What is a Glacier?
Rock cycle – breaks down and moves rock
Water cycle – glacier store large amounts of water
Glacier trap water for a long time
If all the ice in glaciers melted, the sea levels would
rise 70 m
Alpine Glaciers:
 A glacier that forms high above sea level where
temperatures stay cold in summer keeping last
winter’s snow from melting. This lets snow and ice
build up.
 Most alpine glaciers are found in mountains
Continental Glaciers
 Ice sheets are huge plates of ice that build up and
bury the land
 Examples of ice sheets are in Greenland and the
Canadian High Arctic
Glacial Ice:
Firn: old snow that has been recrystallized into
a more dense glacial ice
 Glacial ice looks blue because it is dense and
reflects blue light
 White ice usually looks that way because of air
bubbles
Laurentide Ice Sheet:
 This was a large continental glacier
It started from central Keewatin and extended all
the way west to the Tuktoyaktuk Peninsula
It covered the land from 36000 BP to 20000 BP
Retreat of the Laurentide Ice Sheet:
 They scraped the bedrock, making valleys and leaving
boulders and piles of silt as they melted
They made all the lakes that are a part of our
northern landscape
Only two continental sized ice sheets left on earth:
Greenland and the other in Antarctica
Many active alpine glaciers in the mountain regions in
the North
 Glaciers are fed by snowfields of the high mountain
ranges
Glaciers are made of a main ice body with smaller
tributaries
How are Glaciers Formed?
 They start as snowflakes
 It takes time for snow to turn into glacial ice
 Glaciers only form when it is cold enough for snow to
stay without melting for several years
 New layers of snow buries and compacts the snow
 Melting and refreezing compact it even more.
Microscopic Views
- Freshly fallen snow: individual snowflakes are visible
and many air pockets
- Snow changes over time: snowflakes become rounded,
larger, denser and more compact
- Air is squeezed out of the snow to the surface or into
bubbles
Macroscopic Views:
- Firn: old snow that has been recrystallized into a more
dense glacial ice
- Pressure from 70-100 m of snow and firn layers above
compresses firn into bubbly ice
- Deeper in the glacier the air bubbles in the ice are
absorbed, creating true ice
- It takes 25-100 years to change snow to glacial ice