Proterozoic
Overview
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth
. The name Proterozoic comes from the Greek "earlier life". The Proterozoic Eon extended from to (million years ago), and is the most recent part of the old, informally named ‘Precambrian
’ time.
The Proterozoic consists of 3 geologic eras, from oldest to youngest:
The well-identified events were:
The geologic record of the Proterozoic is much better than that for the preceding Archean
.
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. The name Proterozoic comes from the Greek "earlier life". The Proterozoic Eon extended from to (million years ago), and is the most recent part of the old, informally named ‘Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
’ time.
The Proterozoic consists of 3 geologic eras, from oldest to youngest:
- PaleoproterozoicPaleoproterozoicThe Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
- MesoproterozoicMesoproterozoicThe Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them...
- NeoproterozoicNeoproterozoicThe Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
The well-identified events were:
- The transition to an oxygenOxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
ated atmosphereAtmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
during the MesoproterozoicMesoproterozoicThe Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them...
. - Several glaciationsGlacierA glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
, including the hypothesized Snowball EarthSnowball EarthThe Snowball Earth hypothesis posits that the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 Ma . Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical...
during the CryogenianCryogenianThe Cryogenian is a geologic period that lasted from . It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran...
period in the late NeoproterozoicNeoproterozoicThe Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
. - The EdiacaranEdiacaranThe Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
Period (635 to 542 Ma) which is characterized by the evolution of abundant soft-bodied multicellular organisms.
The geologic record of the Proterozoic is much better than that for the preceding Archean
Archean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...
.
