!GLG 101-Illustrated Vocabulary-Chapter 12
!Glaciers
copyright 2003-Roger Weller
!alpine glacier
*a valley glacier
!Alps
*a prominent mountain range in southern Europe
!arete
*a skinny mountain ridge shaped on opposite sides by a series of glacial cirques
!avalanche
*a large mass of snow that rapidly slides down a slope
!bergschrund
*the large crack at the top of a valley glacier where it is pulling away from the mountain
!cirque
*a scoop-like depression on the side of a mountain formed by a valley glacier eroding the
mountain.
*[Rocky Mountains Park-Cirque-1]
*[Rocky Mountains Park-Cirque-2]
!continental glaciation
*glaciers cover a large portion of a continent. Modern examples are Greenland and the
Antarctic.
!crevasse
*a very large crack on top of a glacier
!crustal rebound
*during an ice age the weight of a thick continental glacier presses the crust of the earth
down; after the glacier melts, the crust slowly rises up to its previous elevation.
!drumlin
*a long, skinny, cigar-shaped hill that has be sculpted by a glacier flowing over it*
!erratic
*a boulder far removed from its original source and deposited by a glacier.
*[Yosemite-Glacial grooves and erratics-3]
!esker
*a snakelike ridge of water lain gravel deposited by a steam flowing beneath a melting
glacier
!fiord
*a U-shaped glacial valley that is partially flooded by seawater
!firn
*glacial ice, a granular form of ice similar to the material in a "slush ball"
!frost wedging
*Water gets into a crack, freezes, and expands; the tremendous pressures exerted by the
expansion of water into ice can cause the rock to split further.
!glacial grooves
*as a glacier moves across bedrock the large rocks that the glacier is dragging along
gouge long grooves.
*[Yosemite-Glacial grooves]
!glacial plucking
*the process where glacial ice is frozen in cracks and as the glacier moves, the ice pulls
rock fragments out of the bedrock
!glacial polish
*a glacier moving across a bedrock surface can polish the bedrock by abrasion with the
fine rock rock material embedded in the ice.
*[Yosemite-Glacial polish-1]
*[Mt. Whitney-Glacial polish-2]
!glacial striations
*scratches left on boulders and cobbles as they are dragged along by a glacier and rubbed
against each other during the movement
!glacial till
*the unsorted rock debris, ranging from boulders to silt, that are left behind when a
glacier melts.
!glacier
*a moving mass of ice on land that is at least 150 feet thick
!hanging valley
*a small U-shaped glacial valley exposed on the upper side of a larger U-shaped glacial
valley; the smaller valley was formed in colder times by a tributary valley glacier meeting
up with a larger valley glacier.
!horn
*a mountain with very steep slopes which was carved with cirques on three or more by
valley glaciers; the most famous one is the Matterhorn in Switzerland.
*[Rocky Mountains Park-Horn and Cirques]
!ice ages
*distinct times in the history of the Earth when major portions of the continents were
covered by glaciers.
!kettle
*a small lake surrounded by glacial till; formed by a depression created by the melting of
a large piece of glacial ice covered over with till.
!lateral moraine
*the piles of glacial till deposited at the terminal end of a glacier
!loess
*a very fine, silty material that started out as rock flour (rocks ground up by glacial action
to a fine poweder), but is now a wind-deposited soil.
!medial moraine
*when two two valley glaciers merge to form a larger valley glacier, their area of contact
is often marked by a line of glacial debris accumulated from lateral moraines of the two
glaciers.
!outwash plains
*flat land areas covered by the silty material carried by streams flowing away from a
melting glacier
!permafrost ground
*semipermanent frozen ground
!rock flour
*rock that has been crushed and ground to a fine powder by glacial action.
!terminal moraine
*the piles of glacial till at the base (snout) of a glacier
!u-shaped valley
*is created when a valley scrapes out the bottom and sides of the valley that it is moving
through.
*[Rocky Mountains Park-U Shaped Valley-1]
!valley glacier
*a glacier in a mountain valley; also known as an alpine glacier
!Wisconsin Ice Age
*the most recent of the Pleistocene advances of glaciers moving across North America; it
ended about 15,000 years ago.
!zone of ablation
*the portion of a glacier below the snowline where the glacier is melting
!zone of accumulation
*the region of a glacier above the snow line where ice in the form of snow is being added
to the glacier.