Shaping of Landscapes by Glaciers
Geography: KS3, topic 10.1.5
Glacial Processes
Glaciers are large ice masses that fill valleys and hollows. A summary of the major glacial processes can be found below:
Freeze-thaw weathering
- Water expands when it freezes. When water fills cracks in rocks, if it then freezes, it expands, putting pressure on the rock. The water will then melt, but it has put pressure on the rock. Eventually, this process of freezing and thawing will wear down rock. This is called freeze-thaw weathering.
- Over time, this causes cracks to widen as the process repeats itself.
Erosion
- Glaciers erode the landscape as they move downhill by:
- Plucking - this happens when meltwater freezes on a piece of rock surrounding the glacier and then rips off bits of rock when it moves.
- Abrasion - this happens when pieces of rock in the ice scrape against rock at the base of the glacier.
Movement and transportation
- Glaciers move in two principal ways:
- Rotational slip - at the top of glaciers, circular motion can erode out hollows, which get deeper over time.
- Bulldozing - at the front of glaciers, rocks and debris are pushed downhill in a straight line.
Deposition
- Most material carried by glaciers comes in the form of unsorted mixtures called till.
- Till is deposited when the ice carrying it melts.
- Meltwater streams can wash away fine material from the front of glaciers. In this case, the material is called outwash and is sorted by size and deposited in layers.
Test yourself on Shaping of Landscapes by Glaciers
The Process of Freeze-Thaw Weathering
What are the two main ways in which glaciers move downhill?