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Period: 541 BCE to 252 BCE
Paleozoic Era
It began 541 million years ago with the Cambrian explosion, an extraordinary diversification of marine animals, and ended about 252 million years ago with the end-Permian extinction, the greatest extinction event in Earth history. -
Period: 541 BCE to 485 BCE
Cambrian Period
The Cambrian period, part of the Paleozoic era, produced the most intense burst of evolution ever known. -
520 BCE
All major animal phyla started appearing in the fossil record.
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Period: 485 BCE to 443 BCE
Ordovician period
Ordovician Period, in geologic time, the second period of the Paleozoic Era. It began 485.4 million years ago, following the Cambrian Period, and ended 443.8 million years ago, when the Silurian Period began -
465 BCE
The Ordovician Period ushered in significant changes in plate tectonics, climate, and biological systems. Rapid seafloor spreading at oceanic ridges fostered some of the highest global sea levels in the Phanerozoic Eon.
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Period: 443 BCE to 416 BCE
Silurian Period
The Silurian Period occurred from 443 million to 416 million years ago. It was the third period in the Paleozoic Era. It followed the Ordovician Period and preceded the Devonian Period. During this time, continental landmasses were low and sea levels were rising. -
424 BCE
Possibly the most remarkable biological event during the Silurian was the evolution and diversification of fish.
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Period: 419 BCE to 358 BCE
Devonian Period
Devonian Period, in geologic time, an interval of the Paleozoic Era that follows the Silurian Period and precedes the Carboniferous Period, spanning between about 419.2 million and 358.9 million years ago. Late in the period the first four-legged amphibians appeared, indicating the colonization of land by vertebrates. -
385 BCE
During the Devonian, two major animal groups colonized the land.
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Period: 360 BCE to 300 BCE
Carboniferous Period
The Carboniferous period, part of the late Paleozoic era, takes its name from large underground coal deposits that date to it. Formed from prehistoric vegetation, the majority of these deposits are found in parts of Europe, North America, and Asia that were lush, tropically located regions during the Carboniferous. -
320 BCE
The later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea.
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Period: 298 BCE to 252 BCE
Permian Period
The Permian period, which ended in the largest mass extinction the Earth has ever known, began about 299 million years ago. The emerging supercontinent of Pangaea presented severe extremes of climate and environment due to its vast size. The south was cold and arid, with much of the region frozen under ice caps. -
267 BCE
During the Permian Period, Earth's crustal plates formed a single, massive continent called Pangaea.
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Period: 252 BCE to 66 BCE
Mesozoic Era
During the Mesozoic era, life diversified rapidly and giant reptiles, dinosaurs and other monstrous beasts roamed the Earth. -
Period: 252 BCE to 201 BCE
Triassic Period
he Triassic Period is approximately 51 million years of Earth history, from 201–252 million years ago. Deposition across and around Triassic Pangaea took place mostly in foreland, fore-arc and extensional basins, and the Triassic was a time of relatively low levels of volcanism. -
227 BCE
In the Triassic period the dinosaurs began to appear.
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Period: 201 BCE to 145 BCE
Jurassic Period
Jurassic Period, second of three periods of the Mesozoic Era. Extending from 201.3 million to 145 million years ago, it immediately followed the Triassic Period (251.9 million to 201.3 million years ago) and was succeeded by the Cretaceous Period -
172 BCE
During the Jurassic period, the supercontinent Pangaea split apart. The northern half, known as Laurentia, was splitting into landmasses that would eventually form North America and Eurasia, opening basins for the central Atlantic and the Gulf of Mexico.
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Period: 145 BCE to 66 BCE
Cretaceous Period
Cretaceous Period, in geologic time, the last of the three periods of the Mesozoic Era. The Cretaceous is the longest period of the Phanerozoic Eon. Spanning 79 million years, it represents more time than has elapsed since the extinction of the dinosaurs, which occurred at the end of the period. -
85 BCE
During the Cretaceous, accelerated plate collision caused mountains to build along the western margin of North America.
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Period: 66 BCE to 50
Cenozoic Era
Cenozoic Era, third of the major eras of Earth's history, beginning about 66 million years ago and extending to the present. It was the interval of time during which the continents assumed their modern configuration and geographic positions and during which Earth's flora and fauna evolved toward those of the present. -
65 BCE
The Tertiary Period began when a meteorite called Chicxculub slammed Earth, extinguishing the 75% of the all species on our planet.
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Period: 65 BCE to 1 BCE
Tertiary Period
This period began 65 million years ago and ended roughly 1.8 million years ago and bore witness to some major geological, biological and climatological events. This included the current configuration of the continents, the cooling of global temperatures, and the rise of mammals as the planet's dominant vertebrates. -
Period: 1 BCE to 50
Quaternary Period
The Quaternary Period is the second period of the Cenozoic Era. You and I are living in this period, which began only 1.8 million years ago. This is less than 0.1% of all of geologic time! A thin layer of sediments deposited during the Quaternary covers much of the Earth's land surface. -
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The Quaternary Period is famous for the many cycles of glacial growth and retreat, the extinction of many species of large mammals and birds, and the spread of humans.
