WATER IN THE OCEANS
- SALT WATER: oceans and seas cover 71%of the earth´s surface . Most of the water on the planet is salt water. Rivers and rain carry rocks and minerals to oceans and seas ; this makes thm saline. Not all seawater hast the same salinity. Water in landlocked seas and in warmer latitudes is usually saltier, because the heat causes more evaporation than in open and cold seas.
- WATER IN MOVEMENT: Seawater is constantly moving because of the movement of curents, tides and waves. This movement erodes and shapes coastlines. Ocean currents are like big rivers moving within the oceans. The water in these currents does not mix with the rest of the sea because it has a different temperature or salinity. Currents can be warm or cold. Tides are the rising and falling of sea levels. They are caused by the gravitational forces of the Moon.
- RIVERS AND LAKES: A river is a moving stream of water. The flow of a river is the amount of water it carries. The water in rivers comes from rain, sprngs and melted sonw. A river flow can change during the year. Lakes are permanent bodies of water. The water in lakes comes from rain, rivers and groundwater.
- GROUNDWATER: is water that collects or flows under the earth´s surface. When it rains, some of the water penetrates the ground and collects in aquifers. These underground lakes feed rivers on the surface. Groundwater maintains the flow of rivers and keeps the soil damp.
- ICEBERGS AND GLACIERS: Most of the fresh water on earth is frozen solid. The cryosphere includes all the ice in the world. Most of its is in polar icecaps. The rest is in glaciers on high mountains.
- WATER IN THE ATMOSPHERE: Our atmosphere contains water in the form of water vapour. Most water vapour is found in the lower part of the atmosphere, the troposphere.