Shop Windows to the Universe

Science, Evolution, and Creationism, by the National Academies, focuses on teaching evolution in today's classrooms. Check out the other publications in our online store.

An Overview of Earth History

The Earth has been around for approximately four and a half billion years! The geologic time scale is the timeline that describes all this time.

Scientists have found rocks that formed during every time period of Earth's history! In sedimentary rocks, they have found millions of fossils and clues to past environment. Take a look at the stories below to discover how some scientists are discovering more about our planet's past.


Missing Link Between Whales and Four-Footed Ancestors Discovered
Did Life First Form in a Mica Sandwich at the Bottom of an Ancient Sea?
Using Leaves From the Past to Tell the Future!
Digging Woolly Rhinos
Did T-Rex Have a Plant-Eating Relative?
Diamonds are Ancient History
Geologic Findings Undermine Theories of Permian Mass Extinction Timing
Old Rocks Give New Clues about Ancient Earth
Evolution Hits the Beach - streaming RealVideo (1 min. 7 sec.) from NSF
The History of the Universe in 60 Seconds or Less - Dr. Eric Schulman - streaming RealVideo (1 min. 16 sec.) from NSF

The table below provides a brief overview of Earth history. M stands for millions of years. The present time is at the top of the table and ancient time is at the bottom of the table.

Where the continents were Eras Approximate age (in years) Subdivision Approximate duration (in years) Notes

Earth, 20 M ago

CENOZOIC 10,000
2 M
5 M
24 M
37 M
57 M
66 M
HOLOCENE
PLEISTOCENE
PLIOCENE
MIOCENE
OLIGOCENE
EOCENE
PALEOCENE
3 M
19 M
13 M
20 M
9 M
The beginning of the Eocene was a period when the Earth was very hot, with palm trees and alligators at the north pole. Earth but cooled by the start of the Quaternary. This period relates to today's concern about global warming. Homo sapiens evolved and Ice Ages occures towards the end of this time. The Little Ice Age (which is not a true ice age) occured a few hundred years ago.

Earth, 190 M ago

MESOZOIC 144 M
208 M
245 M
CRETACEOUS
JURASSIC
TRIASSIC
78 M
64 M
37 M
The Mesozoic is the period in which the dinosaurs lived, and its end was marked by the K-T extinction. This extinction event dramatically changed the Earth's flora and fauna, and its causes are still being investigated by scientists around the world. During the Mesozoic, the giant continent Pangaea broke apart into the continents we have today.

Earth, 400 M ago

PALEOZOIC 286 M
360 M
408 M
438 M
505 M
570 M
PERMIAN
CARBONIFEROUS
DEVONIAN
SILURIAN
ORDOVICIAN
CAMBRIAN
41 M
74 M
48 M
30 M
67 M
65 M
The Cambrian period, at the beginning of the Paleozoic, was the first time that multicellular life forms florished on Earth. By the end of the Paleozoic, and beginning of the Mesozoic, all the continents of the Earth came together to form the giant continent called PANGAEA and dinosaurs began to roam on land.

Earth, 540 M ago (end of Precambrian)

PRECAMBRIAN 2800 M
4800 M
PROTEROZOIC
ARCHEAN
2300 M
2000 M
This period is about 5 times as long as the Paleozoic and Mesozoic combined, a very long time. Less is known about it than the younger time periods. The oldest fossils are of bacteria/archaea dating from 3000 M. The oldest rock is dated at 3800 M. The Earth is thought to be 4600 M years old.

The Mystery of Mass Extinction is No Longer Murky

Fossil Record Suggests Insect Assaults Foliage May Increase with Warming Globe

Giant Fossil Frog Found in Madagascar

"Frogantuan" - A Podcast about Giant Fossil Frogs

Last modified August 23, 2009 by Jennifer Bergman.

Shop Windows to the Universe Science Store!

Learn about Earth and space science, and have fun while doing it! The games section of our online store includes a climate change card game and the Traveling Nitrogen game!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

What Is a Fossil?

Fossils are evidence of what life was like long ago. The oldest fossils are over three billion years old and the youngest fossils are about 10,000 years old. Scientists that study fossils know that creatures...more

Finding the Four-Footed Ancestors of Whales

Scientists have known for a long time that whales, the largest marine mammals, have distant relatives that lived on land millions of years ago. A team of scientists has been searching for fossils to better...more

Did Life First Develop in a Mica Sandwich at the Bottom of a Primordial Sea?

Earth's first life form may have developed between the layers of a chunk of mica sitting like a multilayered sandwich in primordial waters, according to a new hypothesis. The mica hypothesis, which was...more

Leaves As Old As Dinosaurs!

Wonder why you never see a dinosaur in your yard? Well, they are extinct of course! So, there are no more of them living on Earth. Dinosaurs became extinct 65 million years ago. They were not the only...more

Digging Woolly Rhinos!

Scientists in England have found some old bones! They found the fossil bones of an ancient woolly rhino that have been protected within rocks for thousands of years. Today, rhinos live in warm places...more

Geologic Findings Undermine Theories of Permian Mass Extinction Timing

You probably know that dinosaurs are extinct. That means they are no longer alive today. Millions of years before the dinosaurs roamed the Earth, there were plants and other animals alive. There were fish,...more

The Little Ice Age

From about 1250 to 1850 temperatures were a bit colder than usual in most parts of the world. This time is called the Little Ice Age. During the Little Ice Age, the average temperature of the planet was...more

K-T Extinction (Why Did the Dinosaurs Go Extinct?)

Why did the dinosaurs go extinct? No one knows for sure, but there are some explanations that seem to make sense. At the time the dinosaurs and lots of other species died out (which is sometimes called...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA