Geoscience Reference
In-Depth Information
boundary, with dramatic changes in oxygen and carbon levels before and after, indicating a dramatic rise in
global temperature followed by a precipitous drop. But taken together, these factors do not fully explain the
magnitude of the greatest extinction event in fossil history.
DIMETRODON
The sandstone cliffs of Prince Edward Island are a vivid reminder of the desert conditions that prevailed during the
Permian Age.
This great dying was a dividing line in the classification of life on Earth. It was the end of the Paleozoic, or
“the era of old life,” and the beginning of the Mesozoic, or “the era of middle animals.” The Mesozoic itself
was divided into three major periods—Triassic, Jurassic, and Cretaceous—encompassing the rise, flourishing,
and ultimate fall of the dominant reptile group known as the dinosaurs.
THIS PERIOD OF
change in life on Earth was marked geologically by the breakup of Pangaea and the creation of
the present-day Atlantic Ocean. In the Late Triassic (225 million years ago), the Earth's crust weakened and
