glacial deposition Flashcards
(8 cards)
moraines
landforms associated with deposition of till from within, on top, and below a glacier
-consists of porrly sorted, mainly angular sediments
-medial, lateral, recessional, terminal morains
terminal moraines
ridge of sediment piled up at furthest extent of advancing ice glaicer
-commonly appears as line of hills instead of solid ridge, due to erosive action of meltwater streams from retreating glacier
recessional moraine
-retreating glaciers may experience periods of stability, when a secondary ridge of sediment forms at snout
-has same characteristics as terminal moraines, but doesn’t makr furthest extent of the ice
-forms during a temporary halt in glaciers retreat, creating ridge behind terminal moraine
lateral moraines
-high and almost symmetrical ridges, formed along outer edge of glacier
-can be several metres high, formed from scree (crumbled rocks at bottom of mountain)
medial moraines
-when lateral moraines from 2 merging glaciers join up, leaving line of debris in centre of combined glacier flow
-as combined glaciers melt, medial moraine deposited to form low ridge
drumlins
-oval or egg shaped hill, made up of glacial till
-aligned in direction of ice flow
-vary in size, commonly 30-50m high, 500-1000km long
-occur usually in clusters or swarms on flat valley floors, or lowland plains in north england
till plain
extensive plain created by melting of a large ice sheet that detached from a glacier
-till effectively levels out the topography to create mostly flat landscape
-angular, unsorted till (rock debris deposited in situ), often divided into lodgement till (dropped by moving glaciers) and ablation till (dropped by stagnant or retreating glacier)
erratics
-a boulder or rock fragment deposited far from its origin
-erratics give clues to establish direction of previous ice movements and also help recreate paleo-envirwonments
-by workings out source of erratic, origin of ice can be established
