Today we're going to travel back to the beginnings that mark geological time , to the first eon that marks the history of our planet: the Precambrian. This is a rather old term, but widely used to describe the period of Earth's existence before rocks formed. We're going to journey to the very beginning of Earth, close to a period of its formation. Fossils have been discovered that reveal some Precambrian rocks. This period is also known as the "dark life."
If you want to know everything related to this era of our planet, in this post we will tell you everything. You just have to keep reading
Beginnings of the planet
Formation of the solar system
The Precambrian covers almost 90% of Earth's history. To better understand it, it has been divided into three eras: the Azoic, Archean, and Proterozoic . The Precambrian eon encompasses all geological time prior to 600 million years ago. This eon has been defined as preceding the Cambrian Period. Today, however, it is known that life on Earth began at the start of the Archean and that fossilized organisms became more abundant.
The two subdivisions of the Precambrian are the Archean and the Proterozoic. The former is the oldest. Rocks less than 600 million years old are considered part of the Phanerozoic, which is crucial for understanding the evolution of our planet.
The duration of this eon begins from the formation of our planet about 4.600 billion years ago until geological diversification. It is when the first multicellular lives known as the Cambrian Explosion appeared that the Cambrian begins. This is dated about 542 million years ago.
There are some scientists who consider the existence of a fourth era within the Precambrian called Chaotian and that it is previous to all the others. It corresponds to the time of the first formation of our solar system.
Azoic
This first era took place between 4.600 billion and 4.000 billion years after the formation of our planet. At that time, the solar system was forming within a cloud of dust and gas known as the solar nebula. This nebula gave rise to asteroids, comets, moons, and planets.
It is theorized that if Earth collided with a Mars-sized planetoid called Theia, this collision may have added 10% of Earth's surface. The debris from this collision coalesced to form the Moon.
There are very few rocks from the Azoic era. Only a few mineral fragments remain that have been found in sandstone substrates in Australia. However, numerous studies have been conducted on the formations of the moon. They all conclude that the Earth was bombarded by frequent asteroid collisions throughout the entire Azoic era.
In this era the entire surface of the Earth was devastating. The oceans were liquid rock, boiling sulfur, and impact craters everywhere. The volcanoes were active in all areas of the planet. There was also a shower of rocks and asteroids that never ended. The air was hot, thick, full of dust and dirt. Back then there couldn't be life as we know it today, since the air was made up of carbon dioxide and water vapor. It had some traces of nitrogen and sulfur compounds.
Archaic
The name means ancient or primitive. It is an era that begins around 4.000 billion years ago. Things have changed from their previous era. Most of the water vapor that was in the air cooled and formed the global ocean. Most of the carbon dioxide was also turned into limestone and deposited on the ocean floor.
In this age the air was made up of nitrogen and the sky was full of normal clouds and rain. The lava began to cool to form the ocean floor. Many active volcanoes still indicate that the Earth's core is still hot. The volcanoes were forming small islands that, at that time, were the only land area there was.
Small islands collided with each other to form larger ones, and these, in turn, collided to form the continents, which are fundamental to Earth's geology today.
As for life, only single-celled algae existed at the bottom of the oceans . Earth's mass was sufficient to support a reducing atmosphere composed of methane, ammonia, and other gases. It was then that methanogenic organisms appeared. Water from comets and hydrated minerals condensed in the atmosphere. A series of torrential rains of apocalyptic proportions followed, forming the first oceans of liquid water.
The first Precambrian continents were different from what we know today: they were smaller and had surfaces of igneous rocks. No life lived on them. Because of the continuing force of the Earth's crust to shrink and cool, the forces accumulated below and pushed the land masses upward. This caused the formation of high mountains and plateaus that were built above the oceans.
Proterozoic
We are entering the last era of the Precambrian. It is also called the Cryptozoic, which means hidden life . It began about 2.500 billion years ago. Enough rock formed in the shields to initiate recognizable geological processes. This gave rise to the current plate tectonics, which is vital for understanding the dynamics of our planet.
By this time, there were prokaryotic organisms and some symbiotic relationships between living organisms. With the passage of time, the symbiotic relationships were permanent and that continuous conversion of energy went on to build chloroplasts and mitochondria. They were the first eukaryotic cells.
Around 1.200 billion years ago, plate tectonics forced shield rock to collide, forming Rodinia (a Russian term meaning “motherland”) , Earth’s first supercontinent. The coastal waters of this supercontinent were surrounded by photosynthetic algae. The process of photosynthesis added oxygen to the atmosphere. This caused the methanogenic organisms to disappear.
After a brief Ice Age, organisms underwent rapid differentiation. Many of these organisms were cnidarians, similar to jellyfish. Once the soft organisms gave rise to more elaborate organisms, the Precambrian eon came to an end, giving way to the current Phanerozoic eon.
With this information you will be able to learn something more about the history of our planet.
