Earth formed about 4.54 billion years ago, roughly one-third the age of the universe, through a process called accretion within the solar nebula—a vast, rotating cloud of gas and dust left over from the formation of the Sun[2][5]. This solar nebula was composed mainly of hydrogen and helium, along with heavier elements produced by earlier generations of stars. Around 4.5 billion years ago, possibly triggered by a shock wave from a nearby supernova, the nebula began to collapse under its own gravity. As it contracted, it flattened into a spinning disk called the protoplanetary disk, with the Sun forming at the center and dust and particles orbiting around it[2].
Within this disk, tiny dust grains collided and stuck together, gradually building larger and larger clumps known as planetesimals—rocky bodies tens to hundreds of kilometers across. Through countless collisions and gravitational attraction, these planetesimals merged into protoplanets, including the early Earth[2][4]. This process, called runaway accretion, allowed Earth to grow rapidly, reaching near its current size within 10 to 20 million years, although recent studies suggest it may have formed even faster, in just a few million years[2].
During this early stage, Earth was a molten, inhospitable world due to the intense heat from frequent collisions, radioactive decay, and gravitational compression[3][5]. The heaviest elements, like iron and nickel, sank toward the center, forming Earth’s metallic core, while lighter materials rose to create the mantle and crust. This differentiation was crucial, as the iron core generates Earth’s magnetic field through convection currents, protecting the planet from harmful solar radiation[3].
One of the most dramatic events in Earth’s formation was a colossal collision with a Mars-sized body often called Theia[2][3][4]. This giant impact, occurring during the late Hadean eon, blasted a huge amount of debris into orbit around Earth. This debris eventually coalesced to form the Moon. The impact also vaporized much of Earth’s early atmosphere and melted large parts of the planet’s surface, but over time, Earth cooled and stabilized[3][4].
Volcanic outgassing from the cooling Earth released gases that formed the primordial atmosphere, initially lacking oxygen. Water vapor condensed to create the early oceans, possibly supplemented by water delivered from comets and asteroids during the late heavy bombardment period[2][3][5]. Over hundreds of millions of years, Earth’s surface continued to evolve, with continents forming and breaking apart, setting the stage for the emergence of life.
Summary of Earth’s Formation:
– Earth formed about 4.54 billion years ago by accretion of dust and rock in the solar nebula surrounding the young Sun.
– Dust particles collided and stuck together, forming planetesimals and then protoplanets through runaway accretion.
– Intense heat melted Earth, causing heavy elements to sink and form the core, while lighter materials formed the mantle and crust.
– A giant impact with a Mars-sized body (Theia) created the Moon and reshaped Earth’s surface and atmosphere.
– Volcanic outgassing and comet impacts formed Earth’s early atmosphere and oceans.
– Over billions of years, geological and biological processes transformed Earth into the habitable planet we know today.
References:
[2] History of Earth – Wikipedia
[3] Earth Timeline: A Guide to Earth’s Geological History and Events
[4] How the Earth and moon formed, explained – UChicago News
[5] Geological history of Earth – Wikipedia
Read More
[1] https://dynamicearth.org.uk/geological-timeline-pack-2.pdf
[2] https://en.wikipedia.org/wiki/History_of_Earth
[3] https://earthhow.com/earth-timeline-geological-history-events/
[4] https://news.uchicago.edu/explainer/formation-earth-and-moon-explained
[5] https://en.wikipedia.org/wiki/Geological_history_of_Earth
[6] https://www.livescience.com/46593-how-earth-formed-photo-timeline.html
[7] https://www.gsi.ie/en-ie/education/our-planet-earth/Pages/The-Earth-through-time.aspx
[8] https://www.newscientist.com/article/dn17453-timeline-the-evolution-of-life/