Transcript Slide 1

7.1 GLACIERS
Root Words:
Col = together (collaborate)
Com = together (commune)
Cogn = know (cognizant)
Con = with (convention)
Contra = against (contradict)
Corp = body (corpse)
Cosm = universe (cosmonaut)
Counter = opposite (counteract)
Cranio = skull (cranium)
Cred = believe (credible)
15,000 years ago…
Ice Age People Constructed Mammoth-Bone
Shelters on the East European Plain
15,000 years ago…
Humans developed a relationship with dogs.
15,000 years ago…
Humans had travelled spread throughout
Europe, Africa and the Americas.
15,000 years ago…
The Earth was 30% covered in GLACIERS!
Glacier
French
Long
Fjords
Yosemite
Alps
Island
of Norway
Valley
Cape
Cod
All shaped by glaciers!
Great Lakes
GLACIER = thick mass of ice that forms over hundreds
or thousands of years.
ICE AGE = a period of time when much of Earth’s land is
covered by glaciers.
Flash: Earth’s Changing Climates
SNOWLINE = the lowest elevation in a particular area that
remains cover in snow all year.
Antarctica
snowline
Peru
Glaciers form when new snow falls onto old snow
year after year after year building up the snow.
As the newer snow piles up it exerts pressure on the
older snow causing it to recrystallize into coarse grains
of ice.
Valley Glacier = a stream
of ice that flows between
steep rock walls from a
place near the top of the
mountain valley.
Ice sheet = ice that covers a large region where the
climate is extremely cold.
Only two ice sheets remain now.
Antarctica
Nearly 2/3 of Earth’s Freshwater!
If the Antarctica ice melted,
it would raise seal level 60-70 meters!
Greenland
How Glaciers Move
PLASTIC FLOW = movement within the ice as the ice
distorts and changes shape.
Beginning at about 50
meters below the glacier
surface the weight of
overlying ice puts pressure
on ice below causing it to
flow.
Basal Slips = Gravity causes the entire ice mass to slip and
slide downhill along the ground.
Zone of Fracture = the brittle outermost
zone of the glacier. When the glacier flows
over uneven ground cracks called
CREVASSES form which can be up to 50
meters deep but snow cover the tops
making travel over glaciers very dangerous!
GLACIAL BUDGET = balance between accumulation of
snow/ice at the upper end of the glacier and loss/wastage
at the lower end.
Zone of Accumulation
Snowline
Crevasses
Zone of Wastage
Iceberg
Glacial Advance and Retreat
If more ice accumulates at the beginning of the glacier
than is lost at the end of the glacier, then the glacier
will advance.
Glacial Advance and Retreat
If more ice is lost a the end of the glacier than
accumulates at the beginning, then the glacier will
retreat.
Regardless if ice is
gained or lost, the
glacier still flows
downhill.
CALVING = when large chunks of ice break off the end
of an iceberg.
ICEBERG = very, very
large chunk of ice
that has calved from
an iceberg and is
floating in the
ocean.
Only about 10% is
visible above the
surface of the water.
LANDFORMS CREATED BY GLACIAL EROSION
Glaciated Valleys = valleys that are widened from their
original V-shape to a U-shape called a glacial TROUGH.
Hanging Valleys = valleys cut by smaller glaciers that
enter into a valley cut by a larger glacier.
Hanging valleys
are not cut as
deep so are left
standing higher
than the main
valley.
Pg. 193 Fig. 7
CIRQUE = bowl-shaped depression a the head of a glacial
valley that is surrounded on three sides by steep rock
walls.
Yosemite
HORN = sharp pyramid-like
peaks had cirques
surrounding them.
^ = snaking, sharpARETE
edged ridges where
cirques occur on
opposite sides of a
divide.
Matterhorn, Switzerland
GLACIAL DEPOSITION LANDFORMS
New England pasture (rocky) Midwest farmland (rolling)
Dakota wheat field
TYPES OF GLACIAL DRIFT
(All types of sediments of glacial origin.)
1. TILL = deposited directly by the glacier as it melts.
(typically contains many different sizes of particles)
2. Stratified Drift = sediment deposits that are sorts
according to particle size and weight.
Boulders deposited by glaciers can be identified because
they have a different composition (glacial erratics) to
that of the bedrock upon which they rest.
Glacial Erratics of New England
MORAINES = layers or ridges of till left by glaciers
1. Lateral Moraines = ridges that from along the sides of glacial
walls as the glacier gather debris from the walls of the valley.
2. End Moraines = deposit of till at the end of a glacier that has
been stationary for long periods of time. This till is carried from
the beginning of the glacier to the end of the glacier within the
glacier itself.
The Pas Moraine shows
a stagnant stage in the
retreat of the large ice
sheet. The fluted stripes
in the landscape (E)
show the direction of
the ice flow. The dark
ridge in the middle is
the end of the ice sheet
where glacial tills and
end moraine formed a
significant elevation in
the landscape.
3. Ground Moraines = glacial till that forms as a glacier begins
to recede usually creating a rocky plain. Often results in poorly
drained swamp lands.
5. Terminal Moraines = as a glacier recedes it leaves several end
moraines. The farthest end moraine is called the Terminal
Moraine.
6. Recessional Moraines = the end moraines that form all along as
the glacier melts are called recessional moraines.
(Page 197 Figure 12)
Terminal Moraine
Recessional Moraine
Outwash Plains = broad, ramp-like structure made as the glacial
milk washes out of the end moraine.
Kettle = depressions and small lakes within end moraines and
outwash plains that form when a block of glacial ice doesn’t
flow with the glacial milk and is buried then melts later.
Older kettle moraine; Walden Pond, MA
New kettle moraine, New Zealand
Rochester, NY
Drumlins = streamlined hills composed of till that are
taller and steeper at one end.
(Drumlin Fields = cluster of drumlins)
The steep side of the drumlin faces the direction the ice
came from and the other side faces where the ice went.
Esker = snake-like ridges that formed from streams that
flowed under glaciers.
Manitoba, CANADA
The Most Recent Ice Age…
began 2-3 million years ago.
Pg 198 Figure 13
Glacial Change
http://video.pbs.org/video
/994540147/chapter/1/sea
rch/glaciers
Alaska