2.2.2
Periglacial Landforms
Ice Wedges and Patterned Ground
Ice Wedges and Patterned Ground
Periglacial environments, such as northern Canada and northern Russia, have a range of characteristic landforms, including ice wedges and patterned ground.
Ice wedges
Ice wedges
- Ice-wedge polygons are generally 20–30 m across.
- They are formed in areas of continuous permafrost by ground freezing in the winter and thawing in the summer.
- When temperatures fall in winter, water in fissures in the active layer freezes and so expands, pushing the ground apart.
- The wedge shape is maintained as water further down from the surface, over 3m down, remains frozen.
- The annual repetition of this process causes the gradual formation of marked ice-wedges which develop in polygonal patterns.
Patterned ground
Patterned ground
- Stone polygons are smaller than ice-wedge polygons, less than 10 m across and are the result of frost heave.
- During the winter, soils freeze downwards from the surface, reaching and ‘grabbing’ individual stones, which are pulled upwards by the expansion vertically of the frozen soil above them.
- The empty space left beneath is filled with loose unfrozen soil, so the stone is prevented from moving back when the soil below freezes.
Patterned ground cont.
Patterned ground cont.
- Stones are also pushed towards the surface because of the pressure of small ice lenses growing beneath them.
- Stones warm up more quickly so, in the summer, the ice in the soil beneath the stone melts, allowing wet sediment to slump to fill the space beneath it.
- This prevents it from sinking back into its original position.
- As the stones collect on the surface of the ground, the larger stones are pushed towards the edge of the pile by ground expansion. Gravity and smaller stones, sands and silt are left in the middle, resulting in a polygonal shape.
Pingos
Pingos
Pingos are domed mounds of layered sediments with a core of ice and are usually up to 100 m in diameter. They can be as wide as 2 km.
Open pingos
Open pingos
- Pingos can be open or closed.
- Open pingos can be seen in the Canadian Arctic and Siberia and are more likely to be found in clusters.
- Open pingos are formed in areas of discontinuous permafrost when groundwater from small areas of talik moves upwards because of an increase in hydraulic pressure as the active layer re-freezes in winter.
- As the water freezes near the surface, it causes the ground surface to dome upwards, forming the characteristic shape of a pingo.
Closed pingos
Closed pingos
- Closed pingos are less common and are found in Alaska and Greenland.
- Closed pingos are formed in areas of continuous permafrost when water pushed down from frozen lake sediments accumulates at depth, freezes and then expands again, causing the ground surface to dome.
- Some pingos have a small depression at their top, resulting from localised melting there.
1Tectonic Processes & Hazards
1.1Tectonic Processes & Hazards
1.2Natural Disasters
1.3Natural Disaster Case Studies
1.4Trends & Patterns
2Option 2A: Glaciated Landscapes & Change
2.1Glaciated Landscapes Over Time
2.2Periglacial Landscapes
2.3Glacial Processes
2.4Glacial Landforms
3Option 2B: Coastal Landscapes & Change
3.1Coastal Landscapes
3.2Coastal Erosion & Deposition
3.3Coastal Risks
4Globalisation
4.1Globalisation
4.2Negatives of Globalisation
4.3Global Shift
4.5Culture
4.6Measuring Development
5Option 4A: Regenerating Places
5.1Types of Economies
5.2Function of Places
5.3Regeneration
5.4Regeneration Case Studies
6Option 4B: Diverse Places
6.1Population Structure
6.2Past & Present Connections
6.3Urban & Rural Spaces
6.4Diversity
6.5Urban & Rural Case Studies
6.6Case Study - Tower Hamlets
6.7Case Study - Sturton-le-Steeple
7The Water Cycle & Water Insecurity (A2 only)
7.1Hydrological Processes Global to Local
7.2Influences on the Water Cycle
7.3Water Insecurity
8The Carbon Cycle & Energy Security (A2 only)
8.1The Carbon Cycle
8.2Energy Consumption
8.3Alternative Energy
8.4Growing Demand for Resources
9Superpowers (A2 only)
9.1Superpowers
9.2Hard & Soft Power
9.2.1Hard & Soft Power
9.2.2Emerging Powers - China Rivalry
9.2.3Emerging Powers - Chinese Sources of Power
9.2.4Emerging Powers - Brazil
9.2.5Emerging Powers - Russia
9.2.6Emerging Powers - India
9.2.7Theories of Development
9.2.8Power Case Studies: Chinese One Belt One Road
9.2.9Power Case Studies: Pakistan Nuclear Arms
9.2.10Power Case Studies: OPEC
9.3IGOs, TNCs & Alliances
10Option 8A: Health & Human Rights (A2 only)
10.1Human Development
10.2Role of Governments & IGOs
10.3Human Rights
10.4Interventions
11Option 8B: Migration & Identity (A2 only)
11.1Globalisation & Migration
11.2Consequences of Migration
11.3Nation States
11.4Responses to Global Migration
Jump to other topics
1Tectonic Processes & Hazards
1.1Tectonic Processes & Hazards
1.2Natural Disasters
1.3Natural Disaster Case Studies
1.4Trends & Patterns
2Option 2A: Glaciated Landscapes & Change
2.1Glaciated Landscapes Over Time
2.2Periglacial Landscapes
2.3Glacial Processes
2.4Glacial Landforms
3Option 2B: Coastal Landscapes & Change
3.1Coastal Landscapes
3.2Coastal Erosion & Deposition
3.3Coastal Risks
4Globalisation
4.1Globalisation
4.2Negatives of Globalisation
4.3Global Shift
4.5Culture
4.6Measuring Development
5Option 4A: Regenerating Places
5.1Types of Economies
5.2Function of Places
5.3Regeneration
5.4Regeneration Case Studies
6Option 4B: Diverse Places
6.1Population Structure
6.2Past & Present Connections
6.3Urban & Rural Spaces
6.4Diversity
6.5Urban & Rural Case Studies
6.6Case Study - Tower Hamlets
6.7Case Study - Sturton-le-Steeple
7The Water Cycle & Water Insecurity (A2 only)
7.1Hydrological Processes Global to Local
7.2Influences on the Water Cycle
7.3Water Insecurity
8The Carbon Cycle & Energy Security (A2 only)
8.1The Carbon Cycle
8.2Energy Consumption
8.3Alternative Energy
8.4Growing Demand for Resources
9Superpowers (A2 only)
9.1Superpowers
9.2Hard & Soft Power
9.2.1Hard & Soft Power
9.2.2Emerging Powers - China Rivalry
9.2.3Emerging Powers - Chinese Sources of Power
9.2.4Emerging Powers - Brazil
9.2.5Emerging Powers - Russia
9.2.6Emerging Powers - India
9.2.7Theories of Development
9.2.8Power Case Studies: Chinese One Belt One Road
9.2.9Power Case Studies: Pakistan Nuclear Arms
9.2.10Power Case Studies: OPEC
9.3IGOs, TNCs & Alliances
10Option 8A: Health & Human Rights (A2 only)
10.1Human Development
10.2Role of Governments & IGOs
10.3Human Rights
10.4Interventions
11Option 8B: Migration & Identity (A2 only)
11.1Globalisation & Migration
11.2Consequences of Migration
11.3Nation States
11.4Responses to Global Migration
Unlock your full potential with GoStudent tutoring
Affordable 1:1 tutoring from the comfort of your home
Tutors are matched to your specific learning needs
30+ school subjects covered