Glacial Processes
Geography: AQA GCSE, topic 3.4.2
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 Glacial Processes
Freeze-Thaw Weathering
What are the 2 main ways in which glaciers move downhill?