Geologic Timeline

Oldest Rocks and Oldest Fossilized Cells

1 CE

4.6 billion to 542 million years ago
The earth had a harsh environment, with a weak atmosphere and volcanoes constantly erupting. It had simple oceanic life and was divided into the Hadean, Archean, and Proterozoic eons.

Trilobites

2

542 to 488 million years ago
Multicellular life in the ocean had become very widespread. Trilobites were the dominant ocean species. The atmosphere changed to have more oxygen, much like our current atmosphere today.

First fish and mass extinction

3

488 to 444 million years ago
The number of trilobites has dropped considerably, but invertebrates are still the dominant life form. The first vertebrates appear as well, but an extinction event wipes of 60% of all life forms on earth.

First Plants

4

444 to 416 million years ago
Small mossy plants had begun to grow in the coastal regions. The Eurypterid, an arthropod, had also begun to grow in numbers. These arthropods were the first ever on land.

First Grasses and Mass Extinction

5

416 to 359 million years ago
Earth was covered with horsetails, ferns, and seeds of varying kinds. Fish had also become more varied and large in population, Fish also began to develop legs, signifying the change to living on land. Another extinction event occurred, killing off 70% of species.

First Insects, Amphibians, and Reptiles

6

359 to 318 million years ago
Many different land life forms had appeared, due to the continents being bunched together. The landscape was mostly wet and swampy, and massive coal beds had also formed during this period.

Mass extinction

7

299 to 251 million years ago
Earth’s continents had come together as Pangaea. There was a large diversity in environments, climate, and life. However, due to rapidly changing climate, 90-96% of all life was extinct by the end of this period.

First dinosaurs, mammals, and a mass extinction

8

251 to 65.5 million years ago
This era was divided into 3 periods, the Cretaceous, Jurassic, and Triassic periods. Dinosaurs had evolved and were the dominant life form, but flowering plants and mammals had also shown up. A mass extinction took place due to a meteorite crashing into earth, blocking out the sun. Somehow, mammals and plants survived the event.

First Birds

9

65.5 to 1.8 million years ago
There was a large diversity of life, ranging from mammals, birds, fish and insects. The climate had mostly tropical forest, but the planet had begun to cool, causing grasslands and plains to form. This era had been divided into 5 epochs including the Paleocene, Eocene, Oligocene, Miocene, and Pliocene.

First Humans

10

1.8 million years ago to now
Two epochs have made up this era, the Pleistocene and Holocene. The continents have moved into their current position, causing glaciers to form in the north and south poles. Humans have appeared and begun to create mass and complex societies, creating dominance over other life forms. At the beginning of this era, woolly mammoths and other large mammals had appeared, but some have gone extinct.