Transcript Glacial Deposits (continued)

Glaciers
Landmarks of the Past
• Glaciers: Large mass of ice, air, rock
debris.
– At least partially formed on land
– Constantly moving
– Permanent
• Glaciation: Formation, activity, and retreat
of glaciers
• Firn: Snow that has survived the summer,
first step to becoming glacial ice.
• Pressure compacts snow and makes it into
glacial ice
• Types of glaciers are:
– Valley/Alpine: glacier formed from a cirque (bowl shaped
depression in a mountain) and spread into a valley
– Piedmont:
valley glacier
that extends
beyond the
mountain
– Ice Cap: covers mountain top and spreads radially
– Continental/Polar: glacier formed at the poles
– Ice sheet: Large sheet of ice that covers earths
topography
Glacier Formation
• Accumulation: adding of materials to
glacier
• Ablation- removing of materials from a
glacier
• Equilibrium line: where accumulation
zone and ablation zone meet
Glacial Drift
• Glacial Drift: Movement of glacier
(easiest path)
• Pressure: Force that drives glacial
movement
• Ductile: Can be reshaped (ex. silly puddy)
• Basal Sliding: Sliding of glacier on super
cooled water
• Ice Stream: fast moving part of a glacier
½ mile/yr
Glacial Striations
• Glacial
Striations:
Scratches in
rocks made by
glaciers
dragging other
smaller rocks
over the striated
rock
Glacial Deposition
• Deposition: Dropping of materials by
glaciers
• Glacial Till: Material dropped by glaciers
made of:
– Rock Flour: Finely ground rock powders
– Erratics: Large rocks or boulders carried away
from their place of origin
• Beautiful turquoise lake near valley glaciers in Alberta, Canada.
Meltwater streams carry rock flour into the lake. The color of the lake is
caused by all the very fine sediment suspended in the water.
Glacial Erratics
Types of Glacial Depositions
• Moraines: Depositions left on the outsides
of glaciers
• Types of Morains
– Lateral: side of glaciers
– Medial: between two glaciers
– Terminal: end of glacier
• Convergent Ice flow: 2 glaciers meet and
flow together as 1
• Divergent Ice Flow: 1 glacier separates
into 2 different glaciers
Moraines
Glacial Deposition (continued)
• Kame: Hill or mound of glacial till and ice that
broke off of glacier
• Kettle: Bowl shaped depression found after
glacial ice is broken off, covered with till, and
compresses the earth.
• Kettle lake: Kettle that has collapsed filled and
with water
• Pothole lake: Lake that forms at a terminal
moraine or by a Kame
• Drumlin: Sediment filled depressions
Glacial Deposits (continued)
• Outwash: Water that rushes out from under
or above a melting glacier
• Esker
• Braided Stream
• Delta: Deposition of sediment at mouth of
a stream
Esker
• Esker: Long narrow
ridge of glacial debris
that was left behind by
an outwash that
flowed under the
glacier.
Esker
Braided Stream
• Braided Stream:
Streams formed in
glacial till that has a
braided and irregular
appearance
Delta
Delta and Braided Streams
Calving and Abduction Zone
Sea Ice Formation
• Frazil Ice (1)
– Slushy salt
water. First
step to
becoming
Sea Ice
• Grease Ice (2)
– Forms when Frazil Ice begins to congeal
forming a thin “greasy” layer on top of it.
• Pancake Ice (3)
– 3rd step in Sea Ice formation. Grease Ice
sticks together forming small “pancakes”.
• Sea Ice (4)
– Frozen Salt
Water. May
or may not
be attached
to land.
Ice Shelf
Larsen B
Ice Shelf
(Antarctica)