Erosion and Deposition by Ice
Objectives
• Explain the difference between alpine
glaciers and continental glaciers.
• Describe two ways in which glaciers
move.
• Identify five landscape features
formed by alpine glaciers.
• Identify four types of moraines.
Glacier National Park
I. Glaciers: Rivers of Ice
A. A glacier is a large mass
of moving ice. They are
capable of eroding, moving,
and depositing large
amounts of rock materials.
B. Glaciers form in areas so
cold that snow stays on the
ground year-round.
Because glaciers are so
massive, the pull of gravity
causes them to flow slowly,
like “rivers of ice.”
Elephant Foot Glacier in Greenland
Glaciers
I. Glaciers: Rivers of Ice continued
C. Alpine Glaciers form in
mountainous areas. One
common type of alpine
glacier is a valley glacier.
D. Valley glaciers form in
valleys originally created
by stream erosion. As
these glaciers slowly flow
downhill, they widen and
straighten the valleys into
broad U shapes.
I. Glaciers: Rivers of Ice continued
E. Continental Glaciers are huge,
continuous masses of ice that
can spread across entire
continents.
F. The largest continental glacier
in the world covers almost all of
Antarctica. This ice sheet is
approximately one and a half
times the size of the United
States, and is more than 4,000 m
thick in some places.
Pine Island Glacier (Antarctica)
I. Glaciers: Rivers of Ice
continued
F. Glaciers on the Move When
enough ice builds up on a
slope, the ice begins to move
downhill. Thick glaciers move
faster than thin glaciers, and
the steeper the slope, the
faster the glaciers will move.
G. Glaciers move in two ways:
sliding and flowing. A glacier
slides when its weight causes
the ice at the bottom to melt.
A glacier flows as ice crystals
within the glacier slip over
each other.
I. Glaciers: Rivers of Ice continued
H. Glacier
movement is
affected by climate.
As the Earth cools,
glaciers grow.
About 10,000 years
ago, a continental
glacier covered
most of North
America.
II. Landforms Carved by Glaciers
A. Continental glaciers and
alpine glaciers produce
landscapes that are very
different from one another.
B. Continental glaciers
smooth the landscape by
scraping and eroding
features that existed before
the ice appeared.
C. Alpine glaciers carve out
large amounts of rock
material and create
spectacular landforms.
III. Types of Glacial Deposits
A. As a glacier melts, it drops all the material it is
carrying. Glacial drift is the general term used to
describe all material carried and deposited by
glaciers.
B. Glacial drift is divided into two main types, till
and stratified drift.
III. Types of Glacial Deposits continued
C. Till Deposits Unsorted rock
material that is deposited
directly by the ice when it
melts is called till. Unsorted
means that the till is made up
of rock material of different
sizes.
D. The most common till
deposits are moraines.
Moraines generally form
ridges along the edges of
glaciers.
III. Types of Glacial Deposits continued
E. Stratified drift is a glacial deposit that has been
sorted and layered by the action of streams or
meltwater.
F. Streams carry sorted material and deposit it in
front of the glacier in a broad area called an
outwash plain.
G. Sometimes, a block of ice is left in an outwash
plain when a glacier retreats. As the ice melts,
sediment builds up around the block of ice, forming
a depression called a kettle.