The Precambrian Era

The Precambrian Era refers to the geological time scale that existed before the current Phanerozoic eon, an age prior to 550 million years ago. An eon is a specific measure of lapsed time, to enable a more comprehensive study of the Earth's dynamics, since its formation around 4500 million years ago. The Precambrian eon roughly accounts for around seven-eighths of the Earth's history. The fossil remains unearthed, offer an insight into the existence of stromatolites. Most of the Precambrian rocks are either metamorphosed heavily or destroyed by the forces of erosion. This soil and rock feature makes most of the Precambrian fossils excavated of little biostratigraphic use, while many more remain deeply embedded within the Phanerozoic strata.

The term Precambrian is commonly used by geologists and paleontologists to refer the time zone prior to the Cambrian eon. This era is studied extensively to find a connection with the fossil remains of bacterial life, that date back to nearly 3460 million years ago. The era is believed to be characterized by the presence of bacterial life forms and those of multi-celled crustaceans. The Precambrian Era developments are more suppositions than proven facts. The time span is characterized by tectonic plate motions, formation of proto-continents, glacial periods, the Huronian epoch and an atmosphere smothered in decreasing gas content and free oxygen. It is believed that the Earth, during the Precambrian Era, had a reddish tint, and flaunted olive green oceans and seas. The oceans were hosts to insoluble substances and evolving life forms.

This era, towards the end, witnessed a resurgence of atmospheric oxygen, due to developing photosynthesis, and the ecological crisis also referred to as the 'oxygen catastrophe'. At that time, atmospheric oxygen was an essential part of chemical reactions, till such time that surfaces that could be oxidized were completely exhausted. It is only after the oxygen catastrophe, that the planet witnessed the development of a high-oxygen atmosphere. Precambrian fossils are mostly contained in such banded iron rock formations, apparently the result of the iron-oxygen combination. The Precambrian Era also witnessed the collision of crustal blocks and the formation of mountain chains. Most life forms that existed during the era were forms of bacteria and algae. Blue-green stromatolites, multi-celled metazoans and the Ediacaran fauna thrived despite the extremely challenging conditions. There are traces of the Cnidaria oder and unknown grazing animals also discovered in unearthed Precambrian fossils. In fact, geologists agree that the Precambrian time zone envelopes a huge chunk of the Earth's history and is easily the earliest of all geologic ages, marked in layers of sedimentary rock and fossilized remains.

Scientists believe that the Earth was more than 600 million years old when the earliest traces of life appeared on the surface. This Precambrian time scale witnessed a lot of atmospheric activity and early evolution. It is synonymous of the cooling down of molten surface of the planet, and subsequent development of a solid crust, formation of oceans, life in the primordial seas, catalytic mineral-rich volcanic vents, and the birth of the first cell membranes. The Precambrian fauna comprised sponges and annelids that faced widespread extinction, due to the subsequent prolonged global ice age. The Precambrian Era witnessed the formation of the Earth's geosphere, atmosphere and hydrosphere and a sort of quantum leap in the evolution of the first microbes.