This is the first and by far the longest geological period in Earth's history. It encompasses the time since the creation of the planet itself up to the start of the Cambrian period about 570 millions years ago; this makes the Precambrian approximately 4.5 billion years long! With recent discoveries in geology - in particular the discovery of very early life forms within Precambrian rocks - the term is now falling out of academic usage, although is still used as a general term. One of the features of the Precambrian was the lack of any evidence for life in rocks from that are; this is now known not to be the case.
All geologic time, and its corresponding rocks, before the beginning of the Paleozoic; it is equivalent to about 90% of geologic time. Precambrian time has been divided according to several different systems, all of which use the presence or absence of evidence of life as a criterion.
The first of the four Geologic Eras in which geologic time is divided. It extends from the beginning of Earth history (over 4 billion years ago) to the beginning of the Paleozoic Era (about 570 million years ago).
The division of geologic time from the formation of Earth (about 4.5 billion years ago) to the beginning of the Cambrian Period of the Paleozoic Era (about 600 million years ago). Also, the rocks formed during that time. Precambrian time constitutes about 90% of Earth's history.
adjective describing time before the Cambrian Era which was the time in Earth history when the first macroscopic life was found in the fossil record (in England when historical geology was first developing). The Precambrian-Cambrian boundary has recently been shifted in absolute time by Sam Bowring, John Grotzinger, and Beverly Saylor at MIT. It is now placed at about 540 million years ago. Thus, Precambrian time covers all rocks older than 540 million years old, including Hadean, Archean, and Proterozoic time.
All rocks formed, deposited and/or altered before the deposition of the Paleozoic rocks. Geologists assign a timeframe of 4500 million years to 570 Mya to these rocks. The Archean eon supposedly lasted from 4500 m.y. to 2500 m.y. with the Proterozoic eon comprising the remaining Precambrian time, 2500 m.y. to 570 m.y.b.p.
All geologic time before the beginning of the Paleozoic era. This includes about 90% of all geologic time and spans the time from the beginning of the earth, about 4.5 billion years ago, to 544 million years ago. Its name means "before Cambrian."
Informal term describing 7/8 of geologic time from the beginning of the earth to the beginning of the Cambrian Period of the Paleozoic Era. During this time the atmosphere and oceans formed, life originated (or possibly "colonized" Earth), eukaryotes and simple animals evolved and by the end of the precambrian they began to accumulate hard preservable parts, the common occurrence of which marks the beginning of the Cambrian. PICTURE
The time-frame of the Precambrian period is 4.5 billion years to approximately 545 million years ago (when the Cambrian period begins). The Precambrian is divided into 3 eras, characterized as follows: Hadean (4.5 – 3.9 billion years ago): From the formation of the Earth until the first appearance of sedimentary rocks, with no record of fossil organisms. Archaen (3.9 – 2.5 billion years ago): Appearance of sedimentary rocks, stromatalites, and benthic prokaryotes. Proterozoic (2.5 -0.545 billion years ago): Appearance of planktonic prokaryotes, followed by appearance of eukaryotic cells, followed by appearance of multicellular organisms.
The earliest part of the geological time scale, including all corresponding rocks, equivalent to about 90 percent of geologic time; from the beginning of time until the beginning of the Paleozoic, about 600 million years ago.
The ancient epoch of geological time (3.5 billion to 600 million years ago), marked in the North Country by the Early Precambrian Keewatin, Laurentian, Knife Lake, and Algoman periods (3.5 to 2.7 billion years ago); the Middle Precambrian Early, Middle, and Late Huronian( Animikean) periods (2.6 to 1.6 billion years ago); and the Late Precambrian Early, Middle, and Late Keweenawan periods (1.6 billion to 600 million years ago).
The Precambrian (or Pre-Cambrian) is an informal name for the eons of the geologic timescale that came before the current Phanerozoic eon. It spans from the formation of Earth around 4500 Ma (million years ago) to the evolution of abundant macroscopic hard-shelled fossils, which marked the beginning of the Cambrian, the first period of the first era of the Phanerozoic eon, some 542 Ma.