Chapter 10: Glaciation of Canada – page 112-120
Introduction– page 112-114
 250 million years ago, parts of South America, Africa, India, Australia, and Antarctica
were glaciated when they were part of Pangaea. North American and Europe were
not glaciated during this time because they were located closer to the equator.
 Ice age 2 billion years ago, and another 600 million years ago.
 The last Ice Age began between one and two million years ago.
 During the last Ice Age, glaciers advanced and retreated at least four times –
between each period the climate was warm, or warmer, than today.
 These ice ages may have occurred with the changes in the Earth’s orbit around the
sun as well as changes in the tilt of the Earth’s axis, or changes in the heat output
from the sun.
 When the snow does not completely melt in summer we are in a period of glacial
activity.
 Over thousands of years the snow gets deeper and becomes hundreds or
thousands of metres thick. The weight of the snow causes the bottom to turn to ice,
and this glacier can move.
Alpine Glaciers
 In mountainous regions, alpine glaciers move down valleys under the force of
gravity.
 These glaciers scrape away the valley walls as they move and produce U-shaped
valleys.
 Ex. Western Cordillera and the Arctic islands.
Continental glaciers
 Occupy greater areas of land and move outwards under their own weight.
 These ice sheets reached a thickness of 4 km during the last glacial advance.
 Zone of accumulation  See figure 10-21 and 10-22 – page 114
The Glaciation of Canada (page 114-115)
 Glaciation is the process most responsible for Canada’s current topography because
it is an extremely powerful force and it happened recently (in geologic terms) and
there hasn’t been enough time for the glacial features to be worn away.
 See figure 10-23
 Ice compressed the land downward, and when it melted the land rebounded upward.
Erosional Features Caused by Glaciation (page 115-116)
 The Great Lakes were formed by ice gouging out basins of existing lakes.
 As the ice sheets moved they eroded huge amounts of soil, sand, gravel and rock.
This material was carried by ice and it scraped and ground away the surface of the
land.
Grade 10 Geo – Chapter 10 – A. Robinson – December 2006
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 Grooves called striations were often gouged out in the bedrock under the ice sheet
by rocks frozen in the ice. You can see these in the bare rock of the Canadian
Shield.
 These striations run in the same direction as the movement of the ice sheet, and
allow geographers to determine its path.
 Huge volumes of meltwater carved out deep, wide valleys called spillways and
when the ice sheets melted, these spillways became the place of small present day
rivers, called misfit streams.
 See figure 10-25.
Depositional Features Created by Glaciation (page 116-118)
ICE DEPOSITS
 Till – material such as clay, sand, and gravel that is deposited directly by an ice
sheet, with large and small particles together.
 These till deposits under the ice formed a gently rolling landscape called a till plain.
They are good places for growing cops because good soil developed here.
 Moraines – when an ice sheet deposited ridge of till at its edge. These areas are not
good for growing crops because they are thin-soiled, hilly, and swampy. They are
good for grazing and forestry.
 Ice sheets also formed drumlin, an egg shaped hill with a steep side at the wide
end, and a gentle slop on the other. These are good areas to plant crops.
 Erratics – large rocks that were picked up by ice sheets and carried hundreds of
kilometers.
MELTWATER DEPOSITS
 Running water played an important role in the deposition of glacial material. Rivers
flowing within or under melting ice carried sand and gravel along with them and laid
down this material in the river bed.
 Esker – the steep-sided ridge that is left from this material when the ice sheet
melted. Eskers are a source of sand and gravel for the construction industry.
 Moving water deposited larger rock particles in one layer and smaller rock particles
in another layer. You may find a deposit of coarse gravel where a fast moving
stream once existed or silt where a glacial lake once was.
 About 14 000 years ago the climate got warmer and the glaciers began to melt. The
meltwater flowed into lakes, such as Lake Agassiz in Manitoba.
 Lake plains were once the bottom of ancient glacial lakes – they are now used for
agriculture.
 By about 6000 years ago the last Ice Age had come to an end and the Canadian
landscape as we know it was visible.
In Closing (page 119)
 Average yearly temperatures would need to drop only about 4C for an ice age to
occur again.
 It is interesting to note that the dunes known as the "Spirit Sands" were
formed by the melting of glaciers during the Ice Age.
http://www.canadatrails.ca/hiking/mb/sprucewoods.html
DO QUESTIONS 1, 2, 4, 5, AND 6 ON PAGE 120
Grade 10 Geo – Chapter 10 – A. Robinson – December 2006
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