Geology Reference
In-Depth Information
Table 10.3 Landforms created by glacial deposition
Orientation with
ice flow
Landform
Description
Supraglacial (still accumulating)
Parallel
Lateral moraine
A moraine, often with an ice core, formed along the side of a valley glacier
Medial moraine
A moraine formed by the coalescence of two lateral moraines at a spur
between two valley glaciers
Transverse
Shear or thrust moraine Ridges of debris from the base of a glacier brought to the surface by
longitudinal compression
Rockfall
Rockslides from the valley-side slopes deposit lobes of angular debris across
a glacier
Non-orientated
Dirt cone
Cones of debris derived from pools in supraglacial streams
Erratic
A large, isolated angular block of rock carried by a glacier and deposited
far from its source
Crevasse fill
Debris washed into an originally clean crevasse by surface meltwater
streams
Supraglacial during deposition
Parallel
Lateral moraine
A moraine, often with an ice core, formed along the side of a valley glacier
(in part subglacial)
Moraine dump
A blanket of debris near the glacier snout where several medial moraines
merge
Non-orientated
Hummocky (or dead
ice/disintegration)
moraine
A seemingly random assemblage of hummocks, knobs, and ridges
(composed of till and ill-sorted clastic sediments) that contains kettles,
depressions, and basins
Erratic
A large rock fragment (clast) transported by ice action and of different
composition from the local rocks
Subglacial during deposition
Parallel
Drumlin
An elongated hill with an oval, egg-shaped, or cigar-shaped outline
Drumlinoid ridge
(drumlinized
ground moraine)
Elongated, cigar-shaped ridges, and spindle forms. Formed under ice in
conditions unsuited to individual drumlin formation
Fluted moraine (flute)
Large furrows, up to about2minwavelength, resembling a ploughed field.
Found on fresh lodgement till (till laid in ground moraine under the ice)
surfaces and, occasionally, glaciofluvial sand and gravel
Crag-and-tail ridge
A tail of glacial sediments in the lee of a rock obstruction
Transverse
De Geer (washboard)
moraine
A series of small, roughly parallel ridges of till lying across the direction of
ice advance. Often associated with lakes or former lakes
Rogen (ribbed,
cross-valley)
moraine
A crescentic landform composed chiefly of till, orientated with its long axis
normal to ice flow and its horns pointing in the down-ice direction
Non-orientated Ground moraine:
A blanket of mixed glacial sediments (primarily tills and other diamictons),
characteristically of low relief
Till plain
Almost flat, slightly rolling, gently sloping plains comprising a thick blanket
of till
Continued
