FORMATION OF THE EARTH

FORMATION OF THE EARTH

-       By Suhail Ansari

-       Batch(2k17), Deptt. of Chemical Engg.

-       BIT Sindri, Dhanbad

For the six million years humans have been on Earth has allowed them to evolve, build tools, create civilizations, adapt to their environment, and become the humans we are today.

But have you ever wondered, how the planet Earth made? How did Earth come into existence?

Let’s start with the origin of everything.

BIG BANG

Billions of years ago, all matter of the universe was compressed into one tiny point until it finally exploded around 12-14 billion years ago. This explosion is what scientists call the Big Bang.

At the moment of the Big Bang, all of the energy in the universe – some of which would later become galaxies, stars, planets and human beings – was concentrated into a tiny point, smaller than the nucleus of an atom. And it’s not just matter that was born in the Big Bang. In the view of modern cosmologists, matter and space and time all began when that microscopic point suddenly expanded violently and exponentially. (and it could still be stretching).

HOW WAS THE EARTH FORMED?

The core accretion model

Around 4.6 billion years ago, the giant solar system was a cloud of dust and gas surrounded all around in space known as a solar nebula. Gravity collapsed the solar nebula and began to spin at warp speed due to which the material contracted and flattened into a disk result as an immensely hot and so dense. This is how our sun was born.

                      Fig: Solar Nebula

With the rise of the sun, the remaining material began to clump up. Small particles drew together, bound by the force of gravity, into larger particles. The solar wind swept away lighter elements, such as hydrogen and helium, from the closer regions, leaving only heavy, rocky materials to create smaller terrestrial worlds like Earth. But farther away, the solar winds had less impact on lighter elements, allowing them to coalesce into gas giants. In this way, asteroids, comets, planets, and moons were created.

At the starting age, the earth was 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 Jovian planets (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 labelled gas giants.

 

                                    Fig: The Early Earth

 

THE INFANT EARTH

 

The initial Earth was largely molten. Earth's rocky core formed first, with heavy elements colliding and binding together. Dense material sank to the centre, while the lighter material created the crust. The planet's magnetic field probably formed around this time. Gravity captured some of the gases that made up the planet's early atmosphere.

 

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 flow of the mantle beneath the crust causes plate tectonics, the movement of the large plates of rock on the surface of the Earth. Collisions and friction gave rise to mountains and volcanoes, which began to spew gases into the atmosphere.

Collisions from the icy bodies of ice-cold comets leads the water vapor to condensed slowly. The vapours that accumulated in the atmosphere began 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.

Around 70-90 million years ago, our natural satellite, The Moon, came to existence due to the collision of earth with another planet named Theia. This hypothesis is known as the Giant Impact Hypothesis.

                          Fig: Collision of earth with Theia

LIFE ON THE EARTH

Around 3.8 billion years ago, the Archean age began; Archean is Greek for” beginning” or “origin”. During this period cooling of our planet begins until to the point where it was cool enough to sustain and formation of life takes place.

However, life forms weren’t as rich or diverse as they are today. The atmosphere still lacked a layer of ozone and the necessary amount of pressurized oxygen. The mantle was a sweltering 1600° C, which contributed to the planet’s wavering geological activity. Processes like plate tectonics occurred much faster. As the surface continually reshaped itself, continents formed and fell apart.

The movement occasionally led to the formation of a supercontinent. About 750 million years ago, the earliest supercontinent, Rodinia, began to crack and recombined 600 million years ago to form Pannotia, and then finally, Pangaea.

                     Fig: Rodinia

                                       Fig: Pangaea

 

Pangaea broke up 180 million years ago and its components have drifted to form the configuration with which we are currently familiar. Following this was the introduction of humongous dinosaurs, the rise of mammals, the evolution of homo-sapiens and consequently, civilization. All from mere dust.

 

What’s even more tantalizing about the formation of Earth is that the conditions are “just right” for supporting life. We still know very little about how Earth acquired its chemical composition or what – unlike any other planet – allowed it to retain its unique properties.

But science will not rest until we can push our theories back even further in time, to that exact moment when the universe came into being.

SOME FACTS ON THE EARTH

# No one knows who named this planet “Earth”.

# The earth day/night is growing longer year-by-year and 620 million years ago, the Earth day was 21.9 hours.

# If earth didn’t have the moon, our days would only be 6 hours long.

 

 

 

 

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