Grade 8 ScienceGrade 8 ScienceUnit 1:

Water Systems on Earth

Why do We Not Run Why do We Not Run Out of Out of

Water??Water??Because of the: WATER CYCLE

The Water Cycle...The Water Cycle...

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.

Sources of Fresh Sources of Fresh WaterWater1. Lakes, ponds and

wetlands2. Streams and rivers3. Ground water4. Run Off5. Glaciers

Glaciers...Glaciers...A moving mass of snow and ice.

Found in areas where it is so cold the snow remains all year.

(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

Glaciers in mountains and on the continent of Antarctica

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

Water trapped in glacial ice

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.

Melting Greenland Glacier

Receding Athabasca Glacier in Alberta

It has receded 1.5 km since 1843.

What does this What does this mean?mean?Ocean waters may rise

Flood riversIf they disappear, rivers may dry up.

HomeworkAnswer questions 1-5 on p 302

Watch the video-Chasing Ice