GLACIATION
and Glacial
Erosion
Ice Caps – cover land less than
50,000sq kms
Ice Sheets – cover land more than 50,000
sq kms.
Shrinking of Greenland Ice
sheet.
Glaciers are rivers of ice that flow from mountainous areas onto
the lowlands
Ice can be
hundreds of metres
thick
The ice carries soil and
boulders with it.
Crevasses exist in
the ice – this is
evidence that the
ice is moving
Large boulders can be
carried by the ice and
deposited hundreds of
kms from where they
originated
When the ice melts these
boulders, called erratics, can
be left in strange places
CORRIES,
CIRQUES
Ice and snow can
collect in a hollow
in the side of a
mountain
Eventually the hollow becomes too small for all
the snow and so it spills out and makes its way
down the mountainside
When the ice melts, a deep hollow is left in
the side of the mountain. This is a corrie or
a cirque. Sometimes it may contain water
ARETES
When two corries
exist back to back,
the dividing wall
is eroded and so
becomes thinner.
This is called an
ARETE.
An ARETE is
a thin, knife
edged ridge
between two
corries.
PYRAMIDAL
PEAK
When a mountain peak contains TWO or
more aretes, it takes on the shape of a
triangle and is called a PYRAMIDAL peak
The Matterhorn in the Alps is the best example
U SHAPED
VALLEYS
When the
ice flows
out of the
corrie it
makes its
way down
onto the
lowlands in
a glacier.
Glaciers usually make their way down old
river valleys. Due to the strength of the
glacier it is eroding the bed and the sides of
the river valley as it moves.
When the ice
melts, a U
shaped valley
is formed.
This has
steep sides
and a flat
floor
Ribbon
lakes
Steep
sides
Glendalough
Ribbon
lakes
Flat
floored
valley
Steep sides of U
shaped valley
Hanging
Valley
Sometimes
smaller
glaciers can
form high
up in the
mountains
at right
angles to the
main glacier
Because they
are not as
powerful,
they do not
erode as
much
When the
ice melts, the
smaller
valley is left
above the
main valley.
This is
called a
HANGING
valley
Very often a
waterfall flows
from the
hanging valley
down into the
main U shaped
valley.
TRUNCATED
SPURS
Greenland
Truncated spurs create
steep valley sides
As the ice makes its
may through the V
shaped valley, it
bulldozes through the
interlocking spurs
originally formed by
the stream. As a result
the valley now takes
on a steep sided
shape. The sides are
now called
TRUNCATED
SPURS
RIBBON
LAKES
As the glacier makes
its way down
through the u shaped
valley, it meets
sections of rock on
the valley floor. It
freezes around them
and so when it moves
plucks out the rock
and carries it with it.
The hollow left on
the valley floor can
fill with water to be
called a RIBBON
LAKE
These ribbon
lakes can also
be called
PATER
NOSTER
lakes as they
are thought to
resemble the
beads on a
Rosary beads
There is no
limit to the
amount of
lakes that
can be
found in
the U
shaped
valley.
Ribbon
lakes can
be any
size or
shape
FIORD,
FJORD
Sometimes the glacier can move out to sea and cut a U
shaped valley that ends at the coastline. When the ice
melts, the section of the u shaped valley closest to the
coast can flood and so it is called a FIORD
Killary Harbour, Ireland’s only FIORD
FIORD Norway
FIORD NORWAY
Landscape
features in
West of
Ireland
formed by
glaciers.