Question

how our earth formed

Answer 1

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In a process known as runaway accretion, successively larger fragments of dust and debris clumped together to form planets. Earth formedin this manner about 4.54 billion years ago (with an uncertainty of 1%) and was largely completed within 10–20 million years.


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Answer 2

The earth wasn’t always a magnificent blue marble, with colorful trees rustling in the gusts, with impeccable white sand beaches onto which green waves and foam lapse and disperse into each other. With its vacillating oceans and laconic mountains suffused with green, white and brown, inciting equanimity in us.

Later, we erected grandiose domes and numinous cathedrals, glass armored skyscrapers soaring high into the stainless sky. We drove copious cars, omnibuses and trains, the reminders of our mechanical routines, towards nowhere. There is a surge of people, tumultuous, bustling on platforms and in the streets. Life.

Earth actually started out as a hot, lifeless, sturdy rock, constantly buffeted by comets and meteorites for half a billion years. With volcanoes intermittently vomiting molten lava and beings, if any, perishing under the sun’s scorching rays. Rewinding even further, it seems that the planet emanated from sputtered particles and gas that came together under the inescapable lure of gravity.

The Core Accretion Scenario

Around 4.6 billion years ago, the larval solar system was a hot soup of dust and gas whirling around haphazardly in space. This vagrant matter is believed to have been produced in a supernova. As this nebula contracted, the matter rotated faster, like an ice skater pulling his hands inward. The nascent solar system thus contracted and flattened into a disk.

The dense cloud, compressed due to gravity, grew immensely hot and heavy in the center. This became the Sun. The matter on the outskirts of this nebula was pushed outward into space due to the force of solar winds. This matter aggregated through gravity and coalesced into what are called proto-planets and potential moons. The third proto-planet from the Sun was Earth.

The proto-planets were not only too small, but also far too hot, to keep hold of the volatile gases that were abundant in the nebula: hydrogen and helium. This is why terrestrial planets (Mercury, Venus, Earth and Mars) are composed of metals or silicate mantles. The atmospheres of these planets are either extremely thin or absent altogether.

On the other hand, because the Jovianplanets (Jupiter, Saturn, Uranus, Neptune) were distant from the conflagration, they were cool enough to accumulate these gases. These planets are primarily made up of hydrogen, helium, methane and ammonia, and are commonly labeled gas giants.

The Early Earth

It is estimated that the early Earth housed very high temperatures due to the elevated pressure from gravitational compression. Add to that the impact of meteors and incessant radioactive decay. This era is named the Hadean Age. Hadean is Greek for “the underworld”.

The initial Earth was largely molten. Like oil and water, the denser metallic liquid sunk deep into the center, forming the mostly iron core, while the less dense silicate liquids settled on top of it to form a rocky silicate mantle.
(Photo Credit : Naeblys / Shutterstock)

The constant bombardment of meteors and comets led to the formation of volcanoes, which combined with the already intrusive igneous activities on Earth to form the crust of our planet. The gases exhaled by these volcanoes also contributed to the formation of our thin, yet protective, atmosphere.

The water vapor slowly condensed and its quantity was augmented by the presence of ice-cold comets. The vapors that accumulated in the atmosphere cooled down the Earth’s molten exterior. This led to the formation of oceans. The volcanoes also replenished the atmosphere with carbon dioxide and nitrogen.