• By the end of today's
lessons you will be able
to recognize Arêtes and
explain the formation of
glacial troughs and
hanging valleys.
• Key Words;
• Glaciated
trough
• Truncated
spur
• Hanging
valley
What’s this?
Formation of an arête
Arêtes are ‘knife-edged’ ridges formed between two corries.
Formation of a pyramidal peak
arête
tarn
Pyramidal peaks
are formed when
three or more
corries cut
backwards into the
same mountain.
corrie
Label the pyramidal peak diagram
1. Glaciers flowing out corries and moving
downhill follow the easiest route, in most
cases this is am existing river valley.
2. However glaciers often fill much of the
valley and have a much greater erosive
power.
3. Therefore instead of flowing around
obstacles, such as interlocking spurs the
glacier is able to widen, deepen and
straighten the valley.
4. The result is a U shaped cross section
known as a Glacial Trough.
Formation of a glacial trough
Characteristics of a glacial trough
What are the characteristics of a glacial trough?
steep valley sides
hanging valley
Between truncated
spurs are hanging
valleys which
have not been
eroded as deeply
as the main valley.
Interlocking spurs are
truncated as the
glacier cuts straight
through the landscape.
misfit stream
The river
that flows
through
the valley
after the
ice age is
described
as a
misfit
stream.
wide and flat valley floor
truncated spurs
1. As the glacier moves down the valley
it works like a giant bulldozer.
2. It wears away anything in its path and
smoothes the valley sides.
3. It removes the ends of interlocking
spurs to leave steep, cliff like,
Truncated Spurs.
4. Truncated Spurs are shortened or cut
off ridges caused by glacial erosion.
1.
2.
3.
4.
Hanging valleys are
formed as a result of
erosion in the main and
tributary valleys.
The floor of the tributary
valleys is eroded at a
slower rate than that of the
main valley.
When the ice melts the
tributary valley is left
hanging above the main
valley.
The stream in the hanging
valley will now fall as a
waterfall into the main
valley.
Hanging Valley
Nant Ffrancon Valley, Snowdonia
What evidence is there to suggest that this valley has
been shaped by ice?
Produce an annotated sketch to show that this is a
glaciated valley.
• Draw a before and
after diagram of a
glacial valley.
• Label the physical
landforms and
briefly explain their
formation.