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The Big Bang took place about 13.8 billion years ago and marked the beginning of the universe.
About nine billion years later, the earth was formed. Of course, it was uninhabitable for any life. This age is called the Precambrian Time, which covers about ninety percent of our earth's geological time scale. In this era, the earth's crust separated into several tectonic plates.
The boundaries around these plates, or plate boundaries started to move, some apart, some toward each other. Land on Earth started as one supercontinent, called Pangaea. Over time, due to the theory of plate tectonics and continental drift, we ended up with seperate continents.
But after millions of years of climate change and the atmosphere heating and cooling, the earth developed a solid crust, which has layers, and then plates.
Now, we are on a rocky earth, where according to the law of superposition, the oldest layers of rock are farther down in the Earth's crust. Most of the entirety of the fossil record has been found in these layers.
Once the earth's climate got to a sustainable level, cyanobacteria appeared in our oceans. These were the first entities to undergo photosynthesis. The atmosphere became rich with oxygen, and our ozone layer was formed.
All of the rock on this Earth is classified into three categories: Sedimentary, which is compressed through many years of pressure and heat.
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