17 Flashcards
Glacier
An accumulation of snow and
ice, that lasts year round.
Thick enough to flow downhill
under its own weight.
Categories of Glaciers
Mountain glaciers
Continental glaciers (Greenland, Ant Artica)
Mountain Glaciers - Cirque
Fill mountaintop bowls.
Mountain Glaciers - Valley
Low like rivers down valleys.
Mountain Glaciers - Ice caps
Covers peaks and ridges.
Mountain Glaciers - Piedmont
Spread out at the end of a valley.
Continental Glaciers
Vast ice sheets covering large
land areas.
Ice flows outward from thickest
part of sheet.
Basal slip
Forming or belonging to
a bottom layer.
Significant quantities of
meltwater forms at glacier base.
Plastic Deformation
Crevasses form at surface—upper zone is stretching.
Not reversable.
Zone of accumulation
Area of net snow addition.
Zone of ablation
Area of net ice loss.
Toe
The leading edge of a glacier.
Glaciers are important forces of
landscape change…
…Erosion, transport, deposition
Tarn
A lake inside a cirque.
Arete
Knife-edge ridge.
Two cirques or two
valley glaciers that have eroded
toward one another.
Glaciers act as…
…large-scale conveyor belts.
Sediment transport is always…
… in one direction (downhill).
Debris at the toe of a glacier is called…
…end moraine.
Moraines
Unsorted debris deposited by a
glacier.
(Moraines) Lateral
Forms along the flank of a
valley glacier.
(Moraines) Lateral
Forms along the flank of a valley glacier.
(Moraines) Medial
Mid-ice moraine from
merging of lateral moraines.
Glacial Till
Sediment dropped by glacial ice.
Erractics
Boulders dropped by glacial ice
Different from the underlying bedrock
Carried long distances in ice.
Loess
Wind-transported silt.
Glaciers produce abundant amounts of fine sediment.
Strong winds over ice blow the rock flour away.
Terminal moraines
Form at the farthest
edge of flow.
End Moraines
Form at the stable toe of
a glacier.
Ground Moraine
Till left behind by rapid ice
retreat.
Creates a hummocky (irregular)
surface.
Kettle lakes form from stranded
ice blocks.
Drumlins
Long, aligned hills of molded till.
◦ Asymmetric form—steep up-ice; tapered down-ice.
◦ Commonly occur as swarms aligned parallel to ice-flow direction.
◦ Basic theory – till is dropped below glacier and as it moves over, shapes it into the shape of a teardrop.
Eskers
Long, sinuous ridges of sand and gravel.
Th
ey form as meltwater channels within or below ice.
Channel sediment is released
when the ice melts.
Consequences of Continental Glaciation
Ice loading and glacial rebound
◦ Ice sheets depress the lithosphere into the mantle.
◦ Slow crustal subsidence follows flow of asthenosphere.
◦ After ice melts, the depressed
lithosphere rebounds.
◦ The last ice-age glacial rebound continues slowly today.
Glacial Consequences
Sea level—ice ages cause sea level to rise and fall
◦ Water stored on land during an ice age: sea level falls.
◦ Deglaciation returns water to oceans: sea level rises
◦ Sea level was ~100 m lower during the last ice age.
◦ If ice sheets melted, coastal regions would be flooded.
Pleistocene Ice Ages
All climate and vegetation belts were shifted southward.
