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51 terms

Chapter 14

Glaciers and Glaciation
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Basal Slip
__________ is one of the two, major flow mechanisms in a glacier.
The [Milankovitch Theory] explains [cyclical] variations in Earth's [climate] as a result of variations in Earth's rotation and orbit.
The [-----] explains [-----] variations in Earth's [-----] as a result of variations in Earth's rotation and orbit.
True
Arête, horns and U-shaped valleys are erosional features carved from bedrock by glaciers.
Accumulation exceeds wastage
Which one of the following applies to a valley glacier that lengthens (extends its terminus downslope) over a period of many years?
U
A _____ cross-valley profile is typical of canyons and valleys eroded and deepended by alpine or valley glaciers.
hanging
Bridal Veil Falls in Yosemite National Park is an example of a 1.----- valley.
True
Till is an unsorted sediment deposited directly from the melting glacial ice; stream action is not involved.
Smooth, tapering ridge of till; formed and shaped beneath a continental ice sheet
A drumlin is a ____________.
cirque, tan
.----- basin in high, mountainous terrain can often be associated with a body of water called a 2.----- lake.
Terminal Moraine
Deposits of till at the terminus (front) of the glacier
Medial Moraine
Formed by the merging of two lateral moraines at a junction of two valley glaciers.
Lateral Moraine
Ridge of sediment deposited along margin of valley glacier
Kettle
Depressions from a retreating glacier that leaves a large block of ice that subsequently melts.
Valley Trains
Long, narrow deposit of stratified drift from braided melt water streams.
Kames
Conical hills of stratified drift; Originally deposited in a depression on glacier's surface.
glacier
Mass of ice that moves by plastic flow and basal slip
alpine glaciers
Confined to mountain valleys
Flow from high to low elevations
-Can be several kilometers across, 200 km long, and hundreds of meters thick
continental glaciers
vast ,Cover at least 50,000 km2
Also called ice sheets
ice caps
50,000 km2
-Mini ice sheets!
plastic flow
Stress and strain induce permanent deformation and movement
▪Occurs continuously
basal slip
Sliding over the underlying surface
▪Occurs occasionally
firn
Granular type of snow
is compacted and recrystallized to glacial ice
Glacial budget
Balance between expansion and contraction of glacier in response to accumulation and wastage
Zone of accumulation
Where additions exceed losses and surface always covered with snow
Zone of Ablation (Wastage)
Losses exceed additions, from melting, sublimation, calving
Firn limit
Separates zone of accumulation from zone of ablation
▪If moves up the glacier, the glacier is receding
▪If moves down the glacier, the glacier is advancing
plucking
Glacial ice pulls rock from bedrock
Bedrock eroded through abrasion:
Glacial polish
▪Smooth surface
Glacial striations
▪Scratches
Glacial flour
▪Pulverized rocks
Fiords
Glacial troughs full of water
-Usually along seacoast
Hanging Valleys
Tributary valley whose floor is above the main valley
-Often have spectacular waterfalls
-Nevada Falls,Yosemite
Arete
Narrow serrated ridge between two glacial valleys or cirques
-From headward erosion
Horn
Steep-walled pyramid-shaped peak formed by headward erosion of at least three cirques
Till
All sediment deposited by glaciers
Glacial erratics
Rock frags carried from source by glaciers
Stratified drift
Layered, with some sorting
Moraines
Layers or ridges of till
Types produced by alpine glaciers
Lateral Moraine
Medial Moraine
cirque
steep sided, half bowl shaped recess at the head of the glacier
glacial drift
the rock material carried and deposited by glaciers
abrasion
the process whereby rock is worn smooth by the impact of sediment transported by the movement of sediment-laden ice over bedrock
glacial polish
a smooth, glistening rock surface formed by the movement of sediment-laden ice over bedrock
glacial striation
scratch left in the ground by rocks carried by a glacier
end moraine
a ridge/mound of till that forms at the terminus (end) of a glacier
ground moraine
Layer of sediment released from melting ice as a glacier's terminus retreats
lateral moraine
Ridge of sediment deposited along margin of valley glacier
medial moraine
Moraine carried on central surface of glacier
-Formed when two lateral moraines merge
kettles
Depressions from a retreating glacier that leaves a large block of ice that subsequently melts
Drumlins
Elongated hills of till; often in extensive drumlin fields
Outwash plains
Sediment deposited by melt water from glacial terminus
Kames
Conical hills of stratified drift
Originally deposited in a depression on glacier's surface
eskers
Long, sinuous ridge of stratified drift
Deposited by running water in a tunnel beneath stagnant ice