Chapter 10: Water Systems on Earth

Transcription

1 Chapter 10: Water Systems on Earth

2 The Hydrosphere Water covers 70% of the Earth 3 % of the Earth s water is fresh only 1/3 of that is liquid (rest is frozen glaciers) therefore, only 1% of Earth s water is available as drinking water

3 Water Distribu;on Most drinkable water is underground ( groundwater ) the rest is either in lakes or streams ( surface water ) or in the atmosphere (precipitaion/ clouds)

4 The Water Cycle water changes states as heat is added or taken away the driving force behind this cycle of heat on Earth is the sun.

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6 Types of Water Ocean water: high salt content Fresh water: low salt content

7 Salinity Salinity - the amount of salt dissolved in water salinity is high close to the equator (high evaporaion) and poles (salt lep behind when water freezes) salinity is lower near coninents (diluted by fresh water from rivers)

8 Why are the Oceans Salty? When water moves through the ground, it picks up dissolved solids These solids are carried with the water to the ocean, where they have built up over billions of years Volcanic erupions also add more material to the oceans

9 Proper;es of Sea Water Most common dissolved solids: sodium and chlorine (together, make salt ) Salt water is more dense than fresh water Salt water freezes at a lower temperature than fresh water

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11 Fresh Water Resources Fresh water is available from three main sources: Surface water run- off Ground water Glaciers

12 Surface Water Run- Off Rainwater/snow melt forms run- off the flow of water over ground to rivers or other water bodies The water flows due to gravity

13 The amount of run- off depends on: Ground material Amount of rain Length of rainfall Slope of the land VegetaIon Amount of development

14 Drainage basin: the area in which any rain that falls will flow to a paricular stream A divide separates one drainage basin from another Reservoirs are human- made or natural lakes that store water for human use

15 Glaciers 2/3 of Earth s fresh water is trapped in large masses of snow and ice called glaciers glaciers form when more snow falls than melts every year, causing it to build up over Ime

16 Glaciers Large ice sheets, called coninental glaciers, cover both the Earth s poles, in Greenland and AntarcIca Alpine glaciers form in mountain areas, and slowly slide down the mountain due forces of gravity

17 Water s Effect on Shaping the Earth s Surface Weathering the process of breaking down rocks into smaller fragments Erosion the transport of rock fragments from one locaion to another Deposi;on the se\ling of rock fragments in a new locaion

18 Weathering There are three types of weathering: Physical Chemical Biological

19 Physical Weathering rocks are broken down by physical means (there is no change in the chemicals making up the rock) Ice Wedging Water fills cracks in rocks, then freezes As water freezes, it expands and pushes the rock apart.

20 WeLng and Drying Physical Weathering Clays swell and shrink, causing rocks to fall apart. Wind and water effects Wind and water move sand and small rocks around, rubbing them against each other unil they gradually wear into smaller fragments.

21 Chemical Weathering Rocks are broken down by chemical reacions, which causes the rocks to change their composiion and become weaker. Chemicals in rain, snow and air break down some minerals in rocks. Some minerals react with water to form clays (hydrolysis).

22 Chemical Weathering Oxygen from air combines with iron in some minerals to form rust (resuling in red soil - oxida;on). Many minerals, such as limestone and marble, dissolve easily in weak acids such as rainwater. Rainwater is usually slightly acidic because carbon dioxide dissolves in it to form carbonic acid. Acid rain forms stronger acids which can speed up the rate of chemical weathering.

23 Biological Weathering If physical or chemical weathering has been caused by a plant or animal, the process is someimes referred to as biological weathering. Plant seeds or roots may grow in Iny cracks in rocks. As the plant grows, it cracks the rock. Burrowing animals move rocks around and can expose new rock surfaces to weathering. Rocng vegetaion forms acids which also lead to chemical weathering.

24 Moving Water Erosion sediment (bits of weathered rock) can be carried long distances by moving water before being deposited at another locaion Gravity sediments on slopes slowly work their way downwards by the force of gravity if wet soil and rock on a slope becomes too heavy, landslides may result

25 Glaciers Erosion as glaciers move, they scrape and erode the ground beneath them scratch marks, called striaions, are lep on rocks over which a glacier passed.

26 Deposi;on moving water and glaciers can also deposit the materials they pick up

27 Referring to page 397 in your workbook, describe each of the following