Precambrian
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World Map
This map is of the landmass positions near the end of the Precambrian.
The movement of Earth's plates has caused the formation and break-up of continents over time. The earliest known supercontinent was Vaalbara, which formed around 3.636 billion years ago and broke up around 2.845-2.803 billion years ago. Later, the supercontinent Kenorland formed around 2.72 billion years ago and broke up into smaller proto-continent cratons around 2.45-2.1 billion years ago. The supercontinent Columbia (or Nuna) formed around 2.1-1.8 billion years ago and broke up around 1.3-1.2 billion years ago. The supercontinent Rodinia is thought to have formed around 1300-900 million years ago and broke up into eight continents around 750-600 million years ago.
Climate
The Precambrian era, spanning approximately 4.6 billion years, accounts for nearly 90% of Earth's history. During this vast period, the climate underwent significant transformations, with radical changes occurring over the course of 4 billion years. The early days of Earth's life, known as the Hadean eon, were marked by intense volcanic activity and a hostile environment that was inhospitable to life. The Hadean era, named after Hades, the Greek god of the underworld, lasted around 500 million years.
The Archaean eon, which followed, was characterized by a lack of oxygen in the atmosphere. Despite this, simple unicellular life is believed to have emerged during this time, initiating photosynthesis. This crucial event led to the Great Oxygenation Event, which had a profound impact on the planet's ecosystem and nearly wiped out all life. As the Proterozoic eon unfolded, the climate became more stable, with a warm and relatively consistent temperature range. This stability allowed for a reduced need for significant evolutionary adaptations in organisms, enabling them to thrive in their environments.
Flora
The fossil record suggests that terrestrial plant life did not emerge until the Ordovician period, approximately 470 million years ago. However, it's likely that simple plant forms existed earlier, potentially even during the Cambrian period or earlier in the Precambrian era. Unfortunately, these early plants were likely soft-bodied and lacked the hard structures that would have allowed them to fossilize well, leaving behind no tangible evidence of their existence.
Fauna
The emergence of advanced single-celled eukaryotes occurred after the Great Oxidation Event, which may have been caused by an increase in oxidized nitrates that eukaryotes use. This event marked a significant turning point in the evolution of life on Earth. During the Proterozoic era, symbiotic relationships between mitochondria and chloroplasts and their hosts evolved, allowing for the development of more complex cellular structures.
By the late Palaeoproterozoic era, eukaryotic organisms had become moderately diverse, with many different species emerging. However, cyanobacteria continued to thrive and even reached their peak diversity around 1200 million years ago. This suggests that eukaryotes and prokaryotes coexisted and competed for resources during this period.
The earliest fossils of fungi date back to the Paleoproterozoic Era, around 2,400 million years ago. These early fungi were multicellular and had filamentous structures capable of anastomosis, allowing them to connect with other fungi and form larger networks.
Traditionally, the boundary between the Proterozoic and Phanerozoic eons was set at the base of the Cambrian Period, when the first animal fossils appeared. However, discoveries in recent decades have shown that multicellular life had already become widespread tens of millions of years before the Cambrian Explosion. This has led to a reevaluation of the timing of this event, with some scientists proposing that the Proterozoic era should be extended to include this period of rapid evolution.
Etymology
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Stratigraphy
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Sources
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