Landforms of glacial erosion - Glacial troughs Flashcards
What do glacial troughs develop from?
They develop from a pre-existing valley system within which the underlying rocks have been affected by jointing and weathering, often in combination with regional faulting.
What must the underlying rocks have been affected by in the pre existing valley system in order for a glacial trough to develop?
They should have been affected by jointing and weathering, often in combination with regional faulting
What impact does regional faulting have on trough walls
Regional faulting is often responsible for the distinctively straight trough walls in some regions.
What is the impact of the occupation of the valley system by ice?
The occupation of a valley system by ice modifies the pre-existing relief to form the characteristic straight glacial trough associated with highland glaciations.
Which 3 processes combined remove any protuberances in both a lateral and vertical erosion to form a steep sided glacial trough?
Freeze-thaw weathering
Abrasion
Plucking
Why has the classic U shape of glacial troughs in the UK been significantly modified?
They have been modified post glacially by fluvial processes, mass movement, chemical and biological weathering.
Why is the parabolic U or trough shape efficient?
It is efficient for the evacuation of large volumes of ice
The uneven nature of the floor of the glacial trough is a function of what?
It is both a function of varying rock resistance and variation in the intensity of erosion.
In areas of compressional flow ice movement is characterised by what?
In areas of compressional flow, ice movement is characterised by the rotational movements also seen in cirques causing increased abrasion and the creation of a hollow called a rock basin
On either side of the basin what happens to the more resistant rock?
Its eroded less
These outcrops of harder rock are known as rock bars.
What do rockbars do?
Rock bars act as dams between which rainwater may accumulate after the retreat of ice, filling up the rock basin and creating a larger ribbon lake or a series of smaller paternoster lakes.
