Water is one of the most indispensable natural resources on Earth. The Earth is called the Blue planet because it holds water in abundance. The hydrosphere consists of water in all its forms on the Earth. This lesson covers fresh water, the oceans, the relief of the ocean floor, waves, tides, ocean currents and marine resources.
1. Hydrosphere and the Hydrological Cycle
- Over 97% of the water on the Earth's surface is in the oceans; less than 3% is held on land as glaciers, ice caps, groundwater, rivers and lakes, and as water vapour in air.
- The continuous movement of water on, above and below the Earth's surface is the Hydrological Cycle.
- Its three major processes are evaporation, condensation and precipitation; water constantly changes form – ice, water and water vapour.
- Water resources are broadly divided into fresh water and salt water.
2. Fresh Water
- Rain water is considered the purest form of water, as it has very little salt – hence fresh water.
- A major part of fresh water is frozen in ice caps and glaciers; around 1% is liquid in rivers, streams, lakes and ponds.
- Surface water that penetrates porous rocks and collects underground is groundwater.