water_presentation.pptx 1º ESO OXFORD UNV PRESS

ABCD

1. THE BLUE PLANET OCEANS AND SEAS INLAND WATER WATER HAZARDS WATER ON EARTH

2. 1. The blue planet The hydrosphere is all the surface and underground water on Earth. 97% of Earth’s water is salt water in seas and oceans. Only 3% is fresh water, which is essential for life on Earth. The water cycle Water is continuously changing state. Condensation Precipitation Evaporation Infiltration

3. 2. Oceans and seas The oceans are large bodies of salt water between the continents. Seas are smaller bodies of salt water that are closer to the continents. Do oceans and seas move ? Oceans and seas are constantly moving for various reasons: Gravitational pull of the Moon Wind moving across the surface Tectonic plates colliding Ocean currents constantly flowing through oceans and seas.

4. 3. Inland water UPPER COURSE MIDDLE COURSE LOWER COURSE Source Mouth River It is a permanent flow of water that moves downhill and into a sea. A river can be regular : its flow is the same throughout the year. Alternatively, it can be irregular if it changes with the seasons. The flow rate of a river depends on the amount of rainfall and the type of river basin . Inland water is water on the surface of the continents or under the ground. It’s usually fresh water.

5. 3. Inland water Groundwater About 30% of Earth’s fresh water is under the ground. Water filters through the soil and the cracks and spaces in porous rock . When it reaches impermeable rock , it forms an aquifer . If an aquifer becomes saturated, groundwater can return to the surface at a spring . Ice Almost 70% of the Earth’s fresh water is frozen in glaciers , ice caps or permafrost .

6. 4. Water hazards Floods Heavy rainfalls Rapid snowmelt Strong storms Extreme weather events Droughts Long periods of low rainfall Desertification Soil loses its fertility and becomes unproductive for agricultural use Human overuse of water resources in agriculture and industry also contributes to desertification.