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Paleozoic Era
atmospheric oxygen reached its modern day levels, producing the ozone shield that screens out ultraviolet radiation and allows complex life to live in the shallow waters and finally on land. This era witnessed the age of invertebrates, of fish, of tetrapods, and reptiles. From the Silurian on, life emerged from the sea to colonize the land, and in the later Paleozoic plants flourished. Towards the end of the Paleozoic, the continents clustered into the supercontinent of Pangea. -
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Proterozoic Era
the atmosphere change to oxygenated, driving the original anaerobic inhabitants of the Earth into near extinction. The modern regime of continental drift began, and saw the formation of supercontinent of Rodinia, and several extensive ice ages. Late in the Proterozoic a runaway icehouse effect meant that the earlier warm conditions were replaced by a "Snowball Earth" with ice several kilometers deep covering the globe. Warming conditions saw the appearance of the first metazoa. -
Meszoic Era
Lasting little more than half the duration of the Paleozoic, this was a spectacular time. The reptiles of the Triassic gave way to the dinosaurs, a terrestrial megafauna the like of which the Earth has not seen before or since. While dinosaurs dominated the land, diverse sea-reptiles ruled the oceans, and invertebrates, especially ammonites, were extremely diverse. At the end of the Cretaceous period the dinosaurs and many other animals abruptly died out, -
Cenozoic Era
With the extinction of the dinosaurs and the end of the Mesozoic, the mammals swiftly inherit the Earth. The appearance of grass meant the rise of grazing mammals, and the cooler drier world allowed modern mammalian groups to evolve, along with other lineages now extinct and a few archaic hold-overs. This era saw the rise of Man. -
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Archean Era
the Archean was a time when diverse microbial life flourished in the primordial oceans, and the continental shields developed from volcanic activity. to develop, and plate tectonics followed a regime of continental drift different to that of the Proterozoic and later. -
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Hadean Era
the formation of the Solar System and Earth, and the outgassing of the first atmosphere and oceans. A hellish (Hades) period lasting some 760 million years, when the Earth was subject to frequent bombardment by comets, asteroids, and other planetary debris. This was an era characterized by extensive volcanism and formation of first continents. By the end of the Hadean, the Earth had an atmosphere.
