Chapter 14 -- Glaciers and Glaciation Flashcards
> 99% of glacial ice is in ________ and _________
Cover about ##% of the Earth’s land surface
Antarctica and Greenland
10%
a mass of compacted and recrystallized ice that flows under its own weight (excludes: ___ ___ and ______ _______)
Glaciers
Sea Ice and Frozen Seawater
Long, narrow tongues of ice Typically much smaller than continental glaciers Flow from \_\_\_\_\_\_ to \_\_\_\_\_ elevations Confined within mountain valleys Also called \_\_\_\_\_\_/\_\_\_. \_\_\_\_\_\_\_
Valley Glaciers
Higher to Lower
Alpine/Mtn. Glacier
Cover large areas and are not confined by topography
Flow outward in all directions from the center of accumulation
Present today in _________ and __________, with ice thicker than #,### meters.
Covered large parts of North America from Washington to Maine during the Pleistocene.
Continental Glaciers
Antarctica and Greenland
3,000
Similar to continental glaciers but much smaller
Some develop from valley glaciers when they grow over the top of a divide.
Ice Caps
Glaciers Contain a little more than #% of all water on Earth ##% of all the fresh water are located here. Store this water for long periods, but melting and sublimation return it to the hydrologic cycle.
2%
75%
A process by which ice turns into water vapor without an intermediate liquid phase.
Sublimation
Compaction of snow and elimination of pore space results in a granular ice called ____
Further burial recrystallizes _____ into _______ ___.
Fresh snowflakes are about ##% air.
Firn
Glacial Ice
80%
Glaciers may slide down slope over their underlying surface, a phenomenon called _____ ____.
Basal Slip
Most of their movement is accomplished by ______ ____, a type of deformation that takes place in response to stress.
Plastic Flow
Glaciers can be described in terms of their ______.
Budget
Upper part of a glacier where snow is covered year around.
Zone of Accumulation
Lower are where losses (_______) exceed gain.
Zone of Wastage
melting
Elevation to which snow melts during the warm season.
Firn Limit
if firn limit moves down the glacier.
+ ve Budget
if firn limit moves up the glacier.
- ve Budget
As glaciers move down river valleys, they widen, deepen, and straighten the valley.
U-Shaped Valley Trough
Smaller tributary glacial valleys left stranded high above more quickly eroded central trunk valleys.
Hanging Valleys
Steep sided, half bowl shaped recesses carved into mountains at the heads of glacial valleys.
Cirques
Water filled cirque.
Tarn
Sharp ridges separating glacial valleys.
Aretes
Sharp peaks remaining after cirques have cut back into a mountain on several sides.
Horns
Coastal inlets formed by drowning of glacially carved valleys by rising sea level.
Fiords
are boulders that are found far from their source and eroded and transported by glaciers.
Erractics
is unsorted, unstratified sediments deposited directly by glacial ice.
Till
Is layered and sorted to some degree; deposited in lakes or braided streams associated with glaciers.
Stratified Drift
Vast blankets of sediment that form in front of the glacier as it melts.
Outwash Plains
Deposits of braided streams that form long, narrow deposits of stratified drift.
Valley Trains
Conical hills created when a stream deposits sediment in a depression on the glacier’s surface.
Kames
Snake like deposits from sub glacial streams.
Eskers
Consist of couplets of dark and light, laminated, fine grained sediment
Represent seasonal deposition
Varves
Are probably rafted into lakes by ice blocks.
The ___ of a glacial lake may be determined by counting the layers.
Dropstones
Age
Proposes that minor irregularities in the Earth’s rotation and orbit can alter the amount of solar radiation received by the Earth and thereby affect climate.
The Milankovitch Theory
Orbital Eccentricity has a ________ year cycle.
100,000 Years
1.5° variance in tilt of axis has a ______ year cycle
41,000 Years
Precession of Axis has ____ year cycle.
23,000 Years
