Page 283 - Fundamentals of Geomorphology

266 PROCESS AND FORM

completely or largely homogenized by shearing sedi- Other ice-marginal landforms, which have no pre-
ment that is laid down by a glacier sole while sliding ferred orientation with respect to ice flow, are hummocky
over or deforming its bed (or both). moraine and various forms resulting from mass move-
3 Melt-out till – sediment released by the melting of ments (rockfalls, slumps, and debris flows). A hummocky
stagnant or slowly moving debris-rich glacier ice, moraine formed near the ice margin is similar to a
and directly deposited without later transport or hummocky moraine produced elsewhere, but it includes
deformation. irregular heaps of debris that fall from an ice mass in the
ice-marginal zone and debris from dead ice that becomes
detached from the main ice mass.
Ice-margin landforms
Landforms produced at the ice margin include differ-
ent types of end moraine, all of which form around a
glacier snout. A lateral moraine lies at the sides of a glacier GLACIOFLUVIAL LANDFORMS
(Plate 10.12). A terminal moraine is an arcuate end
moraine that forms around the lobe of a glacier at its far- Huge quantities of sediment are shifted by meltwa-
thest limit (Plate 10.13; Colour Plate 12). A recessional ter. Indeed, more sediment may leave a glacial system
moraine marks a time of temporary halt to glacial retreat in meltwater than in ice. Sediment-charged meltwa-
and is not currently touching a glacier. A push moraine ter under a glacier is a potent erosive agent, especially
is formed by sediment being bulldozed by a glacier towards the glacier snout. After leaving a glacier, meltwa-
snout, especially a cold glacier. Some push moraines show ter may erode sediments, as well as laying down debris to
annual cycles of formation and comprise a set of small, createice-marginalandproglacialdepositionallandforms
closely spaced ridges. (Table 10.4).

Plate 10.12 A pair of lateral moraines from a valley glacier in the Cordillera Blanca, Peru. Former ice flow is towards
the viewer.
(Photograph by Neil Glasser)