Glaciers Flashcards

Terms Definitions
Arrête
Sharp knife-edge ridge
 
 
 
Terminal(End) Moraine
 
 
 
 
End of Glacier
Crevasse
Open crack in the ice
Till
Unsorted material deposited directly from melting glaciers
Aretes
Oft-jagged ridge between adjacent glacial valley/troughs
Cirque/Corrie
Land scooped out from sliding glaciers
Drift
General term for all glacial deposits
Cirques
Broad amphitheaters hollowed out at head of glacial valleys
 

GLACIAL EROSION



 Glaciers erode large quantities of detritus and sculpt the landscape. Ice is very powerful.




• Amount of erosion depends on rate of glacial movement

• Thickness of ice
• Amount of rock fragments carried in ice
• Erodibility of rock surface
• Erosional processes
 
• Plucking
• Abrasion
• These processes produce
• Rock flour - pulverized rock
• Glacial striations - parallel grooves in rock
Outwash
Melting water that flows down the glacier
Pluvial Lake
A lake that experiences significant increase in depth and extent as a result of increased precipitation and reduced evaporation
Recessional Moraine
Ridges left at temporary glacial stands as part of an overall glacial retreat
Glacial Striations
Scratches in bedrock caused by dragging of stones in base of glaciers
Tarns
Small mountain lakes that occupy the basins of cirgues
 
 
 
 
Zone of Accumulation
 


addition of ice and snow
 
 
 
Continental Glacier
 
Continental Glacier - glacier that spreads out from a central mass of ice.

Found today in Greenland and Antarctica


Greenland: up to 3000m thick, 1.7 million sq. km


Antarctica: up to 4000m thick, 15.5 million sq km


North America was covered by ice sheet in Pleistocene
Tarn
A lake at high altitude formed from melting snow/ice
Kames
Deposit on a glacial surface that is lowered to the ground by glacial melting beneath it; usually appears as a small hill in a landscape
Ground Moraine
Relatively thin sheet of mainly till left by a rapidly retreating glacier
Zone of Ablation
Area where annual melting exceeds snowfall
Eskers
Ridges of sand & gravel deposited by glacial melt water in sub glacial tunnels; usually appear as winding ridges in the landscape
Isostatic Rebound
Rebound of land surface as & after glaciers melt away
 
 
Features Created by
erosion of Valley Glaciers

 U shaped valleys – Glacial Valley



Hanging valleys – Secondary glacial valley



Paster noster lakes – Series of connected glacial lakes



Fjords – Flooded glacial Valley


Aretes – Ridge that separates two glaciers


Horns – Peak between two or more glaciers


Cirque – Bowl shaped valley at head of glacial valley



Tarn – Lake remaining at head of glacial valley


Roches Moutonnees – (rock sheep) landscape due to rock plucking
Patternoster Lakes
A chain of lakes linked by a stream in a formerly glaciated valley
Snowflakes
Ice crystals.
CIRQUE
steep-sided, half-bowl shaped depressions carved into amountain at the
head of a glacier
Glaciers can calve underwater. T/F?
True!
movement
Rates of glacial movement
Average velocities vary considerably from one glacier to another
Rates of up to several meters per day
Some glaciers exhibit extremely rapid movements called surges
firn
intermediate form between snow and ice
Drumlins
elongated hills formed when a glacier overrides a glacial till
Terminus
Marks the farthest down valley extent of a glacier.
FIORD
coastal inlet that is a drowned glacially carved valley
calving
the process that causes glaciers to break up in ice bergs
Continental Glacier
Covers 10% of earth’s land, bigger than mountain glaciers
Snowline
A line marking the highest point at which a glacier's winter snow cover is lost during a given season.-Boundary between the zones of accumulation and wastage.
Rouche Mountonnee
Soothed streamlined hill cut into the bedrock.
What are striations?
Long parallel scratches left on bedrock from pebbles and gravel. Indicate direction of glacier.
CONTINENTAL GLACIATION
glaciers covering a large part of acontinent (>50 km2)
MEDIAL MORAINE
ridge of till formed where two adjacent lateral moraines
join and are carried down the glacier
glacial drift
refers to all sediments of glacial origin
types of glacial drift - till and stratified drift
End Moraine
Ridge of till that lies along the terminus of the valley glacier.
What is outwash?
Deposits made by glacial streams. Due to this, out wash is SORTED.
EQUILIBRIUM LINE
is the boundary between the zone of accumulation and the zone of ablation (marks to lowest position were snow remains all year)
glacier
a thick mass of ice that originates on land from the accumulation, compaction, and recrystallization of snow
What is another name for a continetal glacier?
An ice sheet.
What is calving?
The process of huge chunks of ice breaking off an ice sheet to form icebergs.
steps in the formation of glacial ice
-Snow accumulates
-Snowflakes become smaller, thicker, and more spherical as they are compressed
-Air is forced out
-Snow is recrystallized into a much denser mass of small grains called firn
-Is firn a mineral?
-Once the thickness of the ice and snow exceeds 50 meters, firn fuses into a solid mass of interlocking ice crystals – glacial ice
-Is glacial ice a rock?
How is a continental glacier distinguished from an alpine or valley glacier?
Size-- they exceed 5,000 square km.Location-- They are not confined to valleys.
What is internal deformation?
Occurs when ice and ice crystals move over and around each other.
inderect effects of the ice age
Indirect effects of Ice Age glaciers
Forced migration of animals and plants
Changed stream courses
Rebounding upward of the crust in former centers of ice accumulation
Worldwide change in sea level
Climatic changes
What is a ground moraine?
Material carried in the bottom of a glacier before it is deposited.
What is an ice front?
Point where ice melts as fast as it moves.
Do glaciers have a lot of force?
Yes, F=m*a and they have A LOT of mass.
proglacial lake
...
ice ages
periods of glaciation
Striations
The marks left from scratches
horn
[glacial] (pyramidal peak) results when several cirque glaciers gouge an individual mountain summit from all sides. (Matterhorn in the Swiss Alps)
drumlin
an oval mound of till
foraminifera
microscopic organism deep-sea remains put together chronology of ice volume (TEMP)
moraine
the accumulation of glacial till
Hanging Valley
Small abandoned glacial valley suspended on a mountain above the main glacial valley.
ice crystals
always advancing in a glacier
fjords
glacial troughs in mountainous coastal regions
Surges
Sometimes glaciers can have brief _______ and flow up to 500 times faster
sediment transport is ALWAYS in
ONE DIRECITON
plucking
freeze/thaw action helps pry loose blocks of material
transverse dune
dunes formed perpendicular to wind direction, very steep slip face (look almost like lines)
glacial erratic
An ice-transported boulder that was not derived from bedrock near its present site.
Plastic flow
Occurs within the ice
Under pressure, ice behaves as a plastic material
Kame
An irregularly shaped hill or mound composed of sand, gravel and till that accumulates in a depression on a retreating glacier, and is then deposited on the land surface with further melting of the glacier.
Abrasion
weathering in which rocks collide and scrape against each other
Equlibrium line
boundary between zone of accumulation and ablation
Surge
when a glacier flows hundreds of meters/day
50 meters
Glacier needs to be ______________ thick
Moraines
Similar to alpine moraines but usually much larger
Glaciation
modification of the land surface by the action of glaciers
The Three types of Glaciers
Alpine, Piedmont, Continental
Roches moutonne'es
An elongate mound of bedrock worn smooth and rounded by glacial abrasion.
Valley glacier-
long, narrow, wedge-shaped mass of ice that develops and usually moves through a mountain valley
Terminal Moraine
eroded rock material dropped at the front of a glacier
Glacial Budget
the balance, or lack of balance, between accumulation at the upper end of the glacier and loss at the lower end
Drum Lines
Glaciers that move older moraines from the material into elongated landforms.
Kettle
A small depression that forms when a chunk of ice is left in glacial till
Other types of glaciers
Ice caps
Outlet glaciers
Piedmont glaciers
from deposited ride of till
How do Moraines form?
lateral moraine
forms along each side of a glacier
kettle lake
glaciers that had chunks of the glacier break off then melts creating lakes
Erratic
rock moved by a glacier and placed when glacier melted
overdeepening
ability of the glacier to carve below local baselevel. Great Lakes
Crevasses
Cracks in the Glacier that forms when the glacier comes to a steep downward slope.
deposition
process in which sediment is laid down in new locations
tillites
evidence for long past ice ages is found in ancient glacial sediments that have hardened into rocks to form _____
parabolic dune
Dune that has a parabolic shape and has ends that extend into the wind
What type of moraine is most of NYS covered with?
terminal
Self Arrest
a technique that climbers use to stop from falling down a slope by digging an ice ax into the snow
Longitudinal Dunes
long ridges that are more or less parallel to the prevailing wind
zone of wastage
At low elevation where summer melting exceeds accumulation
mechanical weathering
process by which rock is split or broken into smaller pieces without changing its chemical composition, disintegration
ground moraine (till plain)
deposition of till generally spread across a surface hiding former landscape
Basal Sliding
Meltwater forms at the base of a glacier acting as a lubricant which causes
core sampling
when they look for certain fossils at the surface and underground that are usually found with oil deposits. example: pelecypod. ohio passes this test.
Roche Mountanee
(Rock mutton) French - a rock outcrop that has been molded by glacial ice into a specific shape by the movement of ice from one direction
Youngest to oldest
Wis, Ill, Kan, Neb...NOW KNOW MANY MORE
Esker
A ridge of sand and gravel that is formed by meltwater tunnels beneath a glacier
rock flour
as a glacier moves it grinds rocks producing a mixture of clay and silt sized particles
Cirque Lakes
A body of water that forms within a cirque.
Plasticity
The ability of a solid to flow like a liquid
where glaciers form
In areas that are always covered by snow. In such areas more snow fall than melts each year
Warm Based Glaciers
Glacial ice at the bedrock contact is at or above the freezing point. Lubricates the base of the glacier and allows the whole glacier to slide.
Valley Glacier
is a stream of ice that flows between steep rock walls from a place near the top of a mountain valley
Where are the types of deserts?
Rainshadow, polar, subtropical and coastal.
How do glaciers cause erosion?
They remove loose rock from the valleys through which they move
what is are cirques?
a bowl shaped depression that the head of a glaical valley.
Antartica and Greenland
10% of land that is covered by glacial ice
where do galciers form?
in areas where snow falls more than it melts
Circle the letter of each sentence that is true about how glaciers move.
A. Glacial flow happens in two ways: plastic flow and basal slip.
B.The movement of glacier depends upon the balance between accumulation and wastage.
C. Basal slip occurs because of gravity.
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