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The Precambrian is an informal unit of geologic time, [3] subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga ) to the beginning of the Cambrian Period, about 538.8 million years ago ( Ma ), when hard-shelled creatures first appeared in ...
This timeline of natural history summarizes significant geological and biological ... the Precambrian comprises some 85% of geological time from the formation of ...
Precambrian: End-Ediacaran extinction: 542 Ma: Anoxic event [43] Great Oxygenation Event: 2400 Ma: Rising oxygen levels in the atmosphere due to the development of photosynthesis as well as possible Snowball Earth event. (see: Huronian glaciation.)
The Precambrian includes approximately 90% of geologic time. It extends from 4.6 billion years ago to the beginning of the Cambrian Period (about 539 Ma).It includes the first three of the four eons of Earth's prehistory (the Hadean, Archean and Proterozoic) and precedes the Phanerozoic eon.
During the Paleozoic, western North America lay underneath a shallow sea, which deposited many kilometers of limestone and dolomite. [7]In the southern Rocky Mountains, near present-day Colorado and New Mexico, the Precambrian and Paleozoic rocks were disturbed by mountain building approximately 300 Ma, during the Pennsylvanian.
Detailed logarithmic timeline – Timeline of the universe, Earth, and mankind; Earth phase – Phases of the Earth as seen from the Moon; Evolutionary history of life; Future of Earth – Long-term extrapolated geological and biological changes of planet Earth; Geological history of Earth – The sequence of major geological events in Earth's past
The Precambrian dates from around 3850 to 542 million years ago. The Neoproterozoic is characterized by a large glaciation event, followed by the appearance of the first multicellular body plans before the Cambrian Explosion. Until the late 1950s, the Precambrian was not believed to have hosted multicellular organisms.
The Pre-Cambrian had been believed to be without life (azoic); however, fossils were found in deposits that were judged to belong to the Azoic age. Before the Hadean Eon was recognized, the Archean spanned Earth's early history from its formation about 4,540 million years ago until 2,500 million years ago.