The Formation of the Earth: Creating Our Home
Born from the storm, comes anger and rage;
we all go through a rebel phase.
Planet Earth has existed 4 billion years ago. That’s a pretty substantial period of the age of our 13.8 billion-year-old Universe. However, you would not have recognized it in its first billion years. It was a strange molten hellscape filled almost entirely with lava and occasional solid islands of rock. It was completely uninhabitable, almost everything we associate with the Earth – air, water, life had not yet emerged. Even once the earth was formed, it took a while to get to our little blue oasis. Let’s dive in, to the early Earth.
Formation of the Earth
The Earth formed in the same way that our galaxies, our Sun, and every other planet in the solar system formed – through dust slowly clumping together through gravity. The differences were – the earth is a lot smaller, so it was really only formed by the leftover bits of dust that didn’t fall into our Sun. Secondly, the material that formed the earth and nearby planets, was a bit different from the material that formed the stars, as most of it was rock and metal, as opposed to the gas that burns in our Sun. This would have made the process a bit quicker as rock is a fair bit heavier (see our formation of the solar system post).
The solid outer layer of the Earth formed pretty quickly. At first, Earth was basically just a planet of lava with occasional rocky islands, with a surface temperature of 2800 degrees. However, within 100 million years, the earth cooled to about 100 degrees celsius and the outer earth solidified into the rocky ground, called “the crust” that we walk on today. The evolution of the internal bits of the Earth, the liquid metallic bits (called the “core” and “mantle”) are not as well understood, but probably happened afterwards.
The Earth is still a far way off being something we’d recognize, particularly with regard to the atmosphere and oceans. The earliest atmosphere on the earth was basically just leftover space gases from the dust in the solar system. It was similar to what Jupiter and Saturn have today and was very thin, and was rapidly lost into space. Oceans were also still not a thing at this stage. The earth needed to cool significantly below 100 degrees Celsius before that could occur (see the next post).
The Moon: The big dust-up
The formation of our Moon is a particularly exciting bit of our Universal history. Our current best guess for how the Moon formed is called the ‘Giant Impact Hypothesis’ where the Earth was hit by a giant asteroid, which knocked off a big chunk of the planet, which spun around in orbit for a while until eventually forming the moon we know and love. The asteroid has been named ‘Theia’. The Pacific Ocean is probably what’s left of the creator it caused.
The theory isn’t universally accepted, but it is certainly our best current guess. Our Moon is made of almost the exact same kind of rock that the earth is, which is a bit different from the stuff that makes up the other planets. Our Earth and Moon are both also moving very quickly compared to other planet and moon systems in our solar system, so it’s quite possible that they both just recently got hit by something moving very quickly recently. Our Moon is also a fair bit bigger than the moons of other planets (think Jupiter and Saturn and all their little tiny moons), so it’s quite likely something a bit different happened to create our Moon, compared to the other Moon’s in our solar system.
Asteroids: The Heavy Bombardment
There was still a fair bit going on in the Solar System early on in the Earth’s history. There were a lot more asteroids and rocks floating around, they hadn’t been gathered up into nice little asteroid belts yet (Jupiter did us a real big favour there – our post about it here). And these asteroids very often hit the newly formed planets. There was one particular period from about 4.2 to 3.8 billion years ago called the ‘Heavy Bombardment’ known for having a particularly intense period of asteroid impacts.
These asteroid impacts were quite important for the development of our Earth. As a general rule, the really heavy elements of metal that were on the Earth from the beginning are deep within the core. This is because heavier elements on the earth, while it was all molten and liquid tended to sink (because they were heavier). If it wasn’t for the impact of these asteroids, there would be much less metal on the surface of the earth– and this would have made it much harder for life and chemically complex things to evolve on earth.
So the Earth was weird for a bit? So what?
The Earth seems a pretty tame place today. Don’t get us wrong, there are some storms and deserts and harsh places. But compared to its early days and to most of the Universe it’s pretty comfortable. It gives us a nice atmosphere, a nice temperature and keeps everything just right for us.
But it wasn’t always, it was initially hot and hellish. It already took so much time to get galaxies and stars in the Universe. Then, even more, to get our Sun and our Earth to form took so much more. And then, even when the earth was in the right place and the right time, it took the Earth a billion years to cool and get to be a vaguely habitable planet.
It just took so much to get here. We’ll talk about it more next post how the earth got oceans and an oxygen atmosphere. But we here at The Universal Story, think knowing about this early angry earth, really makes you appreciate how lucky we are, to have our Earth as it is today. Maybe we should treat it a little better.
