A-Level Geography: Glaciation Keywords
Internal deformation
A 'creep' method found generally in cold-based glaciers where the ice crystals orientate themselves in the direction of movement. This allows ice crystals to slide past one another.
Benchmark glacier
A glacier chosen to be monitored annually for ablation and accumulation
Rock glacier
A glacier covered by a layer of scree/talus or a mass of rock and debris mixed with ice; forms a glacier like landform
U shaped valley
A hanging valley where tributaries must drop down into the glaciated valley floor, produced by erosion and the chopping of mountains due to glaciation
Loch Lomond Stadial (Younger Dryas)
A period of time (12.9k yrs ago - 11.7k yrs ago) where global average temperatures decreased by 7 degrees, causing glacial advancement which reached as far as the Lake District and North Wales. No known cause of event, however, it is thought that this may have been caused by the draining of a huge proglacial lake (Lake Agassiz) which dramatically effected global ocean circulation
Little Ice Age
A period of time (1550-1750) where global temperatures decreased, this caused glacial re advancement in in Europe, spread of arctic sea ice (reaching Iceland). Bodies of water all over the world froze over including the Thames and the New York harbour, however, it was brought to an end by the industrial revolution
Orbital/Astronomical forcing
A process which can change the amount of energy from the sun reaching the Earth and forces climate to change as a response
Patterned ground
A range of geometric landforms including circles, nets, polygons and steps. Caused by frost-action, this is in the form of frost push and frost heave, causing mass-movement on the surface
Blockfield/Felsenmeer
A surface covered by boulders, rocks and debris; formed by frost weathering below the surface leading to jagged, angular rocks on the surface
Milankovitch cycle
A theory that suggests that changes in the Earth's climate are caused by variations in solar radiation received at the Earth's surface. These variations are due to cyclical changes in the geometric relationship between the Earth and the Sun. It comes in three parts: orbit eccentricity, axial tilt and Earth wobble
Tarn
A type of glacial lake where water fills a corrie
Equilibrium point
Ablation losses and accumulation gains are balanced within a glacier
4.6 billion years
Age of the Earth
Discharge
Amount of water flowing downstream, measured in Cumecs
Resistive Stress
Caused by friction, greatest at bottom and sides of glacier (all points of contact)
Sheer stress
Caused by the mass of glacier, greatest in centre of glacier
Ice sheet
Complete submergence of regional topography; forms a gently sloping dome of ice several kilometres thick in the centre
Transverse Crevasses
Cut across glacier, perpendicular to the direction of flow
Solar spots
Dark spots on the Sun's surface caused by intense magnetic storms
Plucking
Erosive process of particle detachment by moving glacial ice. In this process, basal ice freezes in rock surface cracks. As the main body of the glacial ice moves material around, the ice in the cracks is pulled and plucked out. Also called quarrying
Glacier
Flowing sheet/river of ice
Solifluction
Form of mass movement in environments that experience freeze-thaw action. It is characterised by the slow movement of soil material downslope and the formation of lobe-shaped features
Discontinuous permafrost
Form of permafrost that contains numerous scattered pockets of unfrozen ground
Continuous permafrost
Form of permafrost that exists across a landscape as an unbroken layer
Sporadic permafrost
Form of permafrost that exists as small islands of frozen ground in otherwise unfrozen soil and sediments
Radial Crevasses
Found at the Piedmont where cracks radiate from the centre of the glacial spread
Marginal Crevasses
Found at the sides of a glacier, caused by differences in the rate of flow (as glaciers flow fastest in the middle)
Ice wedge polygons
Frost cracking creates areas of irregular polygons, where the active layer thaws, water flows down into the cracks and subsequently freezes building up a wedge and raising the ground around it
Valley glacier
Glacier confined between valley walls and terminating in a narrow tongue; forms from ice caps/sheets or cirques; may terminate in sea as a tidewater glacier
Glacial distribution
Greater snow cover in high altitudes and greater values of latitude
Corrie
Hollow in mountain-side, arm-chair shaped landform
Pingo
Ice core mounds, very large (30m-70m high), can be conical or elongated. The growth of a core pushes up sediment, forming mounds
Ice field
Ice covering an upland area, but not thick enough to bury topography; many do not extend beyond highland source
Cirque
Landform created by glaciers, grinding an existing valley into a rounded shape with steep sides, often called a corrie or cwm
Ice shelf
Large area of floating glacier ice extending from the coast where several glaciers have reached the sea and coalesce
Ice Field
Large level area of glacial ice found covering a large expanse of land. Similar in size to an ice cap but does not have a dome shape
Névé or firn
Partially melted and compacted snow that survives the year's ablation season (it can become glacier ice)
Glacial Period
Period of time during an ice age when glaciers advance because of colder temperatures
Interglacial Period
Period of time during an ice age when glaciers retreat because of milder temperatures
Pleistocene
Period of time from about 2 million years ago to 11,700 years ago. During this period areas of land at higher and middle latitudes where covered with glacial ice
Abrasion
Physical wearing and grinding of a surface through friction and impact by material carried in water or ice
Nivation
Process where snow patches initiate erosion through physical weathering, melt-water flow and gelifluction
Interstadials
Short-term changes to conditions that lead to ice
Stadials
Short-term changes to conditions that lead to ice re-advances
Cirque glacier
Smaller glacier occupying a hollow on the mountain side- carves out a corrie or cirque; smaller version is known as a niche glacier
Ice cap
Smaller version of ice sheet occupying upland areas; outlet glaciers and ice sheets drain both ice sheets and ice caps
Causes for short term fluctuations of temperature
Solar spots and volcanoes
Arêtes
Steep ridges between corries
Ablation
Surface removal of ice or snow from a glacier or snowfield by melting, sublimation, and/or calving
Albedo
The amount of light or radiation that is reflected by a surface such as ice
Calving
The breaking up of the ice sheet at the glacier snout which then forms icebergs
Eccentricity
The change of the Earth's orbit from circular to elliptical
Anthropocene
The current geological age, the period during which human activity has been the dominant influence on climate and the environment
Cryosphere
The frozen water part of the Earth system
Scree/Talus Slopes
The loose debris on the face of a mountain, a product of rock fall, debris flow and avalanches
Thermohaline circulation
The ocean consists almost entirely of water and salt . The density of water depends on its temperature and salinity. Any changes to this causes the water to flow (currents). Also known as ocean conveyor
Atmosphere
The part of the Earth system consisting of air and anything above the surface
Hydrosphere
The part of the Earth system consisting of water, such as lakes, seas, oceans and clouds
Biosphere
The regions of the surface and atmosphere of the Earth occupied by living organisms
Lithosphere
The rigid outer part of the Earth system, consisting of the crust and upper mantle
Basal Sliding
The sliding of a glacier over the surface it rests on. Caused by the gradient of the slope and the weight of the glacier's mass. Comes in two forms: relegation slip and enhanced basal creep
Permafrost active layer
The top level of soil of permafrost that thaws and freezes during summer and winter
Precession
The wobble of the earth
Obliquity
Tilt of the earth varies between 22.2 and 24.5, the greater the tilt, the more solar energy the Earth receives
Lithology
Type and properties of an area's rock
Talik
Unfrozen ground
Piedmont glacier
Valley glacier which extends beyond the end of a mountain valley into a flatter area and spreads out like a fan
Icehouse conditions
Very cold glacial conditions
Greenhouse conditions
Warmer interglacial conditions
Soft-bed subglacial deformation
When a bed of rock is unconsolidated and the sediment itself deforms and moves along with all ice above it. Can account for 90% of forward motion
Loess
When glaciers grind rocks to a fine powder the wind can transport the fine, mineral-rich material and deposit it creating a new soft rock that is loosely packed and pale in colour. It can range in thickness from a few centimetres to more than 91 metres (300 feet)
Intergranular flow
When individual ice crystals deform and begin to move in relation to each other
Laminar flow
Where individual layers of the glacier move
Truncated Spurs
Where interlocking spurs have been chopped off by the glacier
Tors
where more resistant areas of rock are left; uneroded stacks of smooth rock