Transcript Land Modifying Processes

SIHC - Glaciation
Glaciation
Erosion by bodies
of moving ice.
 Erosion processes are very active in the SIHC
because of climate.
 The cold temperatures, due to high altitude,
have meant that glaciation is an important
land modifying process.
Formation of Glaciers
 Over time snow turns to glacial ice high in the
mountains.
 It is formed in three major steps.
 Glaciers move due to the structure of the
crystals, melt water and the pull of gravity.
 There are two major zones within the glacial
system: accumulation and ablation.
 Moraine often covers the lower extent of
glaciers.
Hooker Glacier
Glacial ice is formed in three major steps.
 Feathery snowflakes - Snow falls high in the
mountains and collects in neve as white powder. As
more snow is added the structure of the snow alters.
 Firn or "old snow" - The pressure applied from the
weight of snow above bears down on the snow below
compacting and pressing the air out. Larger ice
crystals form. These crystals are called firn or "old
snow".
 Glacial ice - Over time as the depth of snow increases
and the firn is buried more deeply. Now more air is
forced out until the ice crystals are completely
compacted forming clear blue glacial ice.
Neve
How do glaciers move?
 When the ice becomes thick enough to flow, about
50m, the glacier will begin to move away from its
source.
 At this depth the ice creates enough pressure to allow
the lowest ice to undergo plastic deformation, ie: it
begins to flow like a soft or liquid plastic.
 Glaciers also have a thin film of water underneath and
at the side, which helps the movement down the
valley by the pull of gravity.
 The glacier will advance along the valley, remain
stationary or retreat depending on the balance
between the amount of new ice collected in the source
area and the rate of ablation in the rest of the glacier.
 The velocity of ice flow in all glaciers varies
considerably from a few metres over a period
of years to several metres per day.
 The rate depends on such factors as the
thickness of the ice, the slope of the surface
over which the glacier is advancing, and the
amount of meltwater that is available to
lubricate the base of the glacier.
A glacial formation
Within the glacial system there are two
major zones
 Accumulation zone
This is near the top of the glacier where snow and ice
are added. This zone comprises mostly snowflakes,
firn and glacial ice.
 Ablation zone
Found towards the terminal end of the glacier where
ice melts away.
 Old glacial ice is exposed with many crevasses. This
zone comprises mostly glacial ice, water and
accumulations of moraine.
 Between these zones is the equilibrium line. This is the
balance point between the accumulation and ablation
zones. No ice mass is lost or gained at this point.
Erosion by Glaciers
 The ice in glaciers causes a lot of erosion in
alpine regions of the world.
 As glacial ice forms it presses on the sides of
the valley.
 It makes a bowl shaped basin at the top of
the mountain called a cirque.
 Water around the glacier and gravity help it
slide down the valley.
Abrasion by a glacier
 Glaciers scrape the walls and floor of the
valleys as they slide down.
 This is called glacial abrasion.
 The glacier has many rocks and boulders in
the ice.
 The glacier acts like a huge belt sander
eroding tonnes and tonnes of rock as it slides
down the mountains.
Abrasion
 The millions of tonnes of rock come from the
valley floor and walls. Other rocks fall on to the
top of the glacier as it goes by. Some of these
rocks fall into the glacier through crevasses.
Glaciers carry tiny bits of rock as well as huge
boulders. The tiny rock particles are called rock
flour.
 All the rock around and on a glacier is called
moraine. A glacier is like a bulldozer and pushes
the moraine along in front of it. Other rocks are
left at the side and the streams under the glacier
carry some away.
Hooker Glacier
Moraine
 All the rocks in, on and around a glacier are called
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moraine. These rocks move along with the glacier.
Moraine has different names when it is on
different parts of a glacier.
Lateral moraine is at the sides of a glacier
Medial moraine is on top of the glacier
Terminal moraine is at the end of the glacier
Piles of moraine are left when a glacier melts.
These moraine walls show how far a glacier has
been down a valley.
Tasman Glacier
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The Glacial System at Franz Josef and Fox
 Inputs:
 Processes: name types of
 Outputs: describe the
Climate_________________
Orogeny________________
Altitude_________________
Relief_________________
Gravity ________________
Erosion________________, _________, ____________
Transportation__________, _________, _____________
Deposition______________, ___________, ___________
Natural features
______________
______________
______________
______________
______________
______________
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