- from Oceans
Imagine a rocky planet so hot that all the rocks are a hot, glowing liquid. The liquid moves in tides, around and around the center of the planet, thanks to the pull of a giant star. When rain falls, the heat immediately turns the rainwater to steam.
This may sound otherworldly, but that’s what our Earth was like, about 4.5 billion years ago. And, as you probably guessed, that giant star was the Sun.
Scientists don’t really know where the oceans’ water came from. Some think the hot, melted rock gave off water vapor, but others theorize that the water flowed out of the rocks as they cooled.
Later, the rocks and land released salt into the water. Then, very slowly, tiny creatures began to form in the water, though it took millions of years for them to become the ocean life we see today. Land creatures developed even later, evolving from life forms in the oceans.
Today, there are more than 300 million cubic miles of seawater on Earth. All over the planet, most seawater contains the same proportions of salt and other chemicals.