The Proterozoic Eon, spanning from approximately 2.5 billion years ago to 541 million years ago, is a critical period in Earth’s history characterized by the diversification of life, the evolution of complex ecosystems, and significant geological changes.
Cratons became more stable, setting the stage for the development of more complex geological features.
One of the notable events of the Proterozoic was the assembly of the supercontinent Rodinia around 1.1 billion years ago. Rodinia’s formation influenced global tectonics, climate, and the distribution of land and sea.
Glaciations and “Snowball Earth” Events
The Proterozoic is marked by several severe glaciations known as “Snowball Earth” events. During these times, a significant portion of Earth’s surface was covered by ice, impacting sea levels and global climates. There is evidence of some of these events in rocks in Death Valley, California, which was near the equator at the time.
Evolution of Eukaryotic Life
The Proterozoic witnessed the further evolution and diversification of eukaryotic life forms. The appearance of the first multicellular organisms and complex ecosystems contributed to the shaping of environments.
Towards the end of the Proterozoic, the first animals with hard shells, such as mollusks and brachiopods, appeared. This marked a significant step in the evolution of animal life.
This was the Ediacaran Biota emerged. These were some of the earliest larger complex multicellular organisms, representing diverse forms of life that provide insights into the evolution of body plans.
Formation of Oxygen-Rich Atmosphere
The oxygenation of Earth’s atmosphere continued during the Proterozoic, leading to the establishment of oxygen-rich conditions necessary for the evolution of complex life forms. Many of the earlier life forms were poisoned by the increasing oxygen-rich conditions and became extinct.
Red Beds and Iron Formations
The Proterozoic saw the deposition of red beds and iron formations, similar to those of earlier eras. These rock types provide clues about changing atmospheric and oceanic conditions. These red beds include the Hakatai Shale, a geological formation within the Grand Canyon, which is estimated to be around 740 to 730 Ma.