Periglacial Landscapes Flashcards
Where are periglacial environments found? (Give 3 facts)
• High latitude: Arctic regions (e.g., Siberia).
• High altitude: Mountain ranges (e.g., Himalayan Plateau).
• Continental interiors: Cold inland regions away from ocean moderation.
What is permafrost?
Permanently frozen ground that remains at or below 0°C for at least two years.
What are the three types of permafrost?
• Continuous permafrost: Found in the coldest regions, extending to depths of hundreds of metres.
• Discontinuous permafrost: Occurs in slightly warmer areas, with frozen ground up to 35m deep.
• Sporadic permafrost: Only forms in the coldest spots, with patchy frozen ground.
What is the active layer in permafrost? (Give 2 facts)
• The upper layer of permafrost that thaws in summer and refreezes in winter.
• Can become waterlogged and unstable, leading to solifluction and thermokarst formation.
What are the 5 main periglacial processes?
• Nivation: Seasonal snow accumulation encourages frost weathering, deepening hollows.
• Frost heave: Ice lenses form beneath stones, pushing them upwards in the soil.
• Freeze-thaw weathering: Water in rock cracks expands when freezing, breaking the rock apart.
• Solifluction: Saturated soil flows downslope during summer thaw.
• Meltwater erosion: Rapid spring meltwater erodes river banks and transports sediment.
How do ice wedges form? (Mention 3 things)
• Winter: Ground contracts, forming cracks.
• Summer: Meltwater fills cracks, refreezes, and expands, widening the wedge over time.
• Over centuries, these form polygonal ice-wedge networks in permafrost regions.
What is patterned ground? (mention 2 things)
• Stone polygons form when frost heave pushes stones upward.
• Larger stones move outward, while smaller materials fill the centre.
What are pingos? (Mention 4 things)
• Ice-cored mounds up to 100m high and 2km wide.
• Two types:
• Open-system pingos: Form in discontinuous permafrost from groundwater freezing (e.g., Canadian Arctic).
• Closed-system pingos: Form in continuous permafrost when frozen lake sediments force water upward (e.g., Alaska).
What is thermokarst? (Give 2 facts)
• Irregular terrain with water-filled depressions caused by melting permafrost.
• Can lead to unstable ground, damaging infrastructure like roads and pipelines.
What are solifluction lobes and terracettes?
• Lobes: Tongue-shaped deposits formed by flowing saturated soil.
• Terracettes: Step-like features on valley slopes where soil slowly moves downhill.
What are blockfields (felsenmeer)? (Give 2 facts)
• Large angular rock fields created by extensive freeze-thaw weathering.
• Often found on flat plateaus near periglacial environments.
