The hydrosphere includes all water on, under, or above a planet’s surface, with 70.8% of Earth’s surface covered by water. Life on Earth is dependent on the hydrosphere, and the water cycle is a key process. Ice sheets make up 77% of global freshwater, but are melting due to global warming.
The hydrosphere refers to all of the water that is on, under, or above a planet’s surface. In physical geography, it usually refers to the water on or around planet Earth, although Jupiter’s moon Europa is thought to have a subsurface ocean. Sometimes, this term also includes the cryosphere, or all of the ice on the surface, in which case it would include Mars, which has ice caps.
About 70.8% of the earth’s surface is covered by water, with 97% sea water and 3% fresh water. Water is also found in significant portions in the atmosphere, which is thought to be about 1% water vapor. The oceans, with an average depth of 12,447 feet (3,794 m) – five times deeper than the average height of continents – are thought to have a total weight of about 1.35 × 1018 tons, or about 1/4400 of the total mass of the Earth .
Life on Earth (biosphere) is strongly interdependent on the hydrosphere. Where there is little water, only a few extremophile microbes can survive. Where water is abundant, there are huge forests and biological diversity. Some of the wettest areas on Earth are rainforests, which contain two-thirds of the planet’s biodiversity, despite making up only 2% of the earth’s surface.
A key process in the hydrosphere is known as the water cycle, whereby water evaporates from the oceans, rains down on mountains and flows back to the sea. The water cycle contains many little quirks and patterns, such as the sublimation of water on land and the storage of water in underground aquifers. Underground aquifers are so huge and abundant that they hold enough water for hundreds of years.
Ice sheets, which cover large portions of Antarctica and Greenland, make up about 77% of the global freshwater total. Due to global warming, many of these layers are melting, causing the levels of the world’s oceans to slowly rise.
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