Glacial Landforms and Landscapes Revision Notes

Glacial processes

    → erosion - plucking, meltwater seeps into rocks, freezes and rocks attach to glacier,         as glacier flows, rocks pulled off, most effective at base of glacier. abrasion - glacier         moves across surfaces, and debris in glacier wear away at rocks.

    → transportation - rockfall, avalanches, debri flows, aeolian deposits (wind), ``              eruptions,plucking, abrasion

    → deposition - lodgement till, material deposited by advancing ice, pressure melts         around objects. ablation till, material deposited by melting ice from stagnant or         retreating ice, rocks are angular and a mix of sizes. 

Weathering processes

    → physical - freeze thaw, water enters cracks, expanding by 10% when frozen. frost         shattering - water trapped in pores freezes and expands.

    → chemical - chemical reaction between water and minerals in rocks, usually                increasing in warmer temperatures.

Mass movement and nivation

    → slides (straight line or rotational) and rock fall

    → nivation - combination of freeze thaw action, transport, and chemical weathering,     causing initial enlargement of corries. 

Erosional landforms

    → corries - glacier erodes hollows through plucking and abrasion, and rotational     abrasion through rotational movement of glacier.

    → aretes - two glaciers form in neighboring hollows, and as erosion continues on     each side, the rock between the corries becomes steeper and narrower (throigh     freeze thaw weathering)

    → pyramidal peaks - aretes developed, and when three or more aretes converge,     they isolate into a central point

    → glacial troughs - during cold periods, glaciers form in a v shaped valley, and     reshape the valley into a u-shape through plucking and abrasion

    → roche motonnee - obstacle at base of glacier, glacier flows over. as the meltwater     melts and refreezes (regelation) it freezes into cracks on the jagged lee side, and as     glacier moves, it plucks. very smooth side (stoss) faces glacier), very jagged side (lee)

    → striations - scratches on roche motonnee, due to abrasion, as stones are dragged     over roche by the glacier

Depositional landforms

    → moraines - terminal moraine, a ridge of till at the end of a glacier, highlighting     where the end of the glacier is. lateral moraine, ridge running along edges of a glacial     valley. recessional moraine, series of ridges running transversely across glacial     troughs, parallel to each other and the terminal moraine.

    → erratics - movement and deposition of one type of rock, to an area where the rock     does not usually exist

    → drumlins - steep, stoss side is upstream, lee tail side is shallow. hypothesis 1: large     rock in centre, glaciers with lots of sediment coalesses around obstacle, creating     stream lined shaped by creation of tail behind obstacle. hypothesis 2: subglacial     sediment deformation, under the glacier, sediemtn is moulded.

    → till sheets - large expanses of thick, unsorted til, deposited by an ice sheet, as it     retreats.