Glaciated landscapes case studies- physical systems

Glaciation:

Glaciated upland area originated 18,000 years ago.

Ice accumulates on higher, cooler slopes. Due to gravity, this ice fell to fill the former river valleys. During the glacial period the ice cap was surrounded by other glaciers and therefore the easiest route for the ice to follow was that of former river valleys.

Erosional Landforms:

Corries (Llyn Llyolow), aretes, pyramidal peaks, u-shaped valley (Nant Ffrancon), truncated spurs, ribbon lakes (Llyn Ogwen).

Depositional Landforms:

Till (englacial, subglacial, supraglacial), errarics.

Glacitation:

75,000 years ago, lobes of ice extended from the Laurentian ice sheet- these lobes advanced and retreated many times transporting and depositing till.

Erosional impact:

Over 1km thick in places with great erosional impact. Mountains worn down to create elipsoidal basins. Ice lobes also created striations in rocks.

Depositional impact:

Wadena lobe deposited red sandy till and alexandria moraine in the drumlin fields in Otta Tail. The last advance of the rainy and superior lobes left a course till containing basalt, red sand stone and slate.

Pro-glacial lakes:

The edge of the ice sheet dammed drainage creating pro-glacial lakes. eg. Lake Agassiz. This happened when the glaciers to the north blocked natural drainage. 

Hayday:

Prudhoe bay. The 795 mile long transalaska pipeline has transported over 12.8 billion barrels of oil. - 2 million barrels/day in 1988.

Needed because: 40% of US oil comes from imports which is a concern as no energy security.

Impacts on peri-glacial systems:

Gravel is extracted from rivers as a base layer for construction- alters the ersional and depositional processes in the river. Energy flows are effected by flaring (the release of gas during drilling) and heat produced from extraction and transportation.

Changing landforms

Heat released during oil extraction melts the active layer and thaws the permafrost.

Thermokarst:-Landscape depressions due to thawing of ground ice.                                 Alasses= flat floored steep sided depressions from wide spread thawing.

The dam:

HEP powerplant storing 400 million m^3 water each year. Half from 35 glaciers. Water stored drives four power stations and generates 2000 GWh annually powering 400,000 households. Due to this, less than 5% of Swizerland's energy comes from fossil fuels.

Impacts on glacial systems:

Water is stored behind the dam leading to deposition of sediment. 15% of the water in the dam is used to flush out the 20-40cm of sediment each year.

Impacts on river channels:

The flushing of sediment causes more erosion in river channels as the water used has excess energy. There is also an increased risk of flooding in Val d'Heren when the excess water is released which has hindered the tourist development.

Impacts on the environment:

Pumping stations are largely underground with minimal impacts.