Hadean Eon: The Beginning of the Earth

Hadean Eon: Formation of the Earth
Hadean Eon is often regarded as the period when the Earth was formed. The International Commission on Stratigraphy does not recognize this to be a real Era although there have been much notable changes within.
Hadean Eon can be best understood through its division of 4 periods:

  • Cryptic
  • Basin Groups
  • Nectarian
  • Early Imbria

All these created were created based on the moons geology as there was no proof of survival of the Earth's surface. It was also known that the moon was devoted of water and wind. It also suffered from lower volcanic activities.

Hadean Eon: Cryptic Period
This is also known as the "Hidden" period. This Cryptic period is the earliest phase of the Earth recorded. The period is estimated to last from 4.56 to 4.50 billion years ago. It is named "cryptic" because the moon is also untouched by of any preserved details during this time. It is thought that the moon was formed at this cryptic period as well. The information and knowledge to describe this period are mainly based on the studies and calculations of meteorites and their physical models.
Highly presumed by scientists, about 4.56 billion years ago the solar nebula gave birth to the Earth. The gravitational force matter aggregated into clumps then started to grow in size which attracted more materials. There has been no accurate nor real knowledge to be found to measure the time of formation of the Earth but through computer models, the planet formation process was proven to be rapid and it may have took a couple of million years to complete the process entirely.
The meteorites of the oldest basaltic period support this theory that it took much less time to form the Earth and the solar system. High temperatures and great pressures were responsible for the formation of basalt and the reason the planetesimals existed at the cores at a very early stage.

As a result of this violation of formation, the earth was initially molten. Meteorite impacts, gravitational compression, radioactive decay of potassium, thorium, and uranium generated heat were all contributing factors. Iron and similar heavier elements began to sink towards the earth's center as temperature started to increase. It began to cross the irons' melting point, at roughly 1500 °C. This phenomenon is known as iron catastrophe and had partial contribution to the formation of iron-rich core of the Earth.
Gravitational potential energies were released due to the falling of heavier elements to the Earth’s core. This may have raised the Earth’s temperature to a high of 1000 C. It is also believed that the Earth suffered from a collision with a huge planetesimal, often known as Theia. It resembled the size of Mars. From this impact the Earth gained a good percent of its mass. The estimate was 10%. This finally gave birth to the moon. The process of the formation of moon was thought to take about 10-15 million years. Apart from this large collision of the Earth with the Theia there were other evidences of collision of other planets.
The Cyptic period ends with the completion of the Earth. However, it was presumed that after 60 to 80 million years of the formation the Earth reached its stage of completion with 99% of its present mass, moon, and the rich core of nickel and iron. Impacts of comets on the Earth and the out gassing of rock are responsible for the formation of water although in the form of vapor during this period.

Hadean Eon: Basins Groups,
This is relatively a long period covering 550 million years' timeframe and lasted about 4.50 to 3.80 billion years ago. There was lack of evidence of rocks of this period so lunar geology is the major source for extrapolating the Earths evolutional path during this time period. Still, despite the many major researches, the early history of the moon was still not very clear.
The rocks which were discovered from the lunar highlands were of the oldest to exist. It was thought by geologists that the lunar crusts were melted due to the higher frequency of the early impacts. It is estimated that about 4.4 to 4.2 billion years ago the features of the lunar crust were stabilized and differentiated from those of present day lunar crust. It can be said that this phase was the cryptic period of the moon and due to frequent impacts the surface of the moon. These impacts were not from not solid debris and at most times even frequently in a liquefied form. The period also left older rock specimens which were found scattered throughout the moon's surface. Erosion did not take place on the surface of the moon and as a result many of the rocks did survive to modern day.

The Earth suffered from a higher frequency of the impacts. The zircons and other oldest rocks found on the Earth were known to belong to this period. It was also thought that there was proto crust at the Earth and the crust was basaltic in nature.
Summed up, it can be said that the Earth continued to cool at the Basin period and the liquid water first appeared probably 4.4 billion years ago paving way to life.

Hadean Eon: The Nectarian Era
Lasted from 3.95 billion - 3.85 billion years ago the Nectarian era is a small part of the Hadean Eon. The phase called Late Heavy Bombardment started at this period and continued to the Imbrian.

Hadean Eon: The Imbrian period
Thought to have lasted from 3.85 billion - 3.80 billion years ago, this Imbrian period is the concluding part of the Hedean Eon. There are two distinct phases of this period and each characterized by their respective features. 2 large craters, the Orientale, and Imbrium marked the Early Imbrian.