GLACIATION and Glacial Erosion 2014 (i).pdf · Hanging Valley . Sometimes smaller glaciers can form...

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.