glaciated landscape Flashcards
whats glacier mass balance
the difference between the amount of snow and ice accumulation and the amount of ablation occurring in a glacier over a one year period
cold based glaciers
- low altitude
- low relief
- basal temperatures below the pressure point
- very slow rates of movement, perhaps a few meters/cm a year
warm based glaciers
- high altitude locations
- steep reliefs
- basal temperatures alter above the pressie melting point
- rapid rates of movement, typically 20-200 m/year
what are the open systems
means energy and matter can be transferred from neighbouring systems as an input. it can also be transferred to neighbouring systems as an output
whats a input
energy eg kinetic energy from wind
material from deposition weathering and mass movement from slopes
whats an output
glacial and wind erosion
evaporation
whats equilibrium
when a systems outputs and inputs are equal
whats dynamic equilibrium
when the equilibrium is disturbed, the system produces its own response to the disturbance. this response is an example of negative feedback
whats ablation
refers to all processes that remove mass from a glacier
what are the two key aspects that influence glaciated landscape systems
lithology and structure
whats lithology
describes the physical and chemical composition of rocks. for example some rocks such as clay have a weak lithology, with little resistance to erosion.
whats structure
concerns the properties of individual rock types such as jointing, bedding and faulting. it also includes the permeability of rocks.
high altitude
- beyond the artic and antarctic circles
- 66.5 degrees north and south
- tend to have cold dry climates with little seasonal variation in precipitation
low altitude
- high precipitation inputs
- variable temperatures
- more summer melting
what is relief
the term used for the differences in height from place to place on the land’s surface
effects of relief
the steeper the relief of the landscape the greater the resultant force of gravity and the more energy a glacier will have to move downslope.
whats aspect
the direction that a slope faces
effect of aspect
if the aspect of the slope faces away form the general direction of the sun, temperatures are likely to remain below zero for longer as less solar energy is received and so less melting occurs.
how does glacial ice form
glaciers form when temperatures are low enough for snow that falls in one year to remain frozen throughout the year. this means the following year fresh snow falls on top of the previous years snow.
each new fall of snow compresses and compacts the layer beneath, causing the air to be expelled and converting low density snow into higher density ice
what are valley glaciers
Valley and piedmont glaciers originate in the high alpine and terminate on land. They often flow through deep bedrock valleys that confine the ice on either side. Over time, they carve and shape these valleys (see U-Shaped Glacial Valleys)
why do glaciers move
- due to gravity
- the gradient, the steeper the gradient of the ground surface the faster the ice will move if other factors are excluded
- the thickness of the ice, as this influences basal temperature and the PMS
factors that influence the movement of glaciers
- gravity, the fundamental cause of the movement of an ice mass
- gradient, the steeper the gradient of the ground surface, the faster the ice will move if others factors are excluded
- the thickness of the ice, as this influences basal temp and the pressure melting point
- the internal temperatures of the ice, as this can allow movements of one area of ice relative to another
- the glacial budget, a positive budget (net accumulation) causes the glacier to advance
whats glacier mass balance
the difference between the amount of snow and ice accumulation and the amount of ablation occurring in a glacier over a one year period
what are niche glaciers
are small patches of ice found on upland slopes. they are most prevalent on north facing slopes in the northern hemisphere, they have relatively little effect on topography
what are cirque (corrie) glaciers
are small ice masses on mountain slopes which gradually erode armchair shaped hollows. if they develop to be too large for the hollow, they spill over the lip to feed into a valley glacier.
what are valley glaciers
large masses of ice that flow from ice fields or a cirque and usually follow periglacial river valleys, developing steep sides as they erode on course. this erosion is known as a U shaped valley
what are Piedmont glaciers
large lobes of ice when glaciers spread out. they may merge on reaching lowland areas and escape the confines of their U shaped valley
what are ice caps
they are huge flattened, dome shaped masses of ice that develop on high plateaus. they are similar to an ice sheet, but are less than 50,000km2 in area. (above 50,000km2 are ice sheets)
what are ice shelves
extensions of ice sheets that reach out over the sea. these shelves of floating ice can be up to 1km thick but diminish to around 500meters at the edge where the ice breaks off. this process if known as ‘calving’
why do glaciers form
snow compacts as new snow falls on top and turns to glacial ice
when does compression flow occur
occurs where there is a reduction in the gradient of the valley floor leading to ice deceleration and a thickening of the ice mass. at such points ice erosion is at its maximum
when does a creep occur
occurs when stress builds up within a glacier, allowing the ice to behave with plasticity and flow. it occurs partially when obstacles are met
when do surges occur
occurs from time to time when an excessive build up of meltwater under the glacier leads to the ice moving rapidly forward, perhaps by as much as 250-300 meters in one day.
what is basil flow
as the glacier moves over the bedrock there is friction. the lower ice is also under a great deal of pressure and this, combined with the friction, results in some melting. the resulting meltwater acts as a lubricant, enabling the ice to flow more rapidly
when does rotational slip occur
occurs within a corrie (cirque or cwm), the birthplace of many glaciers. here ice moving downhill can pivot about a point, producing a rotational movement. this combined with increased pressure with the rock hollow, leads to greater erosion and an over deepening of the corrie floor.
when does extended flow occur
occurs when the valley gradient becomes steeper. the ice accelerates and becomes thinner leading to reduced erosion
when does internal flow occur
occur when ice crystals orientate themselves in the directions of the glaciers movement and slide past each other. as surface ice moves faster, crevasses develop.
whats the geomorphic process of freeze thaw
water enters crack and expands by nearly 9 percent when it freezes. in confined spaces this exerts pressure as the rock causing it to split into pieces or break off. PHYSICAL/MECHANICAL
whats the geomorphic process of frost shattering
at extremely low temps, water trapped in rock pores freezes and expands. this creates stress which disintegrates rock to small particles. PHYSICAL/MECHANICAL
whats the geomorphic process of pressure release
when the weight of overlaying ice in a glacier is lost due to melting, the underlaying rock expands and fractures parallel to the surface. this is significant in the exposure of sub surface rocks such as granite and is also known as dilation. PHYSICAL/MECHANICAL
whats the geomorphic process of oxidation
sine minerals in rocks react with oxygen in air or water. iron is especially susceptible to this process. CHEMICAL
whats the geomorphic process of carbonation
rain water combines with dissolved carbon dioxide from the atmosphere to produce a weak carbonic acid. CHEMICAL
whats the geomorphic process of solution
some salts are soluble in water, any process by which a mineral dissolves in water is known as solution (PH around 3) CHEMICAL
what is the geomorphic process of tree roots
tree roots grow into cracks or joints in rocks and exert outward pressure. BIOLOGICAL
what is the geomorphic process of organic acids
produced during decomposition of plant and animal litter cause soil water to become more acidic and react with some minerals called chelation
whats endogenic
beneath earth surface
whats exogenic
on earth surface
what are the two key types of mass movement
rock fall and slides
whats rock fall
on slopes of 40 degrees or more, especially if the surface is bare, rocks nay become detached from the slope by physical weathering processes. these then fall to the foot of the slope under gravity. Transport processes may then remove this material, or it may accumulate as a relatively straight, lower angled scree slope.
what are slides
occurs when a portion of the soil or rock along a steep slope suddenly gives away and moves downhill, usually aided by heavy rainfall. Sliding mass movement occurs on slopes weakened by weathering such as landslides, rockslides, and mudslides.
what are the 4 types of mass movement
fall, slide, flow and creep