When the Earth was formed 4.6 billion years ago, it would
never have been called the Blue Planet.
There were no oceans, there was no oxygen in the
atmosphere, and no life.
But there were violent collisions, explosions, and
eruptions. In fact, the Earth in its earliest stage was molten.
This allowed elements to separate into layers within the
Earth — gravity pulled denser elements toward the Earth’s
center, while less dense materials accumulated near the
surface.
This process of separation created the layers of the Earth as
we know them. As temperatures cooled, the surface solidified and an
atmosphere was created.
Volcanic eruptions released water vapor from the
Earth's crust,
while more water came from asteroids and comets that
collided with the Earth.
About 4 billion years ago, temperatures cooled
enough for oceans to begin forming.