Geologic Timeline

Precambrian Time

This is the time where Earth formed. The atmosphere, organisms, continents, and oceans also formed and evolved.

Precambrian Time

4,560,000,000 BC - 542,000,000 BC

Earth - Earth formed from dust, rock, and ice in space.
The atmosphere of Earth started out as a bunch of gases. As the earth cooled, the water vapor turned into rain and formed the oceans. Continents formed in the oceans and split apart due to the tectonic plates.

Life - Prokaryotes, single-celled organisms without a nuclei, and eukaryotes, single-celled organisms with nuclei, formed in the ocean. Cyanobacteria, a prokaryote, used photosynthesis to turn carbon dioxide into food. During this process, they released oxygen and changed the Earth's atmoshpere to mostly oxygen. Animals evolved very late in the Precambrian Time. They had soft bodies so they left some, but not many, fossils.

Paleozoic Era

During this time, many organisms evolve and life on Earth really gets going. Much of the life ends with a mass extinction due to major changes in the environment.

Cambrian Period

542,000,000 BC - 488,000,000 BC

Earth - Rodinia broke up into smaller pieces.

Life - The animals in this period were the first to have hard parts such as shells and exoskeletons. They left behind a well known fossil, the Burgess shale, in the Canadian Rockies. These organisms were all water dwellers.

Ordovician Period

488,000,000 BC - 444,000,000 BC

Earth - Gondwana moved south.

Life - Bryozoans appeared and brachiopods left behind many fossils during this period. Jawless fishes and land plants evolved. Land plants helped add oxygen into the atmoshpere. The mass extinction at the end of this period was caused by an ice age or volcanic eruptions.

Silurian Period

444,000,000 BC - 416,000,000 BC

Earth - Sea levels rised and flooded parts of Gondwana with shallow water, where barrier reefs formed.

Life - Fish and reefs evolved in the oceans. Land plants continued to spread and later, land animals evolved.

Devonian Period

416,000,000 BC - 359,000,000 BC

Earth - Two continents, Gondwana in the south and Laurasia in the north, inhabit Earth.

Life - In the seas reefs, corals, sharks and new jawed fishes appeared. On land, a forest spread with new land plants in it. Amphibians evolved and they didn't have many predators, so they spread rapidly. Two mass extinctions wiped out some of the ocean animals.

Carboniferous Period

359,000,000 BC - 299,000,000 BC

Earth - The Appalachian Mountains formed because the continents collided with each other. Some parts of the continents flooded again and calcium carbonate was deposited in the areas by reef-building organisms.

Life - Reptiles evolved and swamps developed in forests. When the animals and plants in the swamp died, coal formed from their remains.

Permian Period

299,000,000 BC - 251,000,000 BC

Earth - Big glaciers formed in southern Pangea. As Pangea moved north, the glaciers melted. Areas that had no moisture formed deserts and the shallow seas evaporated.

Life - New types of animals continued to evolve such as mammal-like reptiles. The Permian Period ended with a mass extinction. It was caused by either volcanic eruptions, an asteroid, or the clashing of the continents that formed Pangea.

Mesozoic Era

Reptiles thrived

Triassic Period

251,000,000 BC - 200,000,000 BC

Earth - Pangea formed and went through the seasons. At the end of the Triassic Period, Pangea started to break up.

Life - Mammals and gymnosperms evolved.

Jurassic Period

200,000,000 BC - 145,000,000 BC

Earth - North America got new mountains because the North American plate moved over the Oceanic plate.

Life - Reptiles with wings evolved. They were called pterosaurs.

Cretaceous Period

145,000,000 BC - 65,000,000 BC

Earth - Large coal deposits in Canada and western United States were formed by swamps.

Life - Angiosperms evolved. They make seeds, but they don't have an outer covering. Scientists suspect that a large mateorite struck the Earth and caused another mass extinction.

Cenozoic Era

Mammals thrived.

Tertiary Period

65,000,000 BC - 18,000,000 BC

Earth - The Rockies, the Alps, and the Himalayas formed.

Life - Mammals evolved even more. They adapted to their environments, evolving new limbs and teeth.

Quarternary Period

18,000,000 BC - Present

Earth - Continental glaciers covered the northern hemisphere because it was cold enough.

Life - Mammals evolved to be large, but they all went extinct. Causes may have been humans hunting them.