Fluvioglacial Processes Fluvioglacial Processes and Landformsand Landforms

Features of lowland glaciationFeatures of lowland glaciation

Area of fluvio-glacial Area of fluvio-glacial landformslandforms

Subglacial streamSubglacial streamA stream that flows beneath a glacier, and which usually cuts into the ice above to form a tunnel.

Large subglacial stream channel that formed beneath the glacier Pastaruri, Peru when an ice-dammed lake drained.

Fluvioglacial landforms are created by the meltwater from glaciers, largely through deposition but also by erosion.

Glacier milkGlacier milk

Meltwater from a glacier, which commonly has a milky appearance from suspended fine sediment.

Meltwater from Vadret da Morteratsch, Grisons, Switzerland.

Photo taken on a July morning

Photo taken in the afternoon after ablation and subsequent runoff had both increased considerably

Braided streamBraided stream A relatively shallow stream with many branches that commonly recombine and migrate across a valley floor. Braided streams typically form downstream of a glacier.

Tasman River, South Island, New Zealand, fed by Tasman Glacier off the picture to the right, and the Hooker and Mueller glaciers in the valley in the centre background.

Esker A long, commonly sinuous ridge of sand and gravel, deposited by a stream in a subglacial tunnel.

Esker (arrowed) in NW Spitsbergen. The ridge is about 3 m high

Kame terraceKame terrace Valley-side terrace or bench formed by the deposition of fluvial sediment along the margin of a glacier. The terrace is left stranded on the hillside after the glacier has receded.

Kame terrace

KettleKettle (red arrows) (or kettleholekettlehole) A self-contained bowl-shaped depression within an area covered by glacial stream deposits, often containing a pond. A kettle forms from the burial of a mass of glacier ice by glacial or stream sediment, followed by its subsequent melting.

Kettles in the forefield of Glacier du Mont Miné, Valais, Switzerland.

Outwash plainOutwash plain (aerial view) A relatively flat spread of debris deposited by meltwater streams emanating from a glacier

Outwash plain in front of Thompson Glacier, Axel Heiberg Island, Canadian Arctic

Outwash plainOutwash plain (ground view) A relatively flat spread of debris deposited by meltwater streams emanating from a glacier.

Glaciologist crossing an outwash plain in front of Midre Lovénbreen in NW Spitsbergen, Svalbard

Proglacial lake Proglacial lake A lake developed immediately in front of the glacier, commonly bordered by the mounds of unconsolidated deposits that characterise the terminal zone of a glacier.

Proglacial lake at Sheridan Glacier near Cordova, Alaska.

VarvesVarvesA varve is a distinct layer of silt lying on top of a A varve is a distinct layer of silt lying on top of a layer of sand, deposited annually in lakes found layer of sand, deposited annually in lakes found near to glacial marginsnear to glacial margins

The coarser, lighter coloured sand is deposited during late spring when meltwater streams have their peak discharge and are carrying their maximum load.

As discharge decreases towards autumn when temperatures begin to drop, the finer, darker silt will settle.

Summary diagram – features produced by glaciation