Cold Environments Unit Revision Cards - Glacial features

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Flashcards by alicenoel, updated more than 1 year ago
alicenoel
Created by alicenoel about 6 years ago
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Includes definitions and formations of galcial features.

Resource summary

Question Answer
Pleistocene The last ice age.
Supra, sub and englacial Supraglacial - on top of the glacier Subglacial - beneath the glacier Englacial - within the glacier
Fjord An overdeepened, drowned valley formed by a glacier overdeepening a pre-existing valley.
Pyramidal peaks 3 cirques backing onto each other.
Seracs Occur at extensional flow points as ice moves over the lip and the glacier begins to travel down the valley
Nunatacks Fromed from physical weathering, they are above the snow and ice fileds and are present in late spring/early autumn.
Rejuvenation When a river adjusts to the new base level (sea level). In this case, following the beginning of a glacial epoch.
The Holocene period 6,000 years ago to the present day.
Bergschrund Between the back wall of a cirque and the ice. It grows as the ice pulls away through weight and gravity from the hollow
Temperate glaciers - Melt in summer - Release huge amounts of meltwater - Forms of movement are: flow, creep, surge, compress, extend - Erode, transport and deposit material
Polar glaciers - In areas where the temperature is always below 0'C - There is no melting, which means slower movement - The galciers are welded to their beds - Internal flow is important - The surface may move faster than the base - Less erosion, transportatino and deposition
Cirques Formed in mountainous areas with high altitudes, they face Nw/Ne, as they recieve less sunlight. The bottom layer of snow is compressed and becomes ice and the hollow is overdeepened - abrasion from plucked rocks. Freeze-thaw shatters the resistant rock. Rotational movement also takes place, as does the formation of seracs.
Valley glaciers Large masses of ice which are often coalescing and flow from the ice fields, following pre-glacial river valleys. Example: Mer do Glace
Piedmont glaciers They are formed when glaciers spread out and they sometimes merge in lowland areas.
Formation of a glacial trough 1: Begins as a 'V' shaped valley 2: Altitude - snow accumulation + cold conditions 3: Snow accumulation - snow fields feed glaciers 4: Onset of ice age - eustatic fall in sea level 5: Drop in sea level - rejuventation of river 6: Rejuvenation means rapid vertical erosion (RVE) 7: RVE starts the overdeepening process and exposes the bare rock of the valley sides, which is RESISTANT 8: The valley walls are then exposed to rapid freeze-thaw weathering 9: Deep weathering - plucking 10: Plucking leads to the widening of the valley. Example: Lauterbrunnen
Where cirques form - Altitude -Nw/Ne -Nunatacks indicate freeze-thaw weathering patters - spring & autumn - Pre-existing hollow - Sloping - Snow line - Resistant, well-jointed rock - About 1000m for the snow line
Glacial budget It is the difference between the total accumulation and the total ablation for one year.
The zone of accumulation The upper part of the glacier, where input exceeds output
The zone of ablation The lower part of the glacier, where output exceeds input
Zone of equilibrium Where the input and output are equal
Fjords - location - 60'N + or 50'S + - Formed in front of mountains which have snow fields, with pre-existing valleys - Prevailing winds are all westerly - longer fetch and so they have more precipitation to feed snow fields - Along coastal margin - High latitude
Fjords - formation: 1 1: Early stages of a glacial epoch, the climate becomes colder, snow accumulates and the sea level falls eustatically. 2: Glaciers are best formed in places with pre-existing valleys that are at a right-angle to each other. 3: Freeze-thaw, plucking and abrasion are necessary for the valley to overdeepen and widen. Rocks entrained into the ice erode the rock beneath. 4: At the head, there is a wall of rock below the water line, where a lip would have moved down. Velocity of the ice increases as it moves down the valley wall so it has more erosive power.
Fjords - formation: 2 5: The sea level has been falling, so the glacier erodes below the normal sea level and the valley overdeepens. 6: The glacier can lose momentum where the coast line is less steep - deposits large amounts of till. This builds up as an undersea deposit or an island at the entrance to the fjord - a threshhold. 7: As the glaciers retreat, the sea level rises, flooding the fjord and causing the meltwater and the seawater to mix. Over 1000s of years material is deposited and the sea water extends along the inlet, so fjords can be tidal.
Lateral moraine Formed from debris which has fallen from the sides of the valley. It has been transported along the edges of the valley and appears as elongated embankments along the sides of the valley.
Medial moraine Where lateral moraines combine when glaciers meet. This may eventually lead to a depositional feature forming once the glacier has retreated. The location of it may be destroyed by fluvioglacial action.
Terminal/end moraine Often a high/series of mounds of debris that extend across a valley. It marks the furthest extent of the glacier/ice sheet.
Recessional moraines Often parallel to terminal moraines, these mark the retreat of the glacier. Each recessional moraine reflects a stage when glacier retreat was halted long enough for deposition to concentrate in one area.
Push moraines These form where a deterioration in climate triggers glacier re-advance and allows earlier moraines to be pushed forward into a new landform. Internally, the orientation of stones may reveal the secondary disturbance they have undergone.
Ria A drowned, overdeepened coastal valley, which formed south of the ice extent.
Rias - formation 1: Formed in NON-GLACIATED areas. 2: Eustatic fall in sea level at onset of glacial epoch. 3: River rejuvenates and erodes to the new base level. 4: Deepest in the middle, where the river originally was. 5: No floodplain - The river eroded to the new base level and was flooded when the sea level rose. 6: At the end of the glacial epoch, the sea level rises and floods the river. 8: Rias are tidal. Example: Kingsbridge in Devon
Ice stages Snow - 10% ice, 90% air (changes with density) | Nevé | Firn | Ice (bluey-green)
System inputs Precipitation Snow avalanches Meltwater Geothermal heat (base of temperate glaciers) Solar radiation Rock debris Gravity
Glacial stores Ice sheets Valley glaciers Piedmont glaciers Niche Cirque/corrie glaciers Snow fields
System outputs Ice-calving Water Sublimation Debris Energy
Drumlins Stoss end - the steep end, lee - the gentler slope. Formed in a glacial landscape when a glacier loses carrying capacity. The glacier moved in the direction from the stoss the the lee end. Formed from shaped and unsorted till, up to 50m in height, 1km in length and no more than 1/2km in width. Shape is preserved by vegetation.
Crag and tail The crag is made from solid rock, at the stoss end, the tail is softer rock. The ice moved in the same direction as with drumlins and left striations on the sides.
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