Dinosaurs Extinction

The first question that must be posed when trying to crack the mystery of the
mass extinction is to ask, throughout history were there any other occurences of
this magnitude? The answer is a resounding yes. Altogether over time there has
been about eight mass extinctions to large land dwelling vertebrates. The most
recent was about ten thousand years ago, killing most of the giant mammals like
mammoths, mastodons, super-large camels, saber-toothed tigers, and others (Bakker

428). The second question, is whether or not these mass extinctions follow a
pattern? Once again the answer is yes. Every time a mass extinction occurs on
the land ecosystem, the oceanic system is hurt. When the dinosaurs died, many
sea animals also died out (Bakker 428-430). The final question to be asked, is
when these mass extinctions occur, are both land and water animals affected, and
if so, are they affected at the same point in time? All saltwater animals
suffered, however, freshwater creatures were left unaffected. Plants on land did
suffer, but not nearly as much as the dinosaurs and other creatures that
depended on them as a food source.(Bakker 431). Since the time that the first
dinosaur was discovered, paleontologists have been pondering the demise of the
dinosaurs. Over a hundred theories have been produced to explain this mass
extinction (Psihoyos 255). The dinosaurs may have died because, "the
weather got too hot," ; "the weather got too cold," ; "the
weather got too dry," ; "the weather got too wet," ; "the
weather became too hot in the summer and too cold in the winter," ;
"the land became too hilly," ; "new kinds of plants evolved which
poisoned all the dinosaurs," ; "new kinds of insects evolved which
spread deadly diseases," ; "new kinds of mammals evolved which
competed for food," ; "new kinds of animals evolved which ate all of
the dinosaurs\' eggs," ; "a giant meteor hit the earth," ; "a
supernova exploded near the earth," ; "cosmic rays bombarded the
earth," ; or "massive volcanoes erupted all over the earth at once (Bakker

425)." Scientists\' beliefs seem to fall into two basic common positions,
the Catastrophists, and the Gradualists (Psihoyos 255). The Catastrophists
believe that a huge catastrophic event took place, killing all of the dinosaurs.

The most popular theory of the Catastrophists is the asteroid theory. An
asteroid called Chicxulub hit the earth creating a 150 mile wide crater near the

Yucatan Peninsula in Mexico. The date this asteroid hit the earth was sometime
about 65.7 million years ago, just about the time the dinosaurs died (Psihoyos

255). When this two-mile-wide asteroid hit the earth, it probably shattered and
sent tons and tons of asteroid-earth dust into the stratosphere. The lack of
light caused by the dust blocking out the sun would have caused many plants to
die out, leaving plant eating dinosaurs to die, and with no herbivores to hunt,
the carnivorous dinosaurs would die out, the domino effect (Krishtalka 19-20).

This event also would have frozen the earth, another reason why it would kill
all of the dinosaurs. No one can prove this theory, but it is one of the most
recent theories among scientists these days, as to what killed off all of the
dinosaurs. The dinosaurs were around for roughly 140 million years. They were
the ruling beasts of the earth for this whole period. Then, 65 million years ago
the dinosaurs just all died. None flying through the air, none swimming in the
water, none walking on land. They were all just gone. "The death of the
dinosaurs was the biggest mass extinction in the history of the earth (Bates

8-10)." The first clue that led scientists to the asteroid theory was the
finding of a thin layer of clay in the ground. In 1978 Walter Alvarez, a

Professor of geology from Berkeley, California, was driving up out of a deep
limestone gorge behind Gubbio, Italy, when he noticed something strange.

Limestone was formed when little prehistoric sea animals called forams died and
fell to the bottom of the ocean to form rock. When he was driving along he side
of this gorge he noticed that right at one point, all of the forams were gone.

This also happened to be a point in the ground right at 65 million years, right
about the time the dinosaurs died. Another strange thing Alvarez noticed was
that right in between the forams and the above rock was a thin layer of clay. He
felt that the clay might be important so he chipped a piece off, and hid it
away. Upon his arrival