The Very Beginnings
Around 4.6 billion years ago, our solar system was made of dust and gas called a solar nebula. The gases started to spin like a disk, creating the sun we know today. Some scientist believe that the Earth also formed within the disk, other scientist think that the remaining particles clumped together after the sun was formed.
A hot, rocky center formed first, then others layers built on top. Denser layers, made of iron and nickel sank to the center while the lighter layers came to the top. Over the next millions of years, Earth's gravity pulled gases from space closer to earth, creating our atmosphere.
The Evolution of Earth
As the earth cooled, a crust formed on the surface. Because the core of the earth was still a liquid, the crust was able to shift, creating tectonic plates. When plates collided, mountains and volcanoes formed. A stray planet hit the earth sending pieces of the earth into space. Some pieces got trapped by earth's gravity, creating the moon.
Icy comets hit earth frequently, covering the earth in ice, then melting into water. With an abundance of liquid water and carbon dioxide, conditions were right to support life.