Module 11

Question 1

permafrost

Answer 1

rock or soil material that has remained below 0 degrees for two or more years. the upper surface thaws in the summer and is considered the active layer

Question 2

why is permafrost important to canadians

Answer 2

40% land underlain by permafrost. 10-15% of Earths total land area

Question 3

periglacial environments

Answer 3

areas/regions where landforms and geomorphic processes are influenced by seasonal thawing and freezing, often in areas of permafrost

Question 4

distribution of permafrost in high latitude areas (arctic regions)

Answer 4

continuous permafrost, up to 700 m thick

Question 5

temp required for continuous permafrost

Answer 5

annual air temps <-7 degrees

Question 6

distribution of permafrost towards south (south of tree line)

Answer 6

discontinued, thins to only a few metres, patchy and sporadic

Question 7

temp required for discontinuous permafrost

Answer 7

mean annual air temps >-7 degrees

Question 8

ground ice

Answer 8

frozen moisture below earth’s surface. varies from small amount in pore spaces to large ice bodies

Question 9

ways ground ice forms

Answer 9

pingo ice, ice wedges, polygonal ground

Question 10

pingo ice

Answer 10

relatively clear permafrost, occurs horizontally or in lens-shaped masses. 3-54m in height and 30-450 in diameter.

Question 11

largest pingo in NA

Answer 11

Ibyuk pingo of Tuktoyaktuk in Northwest Territories

Question 12

ice wedges

Answer 12

permafrost formed in large ice wedges of masses with parallel or subparallel foliation. Foliated ice occurs as wedges, vertical or inclined sheets. 2.5cm-3m high, and 0.3 to 9m diameter.

Question 13

polygonal ground

Answer 13

micro-relief pattern on the ground where ice wedges are below the polygons. they are indicative or periglacial environments. each mound is less than 1 m but they cover thousands of metres in the Arctic

Question 14

causes of melting of the ice

Answer 14

erosion of stream banks, and the process thermokarst

Question 15

thermokarst

Answer 15

erosional process unique to permafrost. process by which characteristics landforms results from the thawing of ice-rich permafrost and/or melting of massive ice

Question 16

what does thermokarst cause

Answer 16

decreases the stability of the ground, landslides, thaw lakes, ground subsidence (road disturbance and house collapse), and freeze-thaw process

Question 17

freeze-thaw process

Answer 17

water expands by 9% when frozen which can fracture rocks. it produces frost-shattered screes.

Question 18

ice growth

Answer 18

occurs preferentially below stones in soil and forms pipraker. ice lifts stones/soil (frost heaving)

Question 19

pipraker

Answer 19

needle ice

Question 20

what does heaving produce

Answer 20

stone polygons and stone stripes

Question 21

slope processes

Answer 21

active layer has high water pressures, so it is prone to mass movement and solifluction lobes/terraces. there is a slow downslope movement of soil (couple cm/yr)

Question 22

creep

Answer 22

very slow rates of movement (<5mm/year) but can affect the stability of built structures such as pipes

Question 23

what gasses does permafrost release

Answer 23

carbon dioxide and methane