Proterozoic eon

Proterozoic Eon

The Proterozoic Eon is a geological eon representing a period in Earth's history that extends from 2.5 billion years ago (Ga) to 541 million years ago (Ma), just before the Cambrian explosion in the Phanerozoic Eon. It is the most recent part of the Precambrian time and is further subdivided into the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic eras.

Overview

The Proterozoic Eon followed the Archean Eon and was a period of significant changes in the Earth's atmosphere, climate, and life forms. It is characterized by the accumulation of oxygen in the Earth's atmosphere due to the photosynthesis of cyanobacteria, leading to the Great Oxygenation Event. This event caused a significant extinction of anaerobic organisms and paved the way for the development of more complex life forms.

Subdivisions

The Proterozoic Eon is divided into three geological eras:

• Paleoproterozoic Era (2.5 - 1.6 Ga): This era is marked by the first continents, the appearance of stable crust, and the first evidence of plate tectonics.
• Mesoproterozoic Era (1.6 - 1.0 Ga): This era is characterized by the formation of supercontinent Rodinia and the evolution of sexually reproducing organisms.
• Neoproterozoic Era (1.0 Ga - 541 Ma): This era is known for the breakup of Rodinia, the Snowball Earth hypothesis, and the first multicellular life forms.

Life in the Proterozoic Eon

The Proterozoic Eon saw the evolution of the first complex life forms. The oxygenation of the atmosphere allowed for the development of aerobic organisms and eventually multicellular life. The first multicellular organisms, such as Ediacaran biota, appeared towards the end of the Proterozoic, setting the stage for the Cambrian explosion of life in the following Phanerozoic Eon.

See also

• Geological time scale
• History of Earth
• Precambrian