Erosion caused by rocks and boulders in the base of the glacier acting like a giant file scratching and scraping the rocks below.
(Also called frost-shattering) water enters the cracks during the warmer day and freezes during the colder night. As the water turns into ice it expands and exerts pressure on the surrounding rock, causing pieces to break off.
A type of erosion where melt water in the glacier freezes onto rocks, and as the ice moves forward it plucks or pulls out large pieces along the rock joints.
The impact of aspects of the weather to break down rock INSITU - in cold environments the dominant form of weathering is MECHANICAL OR PHYSICAL.
Physical weathering forces
Such as the wind, freeze thaw and frost shatter can have an impact.
Angular, jagged surface
is left behind by plucking
Large gouges, small striations
Left behind by abrasion of rock against rock which scours the landscape and leave
30m a day
Speed of a glacier in surge conditions, they normally move much slower
Glacial mass balance
the difference between accumulation go snow on a glacier and loss of mass due to melting and evaporation (ablation)
When accumulation (gains via added snow) is greater than ablation (losses through melting and evaporation) leading to growth in ice mass and potential glacial advance down the valley.
Ablation is greater than accumulation leading to a loss of ice mass and the potential retreat of the glacier up valley.
This is where gravity, the mass of the ice and the slope act to make the ice move down slope in a curved or rotational movement.
At the front of the glacier, the snout, the ice shoves material forward. Soil, rocks and boulders are pushed forward by the huge mass of the ice descending the valley.