Chapter 18 Vocab Flashcards
ablation
The removal of ice at the toe of a glacier by melting, sublimation (the evaporation of ice into water vapor), and/or calving.
arete
A residual knife-edge ridge of rock that separates two adjacent cirques.
Basal Sliding
The phenomenon in which meltwater accumulates at the base of a glacier, so that the mass of the glacier slides on a layer of water or on a slurry of water and sediment.
Cirque
A bowl-shaped depression carved by a glacier on the side of a mountain.
Continental Glacier (ice sheet)
A vast sheet of ice that spreads over thousands of square km of continental crust.
Crevasse
A large crack that develops by brittle deformation in the top 60 m of a glacier.
Drumlin
A streamlined, elongate hill formed when a glacier overrides glacial till.
End Moraine
A low, sinuous ridge of till that develops when the terminus (toe) of a glacier stalls in one position for a while.
Erratic
A boulder or cobble that was picked up by a glacier and deposited hundreds of kilometers away from the outcrop from which it detached.
Esker
A ridge of sorted sand and gravel that snakes across a ground moraine; the sediment of an esker was deposited in subglacial meltwater tunnels.
Fjord
A deep, glacially carved, U-shaped valley flooded by rising sea level.
Glacial Advance
The forward movement of a glacier’s toe when the supply of snow exceeds the rate of ablation.
Glacial Drift
Sediment deposited in glacial environments.
Glacial Outwash
Coarse sediment deposited on a glacial outwash plain by meltwater streams.
Glacially Polished Surface
A polished rock surface created by the glacial abrasion of the underlying substrate
Glacial Rebound
The process by which the surface of a continent rises back up after an overlying continental ice sheet melts away and the weight of the ice is removed.
Glacial Retreat
The movement of a glacier’s toe back toward the glacier’s origin; glacial retreat occurs if the rate of ablation exceeds the rate of supply.
Glacial Subsidence
The sinking of the surface of a continent caused by the weight of an overlying glacial ice sheet.
Glacial Till
Sediment transported by flowing ice and deposited beneath a glacier or at its toe.
Glacier
A river or sheet of ice that slowly flows across the land surface and lasts all year long.
Hanging Valley
A glacially carved tributary valley whose floor lies at a higher elevation than the floor of the trunk valley.
Horn
A pointed mountain peak surrounded by at least three cirques.
Ice Age
An interval of time in which the climate was colder than it is today, glaciers occasionally advanced to cover large areas of the continents, and mountain glaciers grew; an ice age can include many glacials and interglacials.
Iceberg
A large block of ice that calves off the front of a glacier and drops into the sea.
Ice - Margin Lake
A meltwater lake formed along the edge of a glacier.
Ice Shelf
A broad, flat region of ice along the edge of a continent formed where a continental glacier flowed into the sea.
Interglacial
A period of time between two glaciations.
Kettle Hole
A circular depression in the ground made when a block of ice calves off the toe of a glacier, becomes buried by till, and later melts.
Lateral Moraine
A strip of debris along the side margins of a glacier.
Loess
Layers of fine-grained sediments deposited from the wind; large deposits of loess formed from fine-grained glacial sediment blown off outwash plains.
Medial Moraine
A strip of sediment in the interior of a glacier, parallel to the flow direction of the glacier, formed by the lateral moraines of two merging glaciers.
Milankovic Cycles
Climate cycles that occur over tens to hundreds of thousands of years because of changes in Earth’s orbit and tilt.
Moraine
A sediment pile composed of till deposited by a glacier.
Mountain (alpine glacier)
A glacier that exists in or adjacent to a mountainous region.
Patterned Ground
A polar landscape in which the ground splits into pentagonal or hexagonal shapes.
Permafrost
Permanently frozen ground.
Plastic Deformation
The deformational process in which mineral grains behave like plastic and, when compressed or sheared, become flattened or elongate without cracking or breaking.
Pluvial Lake
A lake formed to the south of a continental glacier as a result of enhanced rainfall during an ice age.
Polar Glacier
A glacier so cold that its base remains frozen to the substrate.
Recessional Moraine
The end moraine that forms when a glacier stalls for a while as it recedes.
Roche Moutonnee
A glacially eroded hill that becomes elongate in the direction of flow and asymmetric; glacial rasping smoothes the upstream part of the hill into a gentle slope, while glacial plucking erodes the downstream edge into a steep slope.
Sea Ice
Ice formed by the freezing of the surface of the sea.
Tarn
A lake that forms at the base of a cirque on a glacially eroded mountain.
Temperate Glacier
A glacier with a thin layer of water at its base, over which the glacier slides.
Terminal Moraine
The end moraine at the farthest limit of glaciation.
Tidewater Glacier
A glacier that has entered the sea along a coast.
Toe
The leading edge or margin of a glacier.
U - Shaped Valley
A steep-walled valley shaped by glacial erosion into the form of a U.
Zone of Ablation
The area of a glacier in which ablation (melting, sublimation, calving) subtracts from the glacier.
Zone of Accumulation
(1) The layer of regolith in which new minerals precipitate out of water passing through, thus leaving behind a load of fine clay; (2) the area of a glacier in which snowfall adds to the glacier.
