glaciated landscapes 6

Question 1

climate change and periglacial areas

Answer 1

periglacial means at or near ice sheets they are defined as areas with permafrost, freeze-thaw cycles or seasonal temperature variations (above 0 in summer). In high latitude and altitude areas periglacial conditions exist.
Types of permafrost: 1 - continuous: frozen all year round, deep permafrost and shallow active layer, high latitudes. Discontinuous: slightly patchy, active layer is thicker (1-1.5m), less deep permafrost, relatively cold.
Sporadic: very patchy and very shallow (12m) permafrost, very thick active layer of soil, slightly warmer temps.

Question 2

geomorphic processes in periglacial areas

Answer 2

1 - Solifluction (mass movement): . Active layer undergoes seasonal thawing, water can’t drain due to impermeable pf so is saturated and moves downhill.
2 - weathering: FTW: water seeps into cracks, refreezes and expands by 10% widening cracks and breaking rocks apart.
3 - nivation: geomorphic processes which occur under a permanent snow patch causing enlargement of hollows.
4 - ground ice: in summer, water percolates into ground. When winter comes, ground near surface freezes causing ice lenses in-between soil layers which draw in water from surrounding sediment via capillary action Ground is pushed up as ice expands 10%.
5 - frost heave: stones heat and cool faster than surroundings due to lower specific heat capacity, when temps fall in stones, water beneath them freezes and expands pushing stones upwards, stones keep getting pushed up.

Question 3

periglacial landforms

Answer 3

1 - patterned ground: frost heave occurs pushing stones to the surface, frost heave causes the surface to be domes so surfaced stones roll down the slope to the edge of the mounds to form circles called stone polygons.
2 - pingos: an ice core covered in soil and vegetation, a dome, 5-50m high. water percolates through talik (in DC PF), groundwater from surrounding slopes collect under gravity on the valley, water rises to the surface due to artesian pressure, when water rises it encounters colder ground and freezes. The ice lens continues to grown due to supply of water. This displaces the sand and gravel above the ice lens to form a pingo.

Question 4

case study: human activity and its effects

Answer 4

Alaska has huge oil fields, the TAP is 800 miles long. . USA depends on imports for 40% of its oil consumption. Prudhoe Bay and oil extraction provides 1/3 of Alaska’s jobs and 20% of their economy.
Effects:
- lodgings constructed for workers, heat from buildings raise ground temps.
- drilling for oil creates heat around boreholes and raises ground temps, gases are released more CO2 in atmosphere.
- airstrips must be built, dark tarmac = low albedo, absorbs more sunlight and raises ground temps.
- dust from gravel roads kill vegetation = less photosynthesis.
- more building and infrastructure: darker surfaces = low albedo so warmer temps in urban areas

Question 5

case study: impacts and consequences

Answer 5

• thawing of permafrost creates an active layer results in saturated material (the PF is impermeable so no infiltration occurs). The saturated active layer can move downslope, it creates solifluction lobes.
• active layer is continuously increasing as permafrost melts, after 25 years it is 7 metres deep.
• formation of thermokrast landscapes: areas of hummocky ground interposed by waterlogged depressions. Occurs when ice in the ground melts causing the ground to collapse and depressions to form.