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Introduction
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Legend and Rock Ages
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Cenozoic Rocks - 66 million years ago to the present

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: