Chapter 18

Question 1

Permafrost

Answer 1

Ground (soil or rock) that stays below 0°C for two or more years and persists through at least one summer.

Question 2

Global permafrost distribution

Answer 2

25% of Earth’s land surface
(~50% of Canada and Russia, >80% of Alaska, ~20 % of China)

Question 3

Range of frozen ice conditions (5)

Answer 3

1. Permanent ice cover
2. Continuous permafrost (90-100%)
3. Discontinuous permafrost (50-90%)
4. Sporadic permafrost (10-50%)
5. Isolated permafrost (1-10%)

Question 4

Talik

Answer 4

Layer of year-round unfrozen ground that lies in permafrost areas. Classified as Through (larger section), closed (completely surrounded by permafrost), and open (exposed, usually underwater).

Question 5

Active permafrost layer thickness

Answer 5

0.5 - 2m

Question 6

Ground ice types (4)

Answer 6

1. Microscopic in pores
2. Segregated ice bodies
3. Ice wedges
4. Massive buried ice.

Question 7

Relict ice

Answer 7

Buried ice from the last glacial period that can be tens of meters thick.

Question 8

Oldest relict ice in North America

Answer 8

740,000 years old, found in central Yukon.

Question 9

Canadian permafrost thickness range

Answer 9

Ellesmere Island (>700 m) → Yellowknife (1-10 m)

Question 10

Canadian permafrost temperature range

Answer 10

Ellesmere Island (-15C) → Yellowknife (-1 C)

Question 11

Canadian ground ice content

Answer 11

0-100%. Microscopic in pores, visible as segregated ice bodies, wedges, massive ice.

Question 12

Local permafrost thaw

Answer 12

Surface movement changes the landscape, and impacts communities and infrastructure

Question 13

Global permafrost thaw

Answer 13

Carbon feedback. Twice as much carbon in permafrost as in the atmosphere.

Question 13

Thermokarst

Answer 13

Erosional process by which characteristic landforms result from the thawing of ice-rich permafrost and/or melting of massive ice.

Question 14

Effect of permafrost thaw on infrastructure

Answer 14

Permafrost has poor drainage that makes construction difficult. Fine grained material has the greatest loss of strength when thawed, and most heaving as freezes.

Question 15

Effect of permafrost thaw on roads

Answer 15

Road construction promotes melting of permafrost,
50% of roads in Northern Canada built on permafrost are at risk of becoming unstable.
The older technique using a layer of gravel to insulate the ground no longer works as temperatures rise. A solution is a layer of large stones and light colored materials.

Question 16

Effect of permafrost on runways

Answer 16

Paved runways are more expensive to build and maintain than gravel runways. Most airports in Nunavut and NWT are gravel, however, modern jets cannot use them.