Just how was the Earth created? In some fiery furnace atop a great mountain?On some divine forge with the hammer of the gods shaping out of pure ether? How about of a great ocean known as chaos? These all sound familiar? Interestingly enough, these ancient creation stories contain an element of scientific fact to them. When it comes to how the earth was formed, forces that can only be described as fiery, chaotic and indeed, godlike, were indeed involved, though the timeline and buildings materials might have been somewhat different and more complex.
Scientists believe that about one hundred billion years ago the Earth, the Sun, and all the planets of the Solar System were nothing but a cloud of cold dust particles swirling through empty space. Gradually, these particles were attracted to each other and came together to form a huge spinning disk. As it spun, the disk separated into rings and the furious motion made the particles white-hot. The center of the disk became the sun, and the particles in the outer rings turned into large fiery balls of gas and molten-liquid that cooled and condensed to take on solid form. Four or five billion years ago, they turned into the planets that we know today as Earth, Mars, Venus, and the outer planets.
This first eon in which the Earth existed is what is known as the Hadean period, named after the Greek word “Hades” (underworld) which refers to the condition of the planet at the time. During this time, the Earth’s surface was under a continuous bombardment by meteorites, and volcanism is believed to be severe due to the large heat flow and geothermal gradient. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered by comets, accumulated in the atmosphere and cooled the molten exterior of the planet to form a solid crust and produced the oceans. This period ended roughly 3.8 years ago with the onset of the Archean age, by which time, the Earth had cooled significantly and primordial life began to evolve.
As the surface continually reshaped itself over hundreds of millions of years, continents formed and broke up. The continents migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago, the earliest-known supercontinent of Rodinia began to break apart, then recombined 600 – 540 million years ago to form Pannotia, then finally Pangaea, which broke apart 180 million years ago, eventually settling on the configuration that we know today.
We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.