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The Cenozoic era is the most recent era in Earth history. It started
about 65 million years ago and continues through the present day.
The Cenozoic is divided into smaller segments called epochs which
are, from oldest to youngest, the Paleocene, Eocene, Oligocene,
Miocene, Pliocene, Pleistocene, and Holocene. These epochs have
been combined to create larger periods. Some scientists create two
periods in the Cenozoic called the Tertiary
and the Quaternary. In this case,
the Tertiary is made up of the epochs from the Paleocene through
the Pliocene (and is divided into the Paleogene
and Neogene), and the Quaternary includes
the Pleistocene and Holocene epochs.
Much of what we see in terms of topography today has been formed
in the Cenozoic for the simple reason that many older features have
been changed or erased from the surface. This is different from
rock ages, though. For example, we find truly ancient Precambrian
rocks in the Rocky
Mountains, but the character of the mountains themselves is
relatively young, having developed mostly within the last 60 million
years. Many of the features listed on this Web site have a Cenozoic
component associated with them, whether it is in terms of rock age
(the Coastal Plain,
for example), topographic development (the Rockies, again), or activity
(the San Andreas Fault
and the Cascades).
Features related to the Cenozoic include the following:
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