Hydrosphere. When we think of the earth, we think mostly of areas of land. However, the land actually makes up only a small part of the world. Water, or the hydrosphere, makes up most of the earth’s surface. The hydrosphere consists of all bodies of water and ice, plus water vapor in the atmosphere. We see the hydrosphere mostly in the basins of lakes and oceans. In some parts of the Pacific Ocean, the hydrosphere is more than 6 miles (9.7 kilometers) deep.
The hydrosphere resembles another part of the earth, the atmosphere, because it is fluid and its pressure and temperature change at different depths. Oceanographers find that even in tropical oceans, the temperature at great depths is just a few degrees above freezing.
More than 97 per cent of the hydrosphere’s volume is salt water contained in the world’s seas and oceans. About 2 per cent of the hydrosphere’s volume consists of ice stored in the polar icecaps. Less than 1 per cent is fresh water found in lakes, rivers, and such forms of ground water as that in caves, geysers, springs, and wells. Water vapor in the atmosphere makes up only one-thousandth of 1 per cent of the hydrosphere.
The water on the earth’s surface contains many dissolved solid materials. These solids come from the rocks and soil with which the water comes into contact. Salt water has a high content of sodium chloride, or ordinary table salt. Fresh water contains dissolved solids in far smaller amounts.
