Extinction of Dinosaurs
Two-hundred and thirty million years ago the first dinosaur-like
creature roamed the earth. Within five million years it could be considered a
dinosaur. They were soon at the top of the food chain. They populated every
continent. Then 65 million years ago they vanished. The most powerful
creatures ever to live on earth had become extinct.
Dinosaurs were not the only victims of this "mass extinction." There
were many other species that were killed off. During what is known as the K-T
extinction (K stands for Cretaceous, T stands for Tertiary), many species and
families became extinct. These include all marine reptiles such as plesiosaurs,
mosasaurs, ichthyosaurs, and ammonites, swimming and flying reptiles, sea
crocodiles, and foraminifera. In addition to that there were many bony fish,
sponges, snails, clams, and sea urchins became extinct.
Paleontologists have proposed scenarios that could have caused these
extinctions. One such scenario involves the growing number of small mammals
which ate dinosaur eggs, and therefore caused the dinosaurs' birth rate to drop.
The birth rate became smaller than the death rate and the dinosaurs died out.
This, however, is not a plausible scenario. This would only account for the
dinosaurs, but not all the other creatures of that time. Paleontologists needed
to come up with a more plausible and devastating theory that would include the
other creatures that died out 65 million years ago.
There have been several major theories that have come about that can all
be substantiated. Any one of these events, theorized by paleontologists, could
have brought an end to the dinosaurs and all the other species that died with
them. Since there are many theories about this I will not write about them all.
I have chosen the theory about death by Cosmic Collision (an asteroid).
In 1980 Luis Alvarez and John Sepkowski Jr., famous geologists, blamed
the extinction of the dinosaurs on a large celestial body which hit the Earth 65