2. 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
3. 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
5. 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 TOP
WITHIN
UNDERNEATH
6. 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
8. 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 Whangaehu
glaciation freeze-thaw small
two cirques centimetres
U terminal winter
summer plucks moraine
100,000 Proto-Ngaruhoe cinder
Mangatepopo resistant Ruapehu
accumulates
9. The Work of Ice
The 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.
