GLACIAL PROCESSES

AIM• Explain how glaciers erode, transport and

deposit to create landforms in the TVC

Glaciers• A glacier is very slow moving

river of ice• Meltwater (underneath the

frozen ice) allows the glacier to slide over the ground and then move downhill due to gravity

• A top of a glacier looks cracked, theses are called crevasses.

• These cracks are formed due to the stress as the ice is pulled and moves at different speeds

Glaciers ERODE• A glacier erodes the valley floor and sides by plucking

and abrasion

PLUCKING ice touching the sides and ground can thaw slightly and then refreeze around rocks sticking out. When the glacier

moves forward, it plucks these rocks away

ABRASION debris carried in the glacier can scrape material off the valley walls and floor

Glaciers ERODE

Glaciers TRANSPORT• A glacier carries debris that is has plucked away or

bits of rock that have been broken off, or fallen onto the glacier.

• A glacier transports this debris in 3 ways

ON TOPWITHINUNDERNEATH

Glaciers DEPOSIT• A glacier deposit their load as they move and melt

LATERAL MORAINE is deposited where the sides of the glacier were

MEDIAL MORAINE is deposited in the centre of valley where 2 glaciers meet

TERMINAL MORAINE is deposited at the end of the glacier

Parts of a Glacier

The Work of Ice• Glue in the sheet labelled – The Work of Ice.• Fill in the gaps on the sheet, using the words below

Whakapapa moraine Whangaehuglaciation freeze-thaw smalltwo cirques centimetresU terminal wintersummer plucks moraine100,000 Proto-Ngaruhoe cinderMangatepopo resistant Ruapehuaccumulates

The Work of IceThe action of ice is known as glaciation. Glaciers begin in hollows known as cirques. Here the ice accumulates (gathers) and begins to flow. As it flows, the ice plucks rocks from the valley sides and floor. The action of freeze-thaw also produces small fragments which fall onto the glacier. These fragments carried by the glacier are called moraine.

A valley that is carved by a glacier has a characteristic u-shape . The glacier flows at a rate of a few centimetres a year. This tends to advance during winter and retreat during summer. A retreating glacier will dump the debris it is carrying to form a terminal moraine.

In the TVC there are two glaciers both on top of Mt Ruapehu. They are called the Whangaehu and Whakapapa glaciers. Both of these are very small in scale.

In the past however ice action was much more significant. During the ice ages, approx. 100,000 years ago huge glaciers carve the main volcano in the region known as Proto-Ngauruhoe. This covered most of the mountain and carved huge valleys into the soft cinder cone. An example of a valley formed this way is Mangatepopo. Only areas of hard resistant lava were not destroyed by the ice.