Chapter 18 Vocab

Question 1

ablation

Answer 1

The removal of ice at the toe of a glacier by melting, sublimation (the evaporation of ice into water vapor), and/or calving.

Question 2

arete

Answer 2

A residual knife-edge ridge of rock that separates two adjacent cirques.

Question 3

Basal Sliding

Answer 3

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.

Question 4

Cirque

Answer 4

A bowl-shaped depression carved by a glacier on the side of a mountain.

Question 5

Continental Glacier (ice sheet)

Answer 5

A vast sheet of ice that spreads over thousands of square km of continental crust.

Question 6

Crevasse

Answer 6

A large crack that develops by brittle deformation in the top 60 m of a glacier.

Question 7

Drumlin

Answer 7

A streamlined, elongate hill formed when a glacier overrides glacial till.

Question 8

End Moraine

Answer 8

A low, sinuous ridge of till that develops when the terminus (toe) of a glacier stalls in one position for a while.

Question 9

Erratic

Answer 9

A boulder or cobble that was picked up by a glacier and deposited hundreds of kilometers away from the outcrop from which it detached.

Question 10

Esker

Answer 10

A ridge of sorted sand and gravel that snakes across a ground moraine; the sediment of an esker was deposited in subglacial meltwater tunnels.

Question 11

Fjord

Answer 11

A deep, glacially carved, U-shaped valley flooded by rising sea level.

Question 12

Glacial Advance

Answer 12

The forward movement of a glacier’s toe when the supply of snow exceeds the rate of ablation.

Question 13

Glacial Drift

Answer 13

Sediment deposited in glacial environments.

Question 14

Glacial Outwash

Answer 14

Coarse sediment deposited on a glacial outwash plain by meltwater streams.

Question 15

Glacially Polished Surface

Answer 15

A polished rock surface created by the glacial abrasion of the underlying substrate

Question 16

Glacial Rebound

Answer 16

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.

Question 17

Glacial Retreat

Answer 17

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.

Question 18

Glacial Subsidence

Answer 18

The sinking of the surface of a continent caused by the weight of an overlying glacial ice sheet.

Question 19

Glacial Till

Answer 19

Sediment transported by flowing ice and deposited beneath a glacier or at its toe.

Question 20

Glacier

Answer 20

A river or sheet of ice that slowly flows across the land surface and lasts all year long.

Question 21

Hanging Valley

Answer 21

A glacially carved tributary valley whose floor lies at a higher elevation than the floor of the trunk valley.

Question 22

Horn

Answer 22

A pointed mountain peak surrounded by at least three cirques.

Question 23

Ice Age

Answer 23

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.

Question 24

Iceberg

Answer 24

A large block of ice that calves off the front of a glacier and drops into the sea.

Question 25

Ice - Margin Lake

Answer 25

A meltwater lake formed along the edge of a glacier.

Question 26

Ice Shelf

Answer 26

A broad, flat region of ice along the edge of a continent formed where a continental glacier flowed into the sea.

Question 27

Interglacial

Answer 27

A period of time between two glaciations.

Question 28

Kettle Hole

Answer 28

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.

Question 29

Lateral Moraine

Answer 29

A strip of debris along the side margins of a glacier.

Question 30

Loess

Answer 30

Layers of fine-grained sediments deposited from the wind; large deposits of loess formed from fine-grained glacial sediment blown off outwash plains.

Question 31

Medial Moraine

Answer 31

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.

Question 32

Milankovic Cycles

Answer 32

Climate cycles that occur over tens to hundreds of thousands of years because of changes in Earth's orbit and tilt.

Question 33

Moraine

Answer 33

A sediment pile composed of till deposited by a glacier.

Question 34

Mountain (alpine glacier)

Answer 34

A glacier that exists in or adjacent to a mountainous region.

Question 35

Patterned Ground

Answer 35

A polar landscape in which the ground splits into pentagonal or hexagonal shapes.

Question 36

Permafrost

Answer 36

Permanently frozen ground.

Question 37

Plastic Deformation

Answer 37

The deformational process in which mineral grains behave like plastic and, when compressed or sheared, become flattened or elongate without cracking or breaking.

Question 38

Pluvial Lake

Answer 38

A lake formed to the south of a continental glacier as a result of enhanced rainfall during an ice age.

Question 39

Polar Glacier

Answer 39

A glacier so cold that its base remains frozen to the substrate.

Question 40

Recessional Moraine

Answer 40

The end moraine that forms when a glacier stalls for a while as it recedes.

Question 41

Roche Moutonnee

Answer 41

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.

Question 42

Sea Ice

Answer 42

Ice formed by the freezing of the surface of the sea.

Question 43

Tarn

Answer 43

A lake that forms at the base of a cirque on a glacially eroded mountain.

Question 44

Temperate Glacier

Answer 44

A glacier with a thin layer of water at its base, over which the glacier slides.

Question 45

Terminal Moraine

Answer 45

The end moraine at the farthest limit of glaciation.

Question 46

Tidewater Glacier

Answer 46

A glacier that has entered the sea along a coast.

Question 47

Toe

Answer 47

The leading edge or margin of a glacier.

Question 48

U - Shaped Valley

Answer 48

A steep-walled valley shaped by glacial erosion into the form of a U.

Question 49

Zone of Ablation

Answer 49

The area of a glacier in which ablation (melting, sublimation, calving) subtracts from the glacier.

Question 50

Zone of Accumulation

Answer 50

(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.