The Cambrian Period

The Cambrian period began 542 million years ago, and lasted for 54 million years; till the beginning of Ordovician period. The Cambrian period is marked as a Milestone in Earth’s history because of the profound change of life that took place during the period. Larger, more complex multicellular organisms became more prominent beneath the ocean; i.e. mollusks, arthropods, etc.image

542 million years ago, the Earth was extremely barren on land. While a variety of macroscopic marine plants existed below the surface, and while some microbes and fungi formed microbial ecosystems inland, there was little life beyond the ocean. However, under the ocean is a different story. In the early Cambrian period, a steep change in biodiversity occurred. Varying sub-species of arthropods were prominent; most common was the Trilobite. However, later in the period the number of varying genera decreased. Meanwhile, the atmosphere of Earth was known to be very cold, with very little oxygen in the air. This is because of the absence of bacteria that make breathable air. The oceans were shallow, but warm. The lack of oxygen didn’t affect the creatures beneath the ocean though.


Cambrian Time Period

Starts: 542 m.y.a.
Ends: 488 m.y.a

Geologic Information:
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
Plate Tectonic Formation

Flora (plants)
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.

Fauna (animals)
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.


ABSOLUTE DATE : 540- 490 million years ago

GEOLOGY: The break up of the supercontinent Pannonia happened durning the Cambrian period. The continents were dry and rocky. The land was pretty barren durning the Cambrian period. Land had no animal or plant life yet.

FLORA( plants) : During the Cambrian period there were a variety of marcoscopic plant life in the oceans. One of the plants found in the oceans durning the Cambrian period was the margaretia.

FAUNA (animals): The Cambrian period marked a profound change in life on earth. Prior to the Cambrian period living organisms were unicellular and simple. Complex, multicellular organisms appeared more commonly I. The millions of years after the Cambrian period. The Cambrian period is sometimes called the ” Cambrian explosion” because of the relatively short time over which this diversity of forms appeared. Durning this period major groups of animas first started to appear in fossil records . It was not until the Cambrian period that mineralized organisms became common. The first representatives of many modern species are found in the Cambrian period.

ATMOSPHERE : Durning the Cambrian period there was plentiful atmospheric oxygen.

OCEANS : Durning the Cambrian period diverse life forms were found in the oceans,  seas were warm, polar ice was absent for much of the Cambrian period. All living organisms were found in the oceans durning the period. Since the land have no plants or animals yet. The oceans contained all life forms. Some of the life forms found in the oceans durning the Cambrian period would have been mollusks and Arthropods.









Trilobite fossil mold



Photo by R. Weller/ Cochise college,


The first appearance of trilobites was in the Cambrian period and found up to the upper permian period. After that, the trilobites went extinct in the catastrophe that removed over 90% of all the species on earth. It was called the Permian extinction and it marked the end of the Paleozoic and the start of the mesozoic