Starts: 542 m.y.a.
Ends: 488 m.y.a
In the early Cambrian, Earth was generally cold but was gradually warming as the glaciers of the late Proterozoic Eon receded. Tectonic evidence suggests that the single supercontinent Rodinia broke apart and by the early to mid-Cambrian there were two continents. Gondwana, near the South Pole, was a supercontinent that later formed much of the land area of modern Africa, Australia, South America, Antarctica and parts of Asia. Laurentia, nearer the equator, was composed of landmasses that currently make up much of North America and part of Europe. Increased coastal area and flooding due to glacial retreat created more shallow sea environments.
Plate Tectonic Formation
There is still some controversy about whether any true plants existed as far back as the Cambrian period. If they did, they consisted of microscopic algae and lichens (which don’t tend to fossilize well). It’s a surer bet that macroscopic plants like seaweeds had yet to evolve during the Cambrian, given their noticeable absence in the fossil record.
The Cambrian Period (542 to 488 million years ago) was the time when most of the major groups of animals first appeared in the fossil record.
This event is sometimes called the “Cambrian explosion,” because of the relatively short time over which this diversity of forms appeared.
Citation: Earth Viewer App
The scale of the Cambrian Explosion is likely exaggerated due to the proliferation of hard-bodied animals that fossilized much more readily than their soft-bodied precursors. These included brachiopods, which lived in shells resembling those of clams or cockles, and animals with jointed, external skeletons known as arthropods—the ancestors of insects, spiders, and crustaceans. These toughened-up creatures represented a crucial innovation: hard bodies offering animals both a defense against enemies and a framework for supporting bigger body sizes.
Atmosphere (temp & gasses)
The climate at the beginning of this period was cold, but over time the climate in all parts of the Earth grew warmer. This made the seas a good place for many species to live. The continents were still forming. They were mostly barren rocks. The land had no plant or animal life on it yet.
Atmosphere: O2 31.4%, CO2 0.12%
Not a lot is known about the global climate during the Cambrian period, but the unusually high atmospheric carbon dioxide levels (about 15 times those of the present day) imply that the average temperature may have exceeded 120 degrees Fahrenheit.
Oceans (temp & chemistry)
Most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia. The seas were relatively warm, and polar ice was absent for much of the period.
Eighty-five percent of the earth was covered with water (compared to 70 percent today), most of that area being taken up by the huge Panthalassic and Iapetus oceans; the average temperature of these vast seas may have been in the range of 100 to 110 degrees.