Transcript Glaciation Review Powerpoint

GLACIERS
An agent of erosion, weathering, and deposition
What are glaciers?
• Glaciers are large masses of moving ice and
snow on land
• They are found in areas where there is a lot of
snowfall that doesn’t melt from winter to
winter
• As a result, a deep layer of compacted snow
accumulates. This layer of snow becomes
compressed into a thick sheet of ice.
What makes glaciers unique is that they move. Due
to their mass and the force of gravity, glaciers flow
down hill a few centimeters or meters per year.
These great sheets of ice -glaciers- create landforms
through both erosion and deposition.
How does a glacier work?
• As the glacier grows from ice accumulation, it
begins to melt on the bottom because of all
the pressure from above
• When it melts, it begins to slide, and the dirt
and rocks underneath the glacier erode the
surface that the glacier drags across
• Over time, rocks and sediments carried by
moving glaciers can carve or deepen valleys
In the photo above, you can see “scratches” on the
rock left by the action of a glacier.
Imagine that scrapping continuing for millions of
years and you can see how glaciers turn
V shaped valleys into U shaped valleys.
http://www.flickr.com/ theslowlane
As the glacier moves through a V-shaped valley,
it sculpts a “U”.
A horn is a
pyramid-shaped
mountain peak
created by
several glaciers
eroding away at
different sides of
the same
mountain.
http://www.geology.wisc.edu
How does a glacier work?
• Glaciers also deposit materials, as their front
end melt
• The glacier continues to move, but it melts
faster than it moves (retreating)
• As the ice melts, it drops its load (rocks,
sediment), far from where they originally were
Wikipedia Commons
Wikipedia Commons
Rocks and
.
sediment
deposited on
the sides or
the end of
glaciers
create
moraines, like
these.
There are two types of glaciers
Continental glaciers form over large areas of continents
close to the North and South Poles.
Continental glacier in Antarctica
Mountain glaciers are relatively small glaciers that
form near the tops of mountains.
Mountain glacier in the Rocky Mountains
During the past Ice
Ages, very thick
continental ice
sheets overlaid much
of the continent of
North America.
These very thick
glaciers covered all
but the highest
mountains and
resulted in significant
erosion.
Grey shaded area—continental glaciers
Many lakes in North America including the Great
Lakes, were created by glaciers moving over the
rock and gouging out deep “holes” which filled
with water when the glaciers melted.
In the last Ice Age, which ended approximately 10,000
years ago, 32% of Earth's land area was covered with
glaciers.
Glaciers now cover
only about 10% of
the land area.
That glacial ice is found mainly over Antarctica.
Most of the other glaciers cover Greenland; the
remaining small percentage are mountain glaciers
found in places such as Alaska, the Canadian
Arctic, New Zealand, the Himalayan Mountains,
the Rocky Mountains and the Alps.