Glacial Motion and Deposition Flashcards
The mass balance of a glacier is any net _____ or net _____ of ice.
gain, loss
What is mass balance?
any net gain or net loss of ice
Net gain is ______ of ice
accumulation
Net loss is _______ of ice
ablation
what is the single most important factor on whether a glacier is growing or shrinking?
summer temperature
During the winter months _____ falls and recharges the glacier in the uphill areas and flows downhill
snow
Where do glaciers melt in the summer?
at the terminus
Glacial motion occurs due to _____
gravity
Ice in a glacier behaves like a _____ until you get 50 meters deep, where the ice gets more plastic/moldable
solid
Glaciers flow _______
downslope
glaciers move _____ at less than ___ inches per day
slowly, 10
Increased weight or pressure on ice causes the crystal ____ to align which causes the ice to be more moldable
axes
What two processes do glaciers move by?
- Internal flow
- basal sliding
what happens during internal flow?
after the crystal axis align, they can mold and ooze past one another.
Is internal flow fast or slow?
slow - molecule to molecule movement
Is Basal sliding a slow or rapid process?
rapid
basal sliding happens as a result of ____ moving against the ground surface below it.
ice
the movement of ice against the ground surface creates ______ which produces _____ which causes ____
friction, heat, melting.
As melt water accumulates at the basis of a glacier it acts as a _______ for the glacier to slide down on top of
lubricant
Glaciers are the most powerful _____ of erosion
agents
Glaciers can pick up large rocks from the ground and _____ them to different locations
move
Glaciers erode efficiently by…
- filing rock surfaces smooth
- Plowing rocks from the ground
- Transporting sediments
How are rocks filed and plowed by glaciers?
- rock fragments are carried within the glacier
- Near the base, rock fragments scrape the ground
Near the base, rock fragments ______ the ground.
scrape
What happens to rock fragments near the ground?
they scrape the ground
When large rock fragments scrape the ground they cause…
glacial striations
rock fragments at the base of a glacier can rub and scratch ______ into the rocks that they are moving over.
grooves
- called glacial striations
Glacial Striations help us understand the _______ that glaciers moved over the surface
direction
What are the four distinctive land marks that mountain glaciers produce?
- cirques
- arete
- Horns
- U-shaped valleys
What are cirques?
bowl-shaped depressions at the head of the glacier.
______ are sharp ridges between valleys
aretes
what are horns?
pyramidal peaks from which a number of valley glaciers descend
How are horns developed?
when cirques are cut out on all sides of a mountain
Glaciers ______ a lot of sediment
deposit
what is the main feature that distinguishes glacially deposited sediment from sediment that is deposited by streams or wind?
sediment deposited by glaciers is not sorted
When glaciers pick up sediments they pick up different ______ sediments and move them ______
sized, together
The sediment deposed by glacial erosion is _____.
unsorted
Unsorted rock and sediment is called ____
till
What is glacial till?
Unsorted rock and sediment
what is a distinct glacial depositional feature?
Moraines
What are moraines?
narrow ridges of deposited materials
How are moraines categorized?
They are given different names according to where they form in the glacier
_____ moraines form along the sides of a glacier
lateral
Where do lateral moraines form?
along the sides of a glacier
Where do terminal moraines form?
at the end of a glacier
Converging glaciers leave a ridge of till called a _____ moraine
median
Where do medial moraines form?
in the middle of a glacier, especially when two glaciers combine
What are two other depositional glacier features?
- Kettle lakes
- eskers
what are eskers?
raised beds that are formed underneath the glaciers by sediment left behind from meltwater streams in a glacier’s body
How are kettle lakes formed?
As glaciers dig out pockets of ground those pockets fill with water from the trapped ice left behind in the deposited till/outwash
Kettle lakes form as glaciers dig out pockets of ____ and then those pockets fill with ____
ground, water
Trapped ice left behind in the deposited till creates _____ ____
kettle lakes
Melt water streams in a glacier’s body leave behind sediment in a raised bed called an ______.
esker
