OCR A Level GL - 14 OCR A Level GL 2.4 ALASKA CASE STUDY_ Human Activity changes Periglacial landscape 2 Flashcards
How much proven reserves of oil is in Prudhoe Bay?
3 billion barrels
What is the average daily temperature in northern Alaska in February?
-29 °C
What is the average daily temperature in northern Alaska in July?
8 °C
When was oil discovered in Prudhoe Bay?
1968
When was the Trans Alaskan Pipeline completed?
1977
How long is the Trans Alaskan Pipeline?
1,300km
How many barrels a day does the Trans Alaskan Pipeline transport?
1.4million barrels
What is the name of the ice-free port where the Trans Alaskan Pipeline finishes
Valdez
How many mountain ranges does the pipeline cross?
3
Why was the Trans-Alaskan Pipeline built?
Energy Security
How much did the USA rely on OPEC imports for its oil in 1977?
70%
How successful has Alaskan oil been in providing energy security?
By 2018, the USA only imports about 29% from OPEC countries with Saudi Arabia accounting for only 9%
How are energy flows affected by human activity in Alaska?
- Flaring - raising temperatures 2. Heat Island Effect
How are material flows affected by human activity in Alaska?
- Gravel material - due to gravel extraction, transport and deposition in the river system is being disturbed.
- Hydrological processes - due to gravel extraction, groundwater levels have fallen
What are gravel pads?
a 1-2m thick layer of sand and gravel put underneath infrastructure such as roads, houses and oil rigs
What is the purpose of gravel pads?
to provide an insulating effect to reduce transfer of heat from a man-made structure to the ground. This helps to maintain thermal balance of the ground therefore reducing permafrost thaw and subsidence.
Give a named example of a material flow problem caused by extracting gravel?
On a glacial outwash aquifer near Palmer, ground water levels have dropped by over a metre in an area up to 2km from the gravel extraction site
What have been some solutions to the problems caused by the Trans Alaskan Pipeline?
- Built pipeline on stilts - to prevent melt of permafrost. 2. Designed Thermosyphons which conduct heat from the oil away from the ground - to prevent melt of permafrost. 3. Designed insulation with gravel pads and styrofoam - to prevent permafrost melting 4. Designed Sliders - to provide flexibility to the pipe in the event of an earthquake when it crosses the Denali fault zone
What is a thermokarst landscape?
a landscape dominated by surface depressions (filled with water to form waterlogged hollows) due to thawing of ground ice.
What creates a thermokarst landscape at a regional scale?
a warming climate in a periglacial environment
What creates a thermokarst landscape at a local scale?
Human activity such as removing vegetation or construction which disturbs the thermal balance by removing the insulating layer that protects permafrost.
What are the consequences of a more prevalent thermokarst landscape?
- a thicker active layer 2. more extensive subsidence
What designs are used to reduce the impact of buildings and infrastructure on the thermokarst?
buildings are elevated above the surface to allow air to circulate and remove heat, larger structures and many roads, railway tracks and airstrips are built on gravel pads.
What energy flow problems are caused by flaring?
large amounts of CO2 and methane are released into the atmosphere contributing to the enhanced greenhouse effect - leading to warmer temperatures and further thawing of the permafrost.
What negative local energy flow effect does human activity have on the town of Barrow, Alaska?
human activity has created an urban heat island effect with mean temperatures being on average 2.2oC higher than the surrounding rural areas.
In what ways has human activity in Alaska affected key geomorphic processes in the periglacial environment of northern Alaska?
Heat energy released by human activities (mainly poorly insulated buildings) has resulted in 9% fewer days of temperature fluctuations around 0oc, key for freeze-thaw processes. 90cm thicker active layer (leading to more solifluction) Increased rates of subsidence (from average of 3-4cm/yr to 12cm/yr) which threatens the structural stability of roads, buildings, and pipelines.
How has the population in Barrow, Alaska changed between 1900-2000?
grown from 300 in 1900 to more than 4600 by 2000.
Which landform is created when the active layer thickens on sloped ground?
solifluction lobes
What are solifluction lobes?
When the active layer on sloped ground (as gentle as 1-2°) becomes saturated due to the impermeable permafrost below and moves slowly downslope (between 0.5 - 5cm/year).
What large-scale landscape features are formed due to warming temperatures in periglacial environments?
alases
What are alases?
large scale, steep-sided depressions (5-50m in depth and 100m-15km in length).
What is the average rate of subsidence in North Slope, Alaska?
3-4cm per year
What is the maximum rate of subsidence in North Slope, Alaska?
12cm per year
How thick is the permafrost in North Slope, Alaska?
300-600m
How thick is the active layer in North Slope, Alaska?
30-80cm
