Chapter 19

Question 1

Glacier Formation

Answer 1

• snow compressed to granular form
• more compression= granules coalesce into neve/firn
• further compression leads to glacial ice

Question 2

Glacial flow/movement

Answer 2

glacial “flow” is the orderly sliding of ice molecules
- ice under extreme pressure deforms instead of slipping
- meltwater contributes surface for glaciers to slide on
- flow in response to overlying weight

Question 3

erosion of glaciers (BASICS)

Answer 3

volume and speed determine success of glacial erosion
erosive power of moving ice> that of water

Question 4

glacial plucking

Answer 4

picking up of rock material through refreezing of meltwater

Question 5

glacial abrasion

Answer 5

bedrock worn down by rock debris collected by the glacier

Question 6

transportation by glaciers

Answer 6

can move large rock pieces; typically move glacial flour; most rock material transported along the base of the ice
- remaining glacial ice is free of rock debris
- melt streams: role of flowing water on moving ice

Question 7

moulins

Answer 7

cracks in ice in which streams run

Question 8

deposition by glaciers

Answer 8

glaciers move lithospheric material from one region to another in a vastly different form

Question 9

drift

Answer 9

material moved by glaciers

Question 10

till

Answer 10

rock debris deposited by moving ice

Question 11

glacial erratics

Answer 11

large boulders that are different from surrounding local bedrock

Question 12

deposition by meltwater

Answer 12

large portion of debris carried by glaciers deposited or redeposited by meltwater; subglacial streams from glaciers carry sedimentary material

Question 13

deposition by ice sheets

Answer 13

irregular, uneven surface of deposition (till plain)

Question 14

Moraines

Answer 14

land consisting primarily of till; material left behind a moving glacier

Question 15

terminal moraine

Answer 15

marks outermost limit of glacial advance

Question 16

recessional moraine

Answer 16

positions where ice front is stabilized

Question 17

ground moraine

Answer 17

large quantities of till laid down under a glacier instead of from its edge, kettles

Question 18

continental ice sheets

Answer 18

exist in nonmountainous areas (Antarctica and Greenland); outlet glaciers

Question 19

highland icefields

Answer 19

ice sheets that submerge most underlying topography; valley and piedmont glaciers

Question 20

alpine glaciers

Answer 20

develop individually instead of as part of an ice field; cirque glaciers

Question 21

continental ice sheets: WHAT ARE THEY MADE OF

Answer 21

• composed of gravel, sand, and silt since meltwater is incapable of moving larger materials
• outwash plains, valley trains, eskers, kames, and lakes are very common
• stratified drift

Question 22

development of ice sheets

Answer 22

1. Pleistocene ice sheets originated in midlatitudes and subpolar regions
2. ice flowed outward from the center of accumulation
3. ice sheets ebbed and flowed with changing climate

Question 23

Pleistocene Glaciation (2.5 mya)

Answer 23

• last ice age
• refrigeration of high latitude and high elevation areas
• 1/3 of total land covered in ice

Question 24

causes of Pleistocene glaciations

Answer 24

• cold vs warm climate for glaciation
• role of Milankovitch cycles
• variation in solar output
• variation in CO2
• changes in continental positions
• atmospheric circulations

Question 25

mountain glaciers development

Answer 25

usually formed in sheltered depressions near heads of stream valleys

Question 26

mountain glaciers basic landform

Answer 26

basic landform in glaciated mountains is cirque
marks the location where an alpine glacier originated

Question 27

erosion by mountain glaciers (they do erode)

Answer 27

1. quarried fragments from the cirque are carried away when ice flows out of the cirque
2. cirque ice melts (the depression that holds water is a tarn)
3. several cirques cut back into interfluve and result in the spine of rock (arete)

Question 28

erosion in the valleys

Answer 28

• some glaciers never leave cirques
• principle erosive work is to deepen, steepen, and widen valley
• U-shaped glacial troughs

Question 29

primary mechanism of deposition by mountain glaciers

Answer 29

• continental ice sheets are more responsible for deposition than mountain glaciers
• primary deposition mechanism: moraines (lateral and medial)

Question 30

the Periglacial environment

Answer 30

• periglacial: on the perimeter of glaciation
• permafrost presence
• extends to great depths, patterned ground, proglacial lakes