Fluvioglacial Processes - ASGeography

Transcription

Fluvioglacial Processes - ASGeography
Fluvioglacial Processes
and Landforms
Features of lowland glaciation
Area of fluvio-glacial landforms
Fluvioglacial landforms are created by
the meltwater from glaciers, largely
through deposition but also by erosion.
Subglacial stream
A 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 icedammed lake drained.
Glacier milk
Meltwater from a
glacier, which
commonly has a
milky appearance
from suspended
fine sediment.
Photo
taken on a
July
morning
Photo taken in
the afternoon
after ablation
and
subsequent
runoff had
both increased
considerably
Meltwater from Vadret da Morteratsch, Grisons, Switzerland.
Braided 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 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
Kettle (red arrows) (or kettlehole) A self-contained bowlshaped 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 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 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
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.
Varves
A varve is a distinct layer of silt lying on top of a layer of
sand, deposited annually in lakes found near to glacial
margins
As discharge
decreases towards
autumn when
temperatures begin
to drop, the finer,
darker silt will
settle.
The coarser, lighter coloured sand is
deposited during late spring when
meltwater streams have their peak
discharge and are carrying their
maximum load.
Summary
diagram –
features
produced by
glaciation

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