The World of Dinosaurs
The Cretaceous Period
The Cretaceous period takes its name from the Latin 'creta' meaning chalk, which
was deposited towards the latter half of the period. It is the last period
of the Mesozoic era. During this period the first seed plants developed
and the dinosaurs reached their peak before they became extinct towards the
end of the Cretaceous.
During the early Cretaceous the climate was sub-tropical with wet and dry seasons. By the end of the Cretaceous the world began to look and feel much more like it does today.
Towards the end of the Cretaceous Period about 65 million years ago, when they were thriving,
dinosaurs suddenly became extinct. This has caused endless speculation and
there have been many theories put forward to explain this sudden demise.
The two most probable theories are the Gradualistic and Catastrophic Theories,
none of which have been proven, and neither fully explain why some types of animals
survived yet others did not.
The Gradualistic theory is based on slow climate change.
It is known that the climate towards the end of the Cretaceous was cooling
and there were numerous volcanic eruptions that could have caused severe
environmental changes. These changes would lead to a decline in the numbers
and diversity of the dinosaurs eventually making them extinct.
The Catastrophic theory is more spectacular. There is evidence that towards the
end of the Cretaceous there was an asteroid impact that would have
been the catalyst for the earth's eco system to change dramatically enough to wipe out the dinosaurs.
Many animals survived this extinction including mammals and types of reptiles. The only
dinosaurs to survive were the birds descended from the theropod line.
