Glaciers

Question 1

Ground ice forms:

Answer 1

Ground ice forms when pore water freezes in terrestrial substrates and accumulates as perennial permafrost.

Question 2

Shelves develop:

Answer 2

Shelves develop as piedmont glaciers fan out into coastal lowlands from outlet glaciers and float seawards of a grounding line when water depth reaches about 90% of ice thickness.

Question 3

Glaciers and ice sheets cover approaximately

Answer 3

Glaciers and ice sheets cover approximately 10% of the Earth’s surface

Question 4

Snow and ice is transferred

Answer 4

This snow and ice is then transferred down valley by glacier movement until it reaches areas where it is lost to the system, either by melting and evaporation or by the breakaway of ice blocks or icebergs, known as ablation

Question 5

Climatic factors on availability of ice

Answer 5

Climatically, the most important factor is the amount of energy available to melt ice, which in most areas is closely related to air temperatures. There is a close relationship between ablation and the number of days when temperatures are greater than 0 degrees C. The more positive degree day, the less the likelihood of ice persisting throughout the year.

Question 6

Topographical factors influencing glacier survival

Answer 6

Topographical factors influencing glacier survival are local slope and the presence of deep water at the glacier margin. Snow accumulating on or above steep slopes may avalanche down to lower altitudes where ablation rates are higher, and glaciers terminating in deep water lose large amounts of mass by the breakaway of icebergs, a process known as calving.

Question 7

Liquid water affecting glacier behaviour

Answer 7

Within and beneath glaciers and ice sheets, liquid water profoundly affects glacier behaviour, controlling rates of glacier flow and influencing the processes and rates of erosion and deposition.

Question 8

Transferrence from areas of accumulation to areas of ablation

Answer 8

Snow and ice is transferred from areas of accumulation to areas of ablation by glacier flow. Flow takes place by a variety of processes, which can be grouped together as sliding, deformation of the ice, and deformation of the glacier bed.

Question 9

Glacier motion occurs when:

Answer 9

Glacier motion occurs when the forces exerted by the weight and and surface slope of the ice overcome the strength of the glacier or its bed, allowing the ice to slide past obstructions on the bed, or the ice to deform like slow, semi-molten lava.

Question 10

Glaciers flow through a combination of

Answer 10

All glaciers flow through combination of internal deformation and basal sliding.

Question 11

Imbrie and Imbrie, 1979

Answer 11

One of the major achievements of Earth science in recent years has been to show that this sequence of glacial and interglacial periods is primarily driven by cyclical changes in the Earth’s orbit around the sun (Imbrie and Imbrie, 1979; Berger, 1988; Imbrie et al, 1992).

Question 12

Paterson, 1994

Answer 12

On any one glacier or ice sheet, ablation rates are usually three or four times the accumulation rates and, therefore, decay times should be one third to one quarter of growth times (Paterson, 1994).

Question 13

Lateral moraines

Answer 13

Lateral moraines are linked by terminal cross-valley moraines where the glacier sheds debris conveyed to its farthest limit.

Question 14

Deglaciation might be marked by

Answer 14

Deglaciation might be marked by a series of chevron moraines, each recording the receding ice margin