EQ3 - how do glacial processes contribute to the formation of glacial landforms and landscapes Flashcards
How do glacial troughs/u shape valley ( erosional landform) show evidence of past ice extent And any issues ?
On some u-shaped valley sides it is possible to identify a trim line - below this line you can see evidence of glacial abrasion,such as striations and polished rock surfaces. The trim line indicates the extent and height to which the glacial trough was filled with ice
However only shows localised glaciation and limitation if the glacier is going through compressional extensional flow.
How do rouche mountonnee ( erosional landform) show evidence of past ice movement And any issues
We can always identify the smooth stoss and jagged lee. Indenting the lee to see direction of ice movement. Micro scale striations show direction as they are parallel to ice flow.
Striations can be mistaken with chatter marks which are perpendicular to ice form and difficult to identify in the field.
How does terminal moraine ( depositional landform) show past ice extent ? And any issues
a crescent shaped mound or ridge of moraine found at the snout of the glacier and which represents the furthest advance of the ice
Moraine can be difficult to indenting in the field due to later glaciation
How does drumlins ( depositional) show past movement of ice ? And any issues
oval-shaped hills, largely composed of glacial drift, formed beneath a glacier or ice sheet and aligned in the direction of ice flow.
We can map a drumlin field by identifying the stoss and the lee we can identify where the ice is moving.
Many drumlins are altered or destroyed by human activity through farming,construction of infrastructure and urbanisation,reducing the value of this technique. For example Glasgow is built on a drumlins field these fields have been disturbed by the development of transport routes. Therefor they need to be studied more for accurate reconstruction
How do eskers ( Fluvio-glacier) show past ice movement And any issues
a long narrowing ridge of Fluvio- glacial sand and gravel. A subglacial stream can carry large amount of rock debris due to their high hydrostatic pressure inside tunnels. The streams often meander beneath the glacier. When the glacier retreats, the debris load is deposited at a consistent rate and forms a ridge.
Assuming meltwater and ice flow are the same direction. As it meanders can be altered by weathering
How do outwash plains ( Fluvio glacial) show past ice extent ? And any issues
a flat expanse of Fluvio-glacial debris in front of the glacier snout as meltwater streams emerge from the glacier and enter lowland areas, they gradually lose their energy and deposit debris load. Gravel is deposited first closest to the glacier then sand and finally clay
Difficult to measure as it’s a vast area of land
Easily affected by post glacial activity
What is a kames ?
found on the surface. A kame is a deposited mound of sediment left in the path of a retreating glacier.
1) rock falls from the valley on top of the glacier the sediment then falls into crevasses in the glacier
2) Deglaciation occurs the crevasses move closer down to the base as the glacier melts
3) when they reach the valley bed once the glacier has almost melted they are dumped onto the bed as a mound of sediment
What are kame terraces ?
results from the infilling of a marginal glacial lake. When the ice melts, the Kane terrace is left as a ridge on the valley side
What are kames deltas ?
are smaller features that form when a stream deposits material on entering a marginal lake. It forms small mound like hills on the valley floor
What are kettle holes ?
A circular depression,often forming a lake in an outwash plain. As the glacier retreat’s detached blocks of ice remain on the outwash plain. Meltwater streams flow over the ice,covering them in deposits of Fluvio- glacial debris. Eventually the ice melts and the debris subsides to form a depression with often fills with meltwater forming a kettle hole lake
What is a proglacial lake
a lake formed in front of the glacier snout it’s often formed by the damming action of a moraine during the retreat of a melting glacier.
what is freeze thaw weathering
water enters cracks
over night it freezes
water frozen the volume increases by 9%
this then creates cracks ad evetually breaks rocks
what is glacial crushing
this is the direct fracturing of weak bedrocks through the weight of ice above it. for this to occur the bedrock must be weakened. by either freeze thaw or repeated glacier advance and retreat causing dilation
what is basal ice melting
beneath the temperate glaciers can produce large volumes of meltwater causing erosion processes, abrasions,hydraulic action. subglacial meltwater travels at high speed and pressure because it is confined beneath the glacier
what is glacial plucking /quarrying
underneath the glacier meltwater gets into cracks and freezes. the ice attaches and locks itself to the rock. AS the ice moves forward it pulls the rock out. this rock then found on the bedrock as sub glacial
