into the atmosphere that it lowered the global tempurature by a whole degree or two. And that was only one volcano. If, for instance, the entire Ring of Fire around the Pacific Ocean erupted, it would foul the atmosphere so much that it could kill most of the life on earth.

During an Ice Age, when the polar ice caps expanded and the ocean levels dropped, land bridges between the continents were exposed and various animals could travel to new places. Scientists speculate that this is how new diseases may have been transmitted, wiping out whole dinosaur populations in a short period of time.

Another, lesser-known theory is that a world-wide flood covered the earth and killed most life. It is true that in order for fossils to form, they require rapid burial and lots of water, so this theory seems to explain the plentiful fossils found worldwide.

The flood story is accompanied by volcanic eruptions, splits in the earth's crusts, and a change in the earth's tilt, all at the same time. If such a catastrophe really happened, it would leave all the evidence in the rock layers that so puzzle scientists: fossils, the rare element iridium, and evidence of destructive ice ages.

There are as many extinction theories as there are scientists, and each scientist fiercely defends their own theory. But all we have are the facts: dinosaurs are dead and there's lots of fossils of them. From those facts, everyone must draw their own conclusions.

References:
http://www.cnn.com/2004/TECH/ science/03/02/coolsc.dinosaurs.extinction/index.html
http://urbanext.illinois.edu/animals/dinosaurs.html
h ttp://www.answersingenesis.org/articles/nab/what-hap pened-to-the-dinosaurs

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