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Cenozoic
("Recent Life") Era
This is the last of three geologic eras squeezed into the Phanerozoic
("Evident Life") Eon that covers the last 10% of Earth's
whole geologic history. This is the "Age of Mammals" in
which whales took over the oceans, saber-tooth cats shared the land
with elephants and giant sloths, and humans finally appeared.
The
Cenozoic period began about 65 million
years ago with the extinction of the dinosaurs
and continues through the present. The
Cenozoic is divided into just two time
periods: the Tertiary, and the Quaternary.
We can only summarize the many events
of these periods. You can learn more by
going to your library or searching the
Internet for words like "Cenozoic"
or the names of each of the periods.
The view of Earth above
is that of today. During the last 65 million years, Pangea has broken
up into the continents, and they have moved into the positions which
we see them in now. The Atlantic Ocean has opened from a narrow
valley to a vast ocean. India has moved across the Indian Ocean
and collided with Asia to make the Himalaya Mountains. North and
South America have moved westward over part of the Pacific Ocean.
The pressure has crumpled the western coasts of both continents
to form the Rocky and Andes Mountains. Part of the Pacific sea floor
has been forced into the warm interior under the American continents,
causing melting and the formation of the Cascade and Andes volcanoes
on the surface.
The
global climate has turned somewhat colder,
and the last few million years have seen
the return of giant glaciers and ice caps
to North America, Eurasia, and Antarctica.
After the disappearance
of the dinosaurs, there were suddenly many empty places on Earth
where animals could live. Mammals, which were small, mouse-like
animals at the beginning of the Cenozoic, quickly spread out, diversified
in kind, and grew in size. Soon the plains and forests of Earth
were occupied by giant rhinos and elephants, lions and saber-tooth
cats, horses and deer. The skies filled with bats and birds, and
the seas filled with whales and porpoises, as well as with fish
and octopi. There have been mass extinctions during the Cenozoic
as there were during the Mesozoic and Paleozoic, but not as many
animals and plants have disappeared.
Finally, humanity appeared
during the last two million years. In the last 10,000 years, a blink
of the eye in geologic time, humanity has spread across the lands
and seas of Earth, altering the face of Earth with cities and farms,
destroying some plants and animals and domesticating others. Humans
have become the dominant terrestrial life form: more numerous than
any other large animal, and more fearsome than the most terrible
of dinosaurs.
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