Lecture 16: Cryosphere Part 2

Question 1

How does snow transform into ice?

Answer 1

Some snow survives the summer melt and is buried by successive snowfall.

• Then summer melting creates granular ice: Neve
• Pressure of the overlying snow starts to compact “snow” that survives one or more full seasons of melt (ablation): Firn
• Further compaction eventually forms ice

Question 2

How are glaciers able to flow and where is flow the fastest?

Answer 2

Because ice crystals deform under stress.

-Flow fastest in centre and slowest at edges

Question 3

What are the two classes of glaciers?

Answer 3

1. Warm-based ice

2. Cold-based ice

Question 4

What is warm-based ice glaciers?

Answer 4

Is close to the freezing point and has liquid water

Question 5

What is cold-based ice glaciers?

Answer 5

Is below the freezing point throughout

Question 6

What is accumulation?

Answer 6

Addition of mass to a glacier

Question 7

What is ablation?

Answer 7

Removal of mass from a glacier

Question 8

What is the equilibrium line?

Answer 8

The boundary between the accumulation and ablation zones, where net ablation = net accumulation

Question 9

What is mass balance?

Answer 9

The difference between the amount of material that a glacier accumulates and the amount lost during ablation.

Question 10

What causes striations and/or chatter marks?

Answer 10

Debris frozen into the base of the ice that is dragged along the surface, gouging it, as the glacier moves.

Question 11

How are u-shaped valleys formed?

Answer 11

Gouged out by main trunk glacier

Question 12

How are hanging valleys formed?

Answer 12

Tributary valley well above main valley floor carved by tributary glaciers

Question 13

What are cirques?

Answer 13

Bowl-shaped valley formed at glacier head

Question 14

What are aretes?

Answer 14

Sharp-edged ridges

Question 15

What are horns?

Answer 15

Pointed pyramidal peaks

Question 16

What are (pro)glacial lakes?

Answer 16

Lakes that form in front or along the margins of a glacier.

Question 17

What is an outwash?

Answer 17

Gravel and sand deposits, deposited by meltwater beyond the terminus of a glacier

Question 18

What is a till?

Answer 18

Unsorted sediments deposited by a glacier

Question 19

What are five forms of moraines?

Answer 19

1. End moraines: form at the terminus of a glacier
2. Terminal moraines: marks the glaciers furthest advancement
3. Recessional moraines: marking the retreat of the glacier
4. Lateral moraines: form along the sides of the glacier
5. Medial moraines: form when two glaciers join, merging their lateral moraines

Question 20

What are drumlins and eskers and how do they form?

Answer 20

Drumlins: form when ice sheets mold subglacial sediments creating tear-dropped hills
Eskers: rivers flowing beneath the ice that leaves ridges of well-sorted sand and gravel

Question 21

What are kames and how do they form?

Answer 21

A hill/hummock or terrace composed of stratified sand and gravel laid down by glacial meltwater.

Question 22

What are kettles and how do they form?

Answer 22

A depression/lake formed in locations of large ice blocks calved from receding glaciers

Question 23

What are moraines?

Answer 23

Accumulations of till

Question 24

What are some reasons glaciers are important?

Answer 24

• Its ice holds records of past environments

- Can help us understand the relationship between temperature, greenhouse gasses, solar radiation, and changing climate