Earth Science: Water on the Earth
The name of our planet may not be the most appropriate since only 29 percent of the Earth’s surface consists of land, while 71 percent is covered by water. Composed of two hydrogen atoms and one oxygen atom, water is one of the most important resources on Earth and is essential for living organisms.
Ocean saltwater accounts for about 97 percent of the estimated total water quantity of 34 million cubic miles (1.45 billion km3). The oceans are the origin of all life as well as the largest biosphere on Earth. Most freshwater—the only kind of water that is drinkable—is trapped inside polar ice caps and high mountain glaciers, while some freshwater collects in standing or running water bodies.
Water is continuously in motion and it circulates the planet in the form of enormous ocean currents.