- from Oceans
Imagine a rocky planet so hot that all the rocks are a hot, glowing liquid. Thanks to the pull of a giant star, the liquid moves in tides. It swirls around and around the center of the planet. When rain falls, the heat turns the rainwater to steam.
This may sound like another planet, but that’s what the Earth was like, about 4.5 billion years ago. And you probably guessed that the giant star was the Sun.
Scientists don’t know the source of the oceans’ water. Some think the hot rock gave off water vapor, but others think the water came flowing out of the rocks as they cooled.
Later, the rocks and land released salt into the water. Then, very, very slowly, tiny creatures began to form in the water. They took millions of years to develop into the ocean life we see today. Land creatures developed later, evolving from the life forms in the oceans.
Today, Earth has more than 300 million cubic miles of seawater. Most of it has the same amounts of salt and other chemicals.