You’ve heard the saying that the Earth is mostly water, but exactly what percent of the Earth is water? Salt water oceans make up 71% of the Earth’s surface, while the other 29% consists of continents and islands. But there are also freshwater lakes and glaciers that cover the Earth’s surface.
Of all the water on Earth, 97.5% is contained within the oceans, while the remaining 2.5% is freshwater lakes and frozen water locked up in glaciers and the polar ice caps. Almost 69% of the fresh water on Earth is ice. If you could melt all the water on Earth, and the Earth’s surface was perfectly smooth, the water would rise to an altitude of 2.7 km.
But what percent of the Earth is water? Not just the surface of the Earth, but the actual mass of the planet? Scientists calculate that the total mass of the oceans on Earth is 1.35 x 1018 metric tonnes, which is 1/4400 the total mass of the Earth. In other words, while the oceans cover 71% of the Earth’s surface, they only account for 0.02% of our planet’s total mass.
We’ve written many articles about the oceans for Universe Today. Here’s an article about how many oceans there are, and here’s an article about why the ocean is salty.
We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.