Chapter 17

Question 1

Ice sheets

Answer 1

Permanent layer of ice covering an extensive tract of land, especially polar regions. (EX: Laurentide in Canada 10,000 years ago)

Question 2

Ice shelf

Answer 2

Floating sheet of ice permanently attached to a landmass, an extension of an ice sheet.

Question 3

Ice caps

Answer 3

Smaller ice sheets (less than 50,000 square km)

Question 4

Ice streams

Answer 4

Fast moving regions of an ice sheet. (EX: Antarctica, 50 km wide 800 m/year)

Question 5

Alpine glaciers

Answer 5

Formed in valleys originally occupied by streams, have velocities up to several m/year, and are 10 –100 km in length. Creates hanging and U-shaped (trough) valleys that when flooded becomes fiords;
cirques that become tarns when ice is gone; aretes and Horns (peaks)

Question 6

Outlet glaciers

Answer 6

Allow ice to move downhill away from an ice sheet or ice cap.

Question 7

Piedmont glaciers

Answer 7

Occur at the base of a mountain.

Question 8

Formation of glacial ice

Answer 8

Similar to metamorphism in that the ice changes from one solid form (snowflakes) to another (ice crystals).

Question 9

Internal deformation of glaciers

Answer 9

Occurs within glaciers where pressure is high enough to allow plastic deformation. Above this depth, ice is brittle and crevasses form.

Question 10

Basal slip

Answer 10

When ice is frozen to a bed, or lubricated by water

Question 11

Soft bed deformation from ice

Answer 11

Occurs where bedrock is weak enough to deform with ice.

Question 12

Antarctic glacial movement rate

Answer 12

1-2m/yr

Question 13

Outlet glacier movement rate

Answer 13

800m/yr

Question 14

Accumulation zone

Answer 14

Snowfall exceeds summer melt.

Question 15

Ablation zone

Answer 15

Summer melt exceeds snowfall.

Question 16

Mass balance (budget) of glaciers

Answer 16

Depends on relative amounts of accumulation and ablation. When accumulation is greater the glacier advances, when ablation is greater the glacier retreats. Separated by an equilibrium line with elevation ranging from 0-5km.

Question 17

Glacial erosion (2)

Answer 17

1. Plucking produces blocks similar to frost wedging
2. Abrasion grinds down bedrock to produce rock flour and gives glacial streams a milky appearance/lakes a blue color.

Question 18

Glacial deposition/drift

Answer 18

Glacial deposits are found in virtually the whole of Canada
Less (minimal) chemical weathering than in river sediments, so minerals such as hornblende and feldspars are common

Question 19

Till

Answer 19

Material directly deposited by glaciers. Poorly sorted. Becomes tillite when lithified.

Question 20

Stratified Drift

Answer 20

Material deposited by meltwater into outwash plains and valley trains. Sorted by size/weight of particles.

Question 21

Kettles

Answer 21

As a glacier retreats blocks of ice can become buried. When they melt, a pit is formed.

Question 22

Ice-contact deposits

Answer 22

Formed during retreat by fluvial processes and include eskers and kames

Question 23

End moraine

Answer 23

Terminus of alpine glacier or ice sheet when there is a period of equilibrium

Question 24

Ground moraine

Answer 24

Deposited as glacier advances. Smooths surface and fills in holes

Question 25

Terminal moraine

Answer 25

Ground moraine that records the greatest extent of the ice.

Question 26

Recessional moraine

Answer 26

Formed by a temporary pause in the retreat of a glacier/ice sheet.

Question 27

Drumlins

Answer 27

Small hills made of reshaped glacial till. Can also contain sand and gravel. Tear drop shaped from ice movement.

Question 28

Ice ages

Answer 28

Times when major ice sheets developed at the poles and extended to lower latitudes. Geological record shows 5 major ice ages.

Question 29

Pleistocene

Answer 29

Period of time (2,588,000 – 12000 years ago) where ~20 warm-cold climatic cycles happened. Glaciers covered 30% of Earth’s land.

Question 30

Holocene

Answer 30

Time (12,000 – today) since the last major ice age.

Question 31

Causes of ice ages (5)

Answer 31

1. Changes in earth’s orbit (eccentricity, obliquity, precession)
2. Plate tectonics (continental drift)
3. Glacial rebound (asthenosphere movement)
4. Sea level change
5. Proglacial lakes (lakes created by the weight of ice)

Question 32

Earth’s present eccentricity

Answer 32

0.017

Question 33

Earth’s present obliquity

Answer 33

23.44°

Question 34

Precession period

Answer 34

20,000 years