1. Unit 1: Water Systems on Earth
Grade 8 Science
Unit 1:
Water Systems on Earth

2. Why do We Not Run Out of Water??
Because of the:
WATER CYCLE

3. The Water Cycle...

4. The constant cycling of water through the processes of :
Evaporation&Condensation.condensa tio
Water is constantly changing from
(gas liquid)
and back again. This driven by the sun’s energy.

5. Sources of Fresh Water Lakes, ponds and wetlands Streams and rivers
Ground water
Run Off
Glaciers

6. Glaciers...
A moving mass of snow and ice.
Found in areas where it is so cold the snow remains all year.

7. Glaciers Almost 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
(c) McGraw Hill Ryerson 2007 7

8. Glaciers in mountains and on the continent of Antarctica

9. reach an ocean, where crevasses open and icebergs fall off
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 they
reach an ocean, where crevasses open and icebergs fall off

10. Water trapped in glacial ice

11. Glaciers and Global Warming
In 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.

12. Melting Greenland Glacier

13. Receding Athabasca Glacier in Alberta
It has receded 1.5 km since 1843.

15. What does this mean? Ocean waters may rise Flood rivers
If they disappear, rivers may dry up.

16. Homework
Answer questions 1-5 on p 302
Watch the video-Chasing Ice