Characteristics of the Cenozoic Click on image for full size (110) L.Gardiner/Windows to the Universe

Time:

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!)

Paleogeography:

• 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!

Climate:

• 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.

Characteristics of the Cenozoic Click on image for full size (110) L.Gardiner/Windows to the Universe

Time:

65 million years ago to today (and continuing!)
(See the geologic timescale!)

Paleogeography:

• 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.

Climate:

• Early Cenozoic climate was warm and humid and the climate cooled gradually during the Cenozoic.
• During the past two million years, Earth's climate has cooled and warmed over and over again. The cool times are called Ice Ages because large amounts of ice formed on land. The last time that these sheets of ice were very large was 20,000 years ago. Most of the sheets of ice melted by about 10,000 years ago.
• Whenever 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.

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 was well adapted to the cooler climates of the late 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. 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.

Characteristics of the Cenozoic Click on image for full size (110) L.Gardiner/Windows to the Universe

Time:

65 million years ago to today (and continuing!)
(See the geologic timescale!)

Paleogeography:

• The Atlantic Ocean is still growing wider.
• India used to be an island, but it collided with Asia during the Cenozoic. This caused the Himalayan Mountains to form. India is still pushing against Asia, causing the mountains to grow even larger!
• Africa pushed into Europe forming the Alps.
• In North America, the Rocky Mountains formed.
• Earth's plates still move around because of plate tectonics!

Climate:

• The climate cooled gradually over most of the Cenozoic.
• During the past two million years, Earth's climate has cooled and warmed over and over again. The cool times are called Ice Ages because large amounts of ice formed on land. The last time that these sheets of ice were very large was 20,000 years ago. Most of the sheets of ice melted by about 10,000 years ago.
• Whenever climate cooled and ice sheets formed on land, there was less water left in the oceans, so the sea level was lower. Sometimes lower sea level caused land that is usually underwater to be above water and continents were connected that were usually separated by oceans. This allowed animals to walk to other continents.

Evolutionary Events:

• There are many more mammals during the Cenozoic! 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 for the first time large areas of grassy fields developed on the land.
• Horses and other species of grazing animals evolved that liked to eat the grass. The first horses were small, about the size of a labrador retriever.
• Thousands of fossils of ancient humans and their ancestors have been found. The oldest fossil of a human ancestor is more than 6 million years old. Fossils that are very similar to modern humans are called Homo sapiens. Fossils of Homo sapiens are as much as 400,000 years old.