Happenings During the Cenozoic (65 Million Years Ago to Present)


65 million years ago to today (and continuing!)
Geologic periods (divisions): Tertiary and Quaternary (the past 2 million years)
The Tertiary period is divided into: Paleocene, Eocene, Oligocene, Miocene and Pliocene (from oldest to youngest)
The Quaternary period is divided into: Pleistocene and Holocene
(See the geologic timescale!)


  • The Atlantic Ocean continues to widen as new ocean crust is formed at the Mid Atlantic Ridge.
  • India collided with the Asian continent forming the Himalayan Mountains which continue to grow higher today.
  • The African plate pushed into Europe forming the Alps.
  • In North America, the Rocky Mountains formed and the Colorado Plateau was uplifted. When the land of the Plateau uplifted, rivers flowing over it were able to carve deep canyons. For example, the Colorado River carved the Grand Canyon as it flowed across the plateau over 20 million years.
  • Earth's tectonic plates continue to move today by a process called plate tectonics!


  • Early Cenozoic climate was warm and humid, much like the end of the Mesozoic and the climate cooled gradually during the Cenozoic.
  • Ice Ages occurred during the past two million years with repeated forming and melting of glaciers and ice sheets called glaciations. The most recent glaciation occurred about 20,000 years ago. Most of the ice sheets that formed during this glaciation melted by about 10,000 years ago.
  • Whenever Earth's climate cooled and ice sheets formed on land, there was less water left in the oceans, thus lower sea level. Sometimes lower sea level caused land that is usually underwater to connect continents. These areas of land, called land bridges, allowed animals to migrate to other continents.
  • Just several hundred years ago a period of warming (called the Medieval Warm Period) and cooling (called the Little Ice Age) affected people and other living things.

Evolutionary Events:

  • Mammals, which had been small and few during the Mesozoic, became more diverse. New mammal species evolved and were able to live in areas and eat foods that had been used by dinosaurs during the Mesozoic.
  • Grass evolved and flourished in the cooler climates of the later parts of the Cenozoic.
  • Horses and other species of grazing animals evolved and ate the newly-evolved grass. The first horses were small, about the size of a labrador retriever.
  • Modern humans and their recent ancestors are called hominids. Thousands of fossils of hominids have been found; the oldest is more than 6 million years old. One early hominid was Australopithecus. The first Australopithecus skeleton found was that of a woman who had been about 25 years old at the time she died. The researchers who found the fossils of this Australopithecus skeleton called her "Lucy". She would have been only three and a half feet tall. Fossils of hominids that are similar to modern humans are called Homo sapiens. Fossils of Homo sapiens are as much as 400,000 years old.
Last modified June 1, 2005 by Lisa Gardiner.

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