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HISTORY
  Big Bang
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  The Earth
  Continents
  Ice Epochs
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  Precambrian
  Paleozoic
  Mesozoic
  Cenozoic
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Cenozoic

© 1985 by Andrew J. Morris

The Cenozoic era encompasses the past 70 million years -- right up to the present. That may seem a long time, but remember it is only about one-half of one percent of all the time since the Big Bang 15 billion years ago. The Cenozoic era is called the "Age of Mammals."

Early in the Cenozoic began another mountain building period. The Rocky Mountains, from Alaska to New Mexico, rose up during this time. By the mid-Cenozoic the weakened crust in the area of the rising mountains allowed subsurface magma to break forth into the surface -- giving rise to valcanic lava flows and eruptions. In Larimer County, Specimen Mountain erupted about 30 million years ago, spewing lava and ash over much of northern Colorado.

As the volcanic activity began to subside, the entire state of Colorado and its surrounding area began to rise. Both mountains and plains were raised up, until eventually they stood some 3,000 to 5,000 feet higher than they had been. Sediments that had all but buried the Rocky Mountains were now washed out into the plains as far as the Mississippi. Rivers began to cut down through the raised earth forming great canyons. And so eventually, the land took on the form it has today. The rivers are still cutting deeper canyons, and the mountains continue to erode, but these changes take place on a timescale that makes them almost imperceptible during the brief lifespan of man.

As our landscape was assuming its modern form, animals too were evolving into more familiar types. Early in the Cenozoic the dinosaurs still roamed the Earth, but small warmblooded mammals were evolving alongside them. About 50 million years ago the dinosaurs became extinct, leaving the thriving mammals to take their place of prominence. Plants too were evolving into new forms in the early Cenozoic, as flowering plants first appeared about this time.

It was not until very late in the Cenozoic, two to three million years ago, that anything resembling man could be found. By this time the American continents had long since separated from Europe, Asia and Africa where early man was evolving. Only in the past twenty to fifty thousand years di man come into the scene in America.

Visit our Genealogy section to find Larimer County ancestors, or see our Employment department to find a job!