Glacial and Periglacial Environments
Glacial and Periglacial Environments
This domain tests glacier mass balance, glacial erosion and deposition, landform identification, periglacial processes and the interpretation of past glacial change. Strong answers use process-landform links and evidence from maps.
Core rules
- Mass balance is accumulation minus ablation. Positive balance means advance; negative means retreat. Retreat does not mean the ice flows backwards.
- Warm-based glaciers slide and erode by plucking and abrasion; cold-based glaciers are frozen to the bed and erode less.
- Erosional landforms include cirque, arete, pyramidal peak, U-shaped valley, hanging valley, truncated spur and roche moutonnee. Depositional landforms include till plains, lateral, medial, terminal and recessional moraines, drumlins, eskers and kames.
- Periglacial environments are near ice sheets but not ice-covered: permafrost, active layer, solifluction, patterned ground, pingos and nivation are key.
- Landform evidence indicates ice direction and extent, but must be interpreted with care.
Worked example
A valley has a broad U-shaped floor, steep sides, truncated spurs and a small stream. Explain this landscape. Reasoning: glacial erosion widened and deepened the valley, truncated interlocking spurs, and left steep rock walls. The misfit stream is underfit because post-glacial discharge is much lower. A V-shaped valley with interlocking spurs would indicate fluvial erosion instead.
Traps
Do not confuse U-shaped and V-shaped valleys. Do not label all moraine as terminal. Do not treat periglacial as under ice. Do not confuse the drumlin stoss (blunt) end with the lee (tapered) end.