grade 8 science unit 1: water systems on earth. why do we not run out of water?? because of the:...
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Grade 8 ScienceGrade 8 ScienceUnit 1:
Water Systems on Earth
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Why do We Not Run Why do We Not Run Out of Out of
Water??Water??Because of the: WATER CYCLE
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The Water Cycle...The Water Cycle...
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The constant cycling of water through the processes of :
Evaporation&Condensation.condensatio
Water is constantly changing from
(gas liquid) and back again. This driven by the sun’s energy.
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Sources of Fresh Sources of Fresh WaterWater1. Lakes, ponds and
wetlands2. Streams and rivers3. Ground water4. Run Off5. Glaciers
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Glaciers...Glaciers...A moving mass of snow and ice.
Found in areas where it is so cold the snow remains all year.
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(c) McGraw Hill Ryerson 2007
GlaciersAlmost 66% of all fresh water on Earth is
in glaciers◦Glaciers form from layers of snow falling over
many years◦Glaciers melt slowly under their own weight,
and slowly flow downhill◦Glaciers cover about 10% of the Earth’s
surface◦Alpine glaciers (aka valley) found in mountains◦Continental glaciers (aka ice sheets) cover
huge areas of land. Eg. Greenland and Antarctia
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Glaciers in mountains and on the continent of Antarctica
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Glaciers slow down the Water Cycle by storing big amounts of frozen fresh water. Some water thaws in the hot summer months.
They give us information about the Earth’s past climates. ( samples) ◦ Glaciers flow until theyGlaciers flow until they
reach an ocean, where crevasses open and icebergs fall off
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Water trapped in glacial ice
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Glaciers and Global Glaciers and Global WarmingWarmingIn the last 100 years the average surface temp. Has increased by 0.5oC.
The world’s glaciers are melting at a quicker paces than ever before.
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Melting Greenland Glacier
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Receding Athabasca Glacier in Alberta
It has receded 1.5 km since 1843.
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What does this What does this mean?mean?Ocean waters may rise
Flood riversIf they disappear, rivers may dry up.
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HomeworkAnswer questions 1-5 on p 302
Watch the video-Chasing Ice