The early earth

How Was the earth formed?

In this section, we will learn how solar nebula began to collapse under its own gravity, it began to spin faster and flatten into a disk shape forming Sun. This spinning disk of material began to clump together to form larger bodies, such as planetesimals. We will learn how these planetesimals continued to collide and merge, they eventually formed the larger bodies in the solar system such as the planets, moons, and asteroids.

Section Preview: 3D model of Solar System

8-10 billion years ago
The Milky Way

Our galaxy, the Milky Way, was formed by the merger of several other galaxies.

The formation of the Milky Way galaxy is thought to have occurred through a process called hierarchical structure formation. This process involves the gradual accumulation of smaller structures, such as gas clouds and smaller galaxies, into larger structures, such as the Milky Way.

In the early universe, after the Big Bang, the universe was filled with dark matter, gas, and small fluctuations in density. These density fluctuations eventually led to the collapse of some regions, forming the first generation of stars, called population III stars, which are thought to be massive and short-lived.

As these first stars died and exploded, they released heavy elements, which then cooled and collapsed to form the next generation of stars, called population II stars. These stars formed in small, dense clumps called globular clusters.

Over time, these globular clusters and other small structures began to merge and accrete to form larger structures, such as dwarf galaxies. Eventually, these dwarf galaxies collided and merged to form our current galaxy, the Milky Way.

4.57 billion years ago
The Solar System

The solar system is thought to have formed about 4.6 billion years ago from a large, rotating cloud of gas and dust called the solar nebula. The solar nebula was likely formed from the remnants of previous generations of stars and their supernovae explosions.

Astronomical data and hydrodynamic models of star formation support the idea that stars, including the sun, formed by the gravitational collapse of a molecular cloud core made of material manufactured and reprocessed in many previous generations of stars. The forming star is surrounded by a rotating disk of gas and dust because the typical molecular cloud rotates at the time of collapse. When observed through a telescope, the majority of the disc surrounding the young stars is made up of 99 percent gas and 1 percent dust.

The Gaseous Planet
According to Core Accretion Model, The development of the Giant planet began with the condensation and coalescence of rocky and ice material to produce masses several times the size of Earth. These solid bodies then attracted and accumulated gases from the circumstellar disk. Disk Instability Model suggests, that the development of gas giant planets does not require the presence of a rock or an ice ball; they can originate directly from the gas and dust in the disk, which can collapse under its own gravity like a miniature sun. This is how giant gas planets like Jupiter and Saturn were formed. Solar wind clears out much of the gas disk, ending growth by gas accretion.
4.567 billion year ago
Formation of Earth

As the Solar Nebula began to cool, the remaining dust grains started to bind together. The further development of a Terrestrial planet is thought to have occurred in phases, beginning with the production of a small planetesimal about 10 km in diameter. Many of the early plants were destroyed as they collided.

Planetesimals that were not destroyed expanded quickly to the size of a moon (>1000km diameter). This rapid accretion quickly began to reduce material in the vicinity surrounding the planetesimals from which it was growing.

These planetesimals created a few planetary embryos that were around the size of Mars (>5000 km diameter). Only a few planetary embryos were growing and they all grew to be around the same size. Accumulation slowed as planetary materials were accreted from the surrounding.

4.5 billion years ago
Migration of Jupiter
Jupiter migrated inward, preventing planet formation in the asteroid belt and limiting Mars' material supply. After that, it entered a resonance with Saturn and moved to its current orbit.
Planetary Differentiation of Earth

Iron, the most abundant element capable of forming a dense molten metal phase, gathered in planetary core. Siderophile ("iron-loving") elements descend into the core because they dissolve easily in iron, either as solid solutions or in molten form.

Lithophile elements ("rock-loving")  remained on or near the Earth's surface because they readily react with oxygen to create compounds that do not sink into the Earth's core.

At temperatures and pressures found on the surface, atmophile elements (also known as "volatile elements") remain predominantly on or above the surface because they occur as liquids and/or gases.

Primordial Crust

The terrestrial planets most likely had magma oceans on their surfaces at the ending of planetary accretion. These formed  crust when they cooled. Because of their strong attraction for oxygen, lithophile elements formed very strong associations with silica, resulting in relatively low-density minerals that float to the Earth's crust. This crust was most likely destroyed by major impacts and reformed numerous times until the Heavy Bombardment Era came to an end. None of the Earth's primordial crust has survived to the present day.

4.45 billion years ago
The Moon

Terrestrial planets had largely formed by continual accretion of rocky protoplanets. According to Giant Impact hypothesis, around 4.5 billion years ago, a Mars-sized body named Theia collided with the early Earth, causing a massive amount of debris to be blasted into orbit around the Earth. This debris eventually came together to form the Moon.

The collision would have been so violent that it would have vaporized a large portion of both Theia and the Earth, and the ejected material would have formed a ring around Earth. This ring would have cooled and solidified to form the Moon.

4 billion years ago:
The Oceans

The formation of the first oceans on Earth is thought to have occurred through a process called outgassing. This process involves the release of water vapor and other volatile compounds from the interior of the planet, through volcanic activity.

The early Earth was a very hot and dry place, with temperatures high enough to boil away any water that may have existed. However, as the planet cooled and solidified, water vapor was able to condense and collect in the form of oceans.

The water vapor was likely released from the Earth's interior through volcanic activity, which also released other gases such as carbon dioxide and methane. These gases may have formed a primitive atmosphere that helped to trap heat and keep the planet warm enough for liquid water to exist.

Torrential downpours lasting millions of years formed the Earth's oceans, allowing new chemicals to be formed in a liquid environment. Subsequently giving a platform for origin of Life. 


Chemical Cook up


Emergence of Life