Depositional landforms Flashcards
Lateral moraine
Material deposited at the flanks of a glacier
Occurs when the glacier comes into contact with the valley side causing friction. This causes the glacier to reduce in velocity and ablate material as it is unable to carry it.
Parallel to movement of glacier
Medial moraine
Sediment deposited in between two glaciers.
When two glaciers come together, friction is produced which reduces the velocity of the glacier. This causes the glaciers to deposit the sediment it is carrying. Marked by a dark ridge
Terminal and recessional moraines
Terminal moraines are found at the maximum ice extent. Ablation causes deposition to form ridges where the snout is.
Recessional moraines show the extents of glacier retreats and advancements but don’t mark the final ice extent. Shows where glacier ablates, causing deposition. Perpendicular to ice flow
Deposition: ablation
Erratic dumping of material from portion of glacier
Deposition: fluvioglacial
Deposited when meltwater channel loses velocity, usually heaviest sediment deposited first
Deposition: lodgement
Beneath ice mass when subglacial debris being transport becomes ‘lodged’.
Occurs when friction between subglacial debris and bed becomes greater from drag of ice
Ablation till v fluvioglacial till
Ablation till-angular, poorly sorted, coarse
Fluvioglacial-rounded, well sorted, fine
Drumlins
Smooth, elongated mounds of till with long axis parallel to direction of ice movement
Steep stoss, gentle lee
Elongation ratio=l/w
Occur in swarms (basket of eggs)
Differ to roche moutonees as vegetated, gentle lee and steep stoss
Menzies theory 1979
Drumlins formed when glacial sediments are deposited when the glacier becomes overloaded
Shaw theory 1989
Drumlins show evidence of sorted fluvioglacial till sediment, indicating meltwater formation
