The oceans are an important part of Earth: they help to determine the make-up of the air, they help determine the weather and temperature, and they support great amounts of life. The composition of ocean water is unique to its location and depth. Just as Earth’s interior is divided into layers, the ocean separated into different layers, called the water column.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.