The Work of Ice
Read pages 233-242
Define the following:
1. continental glaciation- glaciers that covers a large part of a continent,
for example Greenland
2. alpine glaciation- glaciers or ice sheets that occur in mountainous
regions, for example the mountainous regions of B.C.
3. ice age- the period in which temperatures plunged and large parts of
the earth’s surface were covered in glacial ice
4. interglacial period- periods in time in which a distinct period of
warmer conditions between glacial periods when the earth’s glaciers
have retreated or shrunk
5. snow line- the level of altitude above which snow exists on a
permanent basis
6. firn- glacial snow
7. basal slippage- the advance of a glacier by slow movement along the
valley floor; occurs in warm glaciers where the ice is at its melting
point
8. snout- the foremost extent of a glacier
9. isostasy- the theory that account for the upward movement of
mountains
Questions
1. What causes glaciers to advance? The most significant property of
glacial ice is that it flows like a thick liquid. The immense pressure of
its own mass causes the ice to flow outward from its source.
2. Draw Fig. 32.2 and 32.3
3. In what ways can ice be compared to sedimentary rock?
Like sedimentary rock, glacial ice develops in layers as fresh
accumulations of snow are added each winter. Deep beneath the
surface the layers of ice are changing. Air pockets between the ice
crystals are squeezed out. The ice crystals then grow and join
together to form a solid sheet of ice. Essentially they change because
of the great pressure of the ice above. This change can take a long
time. In Antarctica, it may take 1000 years for surface snow to
change into glacial ice.
4. Why are there still continental glaciers in the Antarctic and
Greenland?
Temperatures are so high at lower elevations that glaciers don’t form.
Glaciers form in mountains where temperatures are lower,
See back for final question!
5. Complete the following chart comparing features formed by
continental and alpine glaciation:
Continental Glaciers
Alpine Glaciers
Erosion
Erosion
Finger lakes- when glaciers
retreated, many hollows were filled
with water- Great Lakes
Cirques- circular hollow with steep
sides cut into bedrock
Isostasy- similar to erosion in that
massive pressure of glacial ice
forced the surface to be lowered(
but when the glacier is gone the
crust rebounds)
Depositional
Moraines- hill of unsorted drift that
accumulates along the edges of a
glacier
Kames- hill resulting around kettles
where ice has not been buried under
drift
Drumlins- streamlined cigar shaped
hill formed parallel to the direction
of glacial flow around an immovable
block of bedrock
Eskers- thin meandering hills
deposited by streams flowing
through, under, or on top of the
Arête- formed when two cirques are
close to each other forming a
chiseled ridge
Hanging valleys- - are formed when
tributary glaciers flow into main
glaciers
Fjords- u-shaped valleys that are
flooded by seawater when the
glaciers melt
Depositional features (similar to
continental glaciation)
Lateral moraines- form along the
sides of glaciers as it flows through
a mountain valley.
Medial moraine- when two glaciers
come together, they remain
separate, flowing along side by side.
The ridge of till formed between
them is a medial moraine.
glacier
Outwash fan- delta formed from
glacial meltwater
Skerries- terminal moraines formed
in fjords. Often these are
submerged, but sometimes they
emerge to form islands at the
mouths of fjords.