GLACIATION

and Glacial

Erosion.

GlaciationGlaciation Video

Ice Caps – cover land less than

50,000sq kms

Ice Sheets – cover land more than

50,000 sq kms.

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

An ARETE is

a thin, knife

edged ridge

between

two corries.

When two corries

exist back to back,

the dividing wall

is eroded and so

becomes thinner.

This is called an

ARETE.

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

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

Greenland

Truncated spurs

create steep valley

sides

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.