Flashcards in systems and processes in glaciers and glacial landscapes Deck (70)
the natural removal of snow or ice from the surface of a glacier or snowfield. this can occur through melting, sublimation or calving
breaking of ice chunks from the edge of a glacier
Sublimation is the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage.
the addition of snow or ice
the lowest elevation on mountains where snow remains year-round
the side of the mountain that is exposed to sunlight
the side of a mountain that is not exposed to direct sunlight
it is when lower levels of snow are compresses by the upper levels as snow accumulates making it very compact (forms after two seasons of accumulation). solid ice develops after 20-40 years after all the air has squeezed out.
zone of accumulation
the upper part of the glacier where inputs exceed outputs and therefore more mass is gained than lost over a year.
zone of ablation
where outputs exceed inputs in the lower part of the glacier, and mass is lost rather than gained
the boundary between the zone of accumulation and ablation
where net gain and net loss is balanced - the equilibrium line.
difference between total accumulation and total ablation in 1 year.
When accumulation exceeds ablation - Snout moves downwards
When ablation exceeds accumulation - Snout move upwards
Cold periods in Earth's history when glaciers have advanced and ice sheets increased in size
The warm periods that occur during ice ages or between ice ages
Glacial area in europe
Are most glaciers retreating?
Yes but some in Alaska and the Himalayas are advancing.
3 types of glaciers
Temperate/warm based, polar/cold based and sub-polar
Where are warm based glaciers located?
In temperate and alpine regions with high winter snowfall rates and spring/summer temperatures high enough to cause rapid summer melt rates.
Where are cold based glaciers located?
Found in areas of high latitude within the Arctic and Antarctic circles and in cold areas of Alaska and Canada. Low precipitation and aid conditions
The characteristics and development of temperate/warm based glaciers
Large amounts of meltwater which acts as a lubricant, faster rates of movement --> more erosion, transportation and deposition. The surface (thin layer - few metres) melts rapidly and insulates the layers of ice beneath it. Lower melting point at base of glacier due to high pressure (pmp). Temperate glaciers can be relatively thin so more ice influenced by geothermal heat
Pressure melting point (pmp)
The temperature at which ice under pressure will melt. At the base of a 2000m deep glacier the melting point is -1.27C
The characteristics and development of polar/cold based glaciers
Little accumulation, virtually no melting. Ice at base can be 100,000 years old. All ice except the most upper surface layers that can be exposed to summer temperatures is below the melting point. Little meltwater due to little geothermal and atmospheric heat. Most ice loss is due to sublimation and ice calving. Frozen to bedrock to v slow movement (mainly internal flow) - little erosion, transportation and deposition
A change directly from the solid to the gaseous state without becoming liquid.
The breakdown and/or decay of rock at or near the earth's surface creating regolith (debris) that remains in situ until it is moved by later erosional processes. Can be chemical, mechanical or biological (very little in cold environments due to low temps)
Frost action (freeze-thaw action) - frost shattering
Occurs when temps exceed 0C during the day but drop below freezing at night. Water enters cracks in rock and freezes overnight and expands by <10% which exerts pressure on surrounding rock. This process repeats which widens cracks and breaks off rock. This can collect at the bottom of a slope (scree slope) with scree at the bottom
A vertical or nearly vertical shaft in a glacier, formed by surface water percolating through a crack in the ice.
Series of processes that operate underneath patches of snow in hollows. Freeze-thaw action and chemical weathering causes underlying rock rock to disintegrate. As some of the snow melts in spring the weathered particles are 'flushed out' of the hollow and moved downslope by meltwater and solifluction. This repeated process forms nivation hollows which can be the beginnings of a corrie