Scientists think oceans may have formed after millions of years of
What bodies in the solar system collided and combined to form Earth?
Carbon dioxide and water vapor.
Scientists think that earth's first atmosphere was made up of
Gravity and heat.
What factors caused the shape and structure of the earth?
Early life-forms released oxygen into the earth's atmosphere through the process of
The layer of earth that has the lightest elements is the
The middle layer of earth is the
Heavier and lighter elements separated.
Earth's layers formed as rocks melted and
The layer of earth that extends to the planet's center is the