15863765
| Question | Answer |
| CORRIES | Armchair-shaped hollow Upland hills/ mountainside Steep back wall, over-deepened basin and often a lip at the front (solid rock/ morainic deposits) |
| Size | Some only a few hundred metres across but can be over 15km wide Walcott Corrie Antarctica over 3km back wall |
| Formation: | Several interaction processes |
| 1 | Nivation of small hollow on hillside in which snow collects and accumulates year on year |
| 2 | Hollows enlarge and contain more snow > compresses into névé and then glacial ice Hollow gets bigger due to movement (abrasion) Plucking creates a steep back wall Pressure release de-stresses and weakens rock Abrasion at base of hollow using material from freeze-thaw weathering and plucking |
| 3 | At a critical depth the ice acquired a rotational movement under its own weight Basal slippage = regelation slip, creep and rotational flow Rotational flow requires meltwater for lubrication - warm-based glacier Highest rate of erosions at base due to rotational flow and thickness of glacier |
| 4 | Bergschrund = large tensional crevasse formed where moving ice splits away from stagnant ice due to rotational movement Leaves rock face exposed so freeze-thaw can continue Debris from plucking and weathering above hollow falls into bergschrund > helps to abrade hollow causing it to deepen |
| 5 | Thinner ice at the front unable to erode so rapidly so higher lip is left May also consist of moraine deposited by the ice as it come out if the corrie Extending flow - ice flows into valley due to steep gradient to velocity increases (thin so less friction) |
| 6 | Post-glaciation the Corrie May become filled with a small circular lake = a tarn |
| Arrête | Narrow, steep-sided ridge found between 2 corries Steepening of slopes + retreating corries back to back/ alongside Striding Edge Lake District |
| Pyramidal peak | 3 or more corries develop around hill or mountain too and back walls retreat Matterhorn Swiss alps over 1200m high |
| TROUGHS | Has a stepped long profile Steep gradient: Faster velocity > ice spreads out (thinner) > extending flow > less erosion Low gradient in rock basin: Slow velocity > ice builds up > compressing flow > more erosion |
| Formation: | Path carved by glaciers in (entire length of U-shaped valley) |
| 1 | Glacial ice moves through pre-existing river valley > erode sides + floor through abrasion and plucking so becomes deeper, wider and straighter |
| 2 | Creates U-shaped valley Parabolic due to weathering + mass movement > scree slopes lessen angle after glacier retreats Flat valley floor due to post-glacial alluvium |
| 3 | Compressing flow - enhances abrasion Alternating bands of hard and soft rock > differential rates of erosion > weaker rock eroded to form basins, harder left as rock step Ribbon lakes may form in basin |
| Size: | U-shaped valley width 0.5 to 3km |
| ROCHE MOUTONNÉE | Projections of resistant rock on the floor of glacial troughs |
| Size: | 1-5m high 5-20m long |
| Formation: | - |
| 1 | Localised pressure melting on up-valley side as advancing ice passes over them Smoothed and streamlined + often striations due to abrasion |
| 2 | Down-valley side pressure reduced - meltwater re-freezes > plucking and steepening Steep + jagged Can indicate direction ice moved |
| ELLIPSOIDAL BASINS | Formed by ice sheets |
| Formation: | Ice sheet eroded areas Bands of softer rock led to over-deepening Meltwater fills dépressions forming lakes as glacier retreats Weight of ice led to isostatic lowering of the landscape |
| Size: | Laurentide ice sheet north America: Began to form end of last glacial period 14,000 years ago Master basin holds Hudson Bay Smaller basins contain the Great Lakes - Lake Superior average depth 147m |
| STRIATIONS | Scratches made on rock by debris embedded in base of glacier Parallel to ice flow |
| Formation: | As glacier moves through basal slippage (warm-based glacier) |
| Glacial grooves | Larger e.g. Kelleys Island Ohio Up to 3m deep For significant grooves rocks carried in glacier hard geology compared to landscape |
| Chatter marks | Crescent shaped gauges chipped out of bedrock as glacier drags rock fragments underneath Perpendicular to flow Commonly found with striations |
| HANGING VALLEY | Tributary glaciers left in smaller valleys high above shrunken central glacier surface > after glacier melts |
| Formation: | Smaller tributary glacier less erosive power so differential erosion Larger main valley erodes quickly cutting valley deeper When glacier retreats smaller valley left hanging further up > waterfalls may form |
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