Earth's 4 Spheres

the hydrosphere is made up of all the water on Earth. This includes all of the rivers, lakes, streams, oceans, groundwater, polar ice caps, glaciers and moisture in the air (like rain and snow).

The hydrosphere is found on the surface of Earth, but also extends down several miles below, as well as several miles up into the atmosphere.

The hydrosphere covers about 70% of the surface of the Earth and is the home for many plants and animals.

Most of Earth's water is salty and in the oceans - about 97%. Two-thirds of the remaining 3% is frozen in glaciers and polar ice caps. Only 1% of the hydrosphere is liquid freshwater, and even most of this exists as groundwater down in the soil.

The hydrological cycle transfers water from one state or reservoir to another.

Reservoirs include

• atmospheric moisture
  (snow, rain and clouds)
• streams
• oceans
• rivers
• lakes
• groundwater
• subterranean aquifers
• polar icecaps
• saturated soil

Solar energy, in the form of heat and light (insolation), and gravity cause the transfer from one state to another over periods from hours to thousands of years. Most evaporation comes from the oceans and is returned to the earth as snow or rain

Sublimation refers to evaporation from snow and ice.

Transpiration refers to the expiration of water through the minute pores or stomata of trees.

Evapotranspiration is the term used by hydrologists in reference to the three processes together, transpiration, sublimation and evaporation.

the hydrosphere as a closed system in which water exists. The hydrosphere is intricate, complex, interdependent, all-pervading and stable and "seems purpose-built for regulating life. On earth, the total amount of water has almost certainly not changed since geological times: what we had then we still have. Water can be polluted, abused, and misused but it is neither created nor destroyed, it only migrates. There is no evidence that water vapor escapes into space