peri-glacial landforms

Question 1

what three things can define a peri glacial landscape

Answer 1

• freeze thaw cycle dominating geomorphic processes
• seasonal temperature variations
• permafrost

Question 2

what are the three types of periglacial landforms

Answer 2

• sorted stone polygons
• pingos
• patterned ground

Question 3

what is frost heave

Answer 3

a sub surface process that leads to the verticle sorting of material in the active layer

Question 4

describe the process of frost heave in three steps

Answer 4

• stones within fie material have lower specific heat capacity than their surroundings therefore heat up and cool down faster
• as the ground below freezes the rocks will be pushed upwards due to expansion
• this causes a domed surface

Question 5

explain how ground ice also contributes to domed ground

Answer 5

during summer melting periods, water percolates at the ground surface. in winter, this water re freezes and is unable to move downwards to the permafrost below to expands upwards.

Question 6

what are sorted stone polygons

Answer 6

large stones eventually reach the surface due to frost heave and fall around and accumulate at the edge of domed ground due to gravity

Question 7

what is patterned ground

Answer 7

a collective term for a number of smaller periglacial features being concentrated in one area. features include stone plygons and stone stripes

Question 8

what is a specfic example of patterned ground

Answer 8

burrow in alaska

Question 9

what are pingos and how big can they get

Answer 9

essentially pingos are ice cored rounded hills , they can be up to 90m in height and 800m in diameter

Question 10

what are the two types of pingo

Answer 10

open and closed system pingos

Question 11

how do open system pingos form

Answer 11

-form in valley bottoms when water from surrounding slopes collects in a talik which freezes under artesian pressure, forcing the overlying ground upwards due to expansion

Question 12

give a specific example where open system pingos are common

Answer 12

east greenland

Question 13

how do closed system pingos form

Answer 13

• water is collected in a talik from a direct source which will be a lake above
• in cold periods, the permafrost below grows and lake above freezes, causing the talik to be under hydrostatic pressure.
• when the talik itself eventually freezes it forces up the overlying sediments

Question 14

give a specific example where closed system pingos are common

Answer 14

the mackenzie delta in canada

Question 15

describe three types of modification for periglacial landforms

Answer 15

• as temperatures rise as the end of a periglacial period, patterned ground can be colonised by vegetation making it difficult to spot
• mass movement by creep can also degrade frost heave domes
• as temperatures increase pingos will collapse as their core ice thaws, this causes a circular depression in the ground known as an ognip.

Question 16

name one way in which material flows periglacial systems are impacted by oil extraction

Answer 16

gravel pads, the extraction of gravel from river beds to use as a base for road construction

Question 17

what are two ways in which the use of gravel pads effect material flows

Answer 17

• alters the rate in which material is transported and deposited downstream
• affects the equilibrium between erosional and depositional processes

Question 18

name two ways that energy flows are affected

Answer 18

• release of gas during drilling

- heat released from infastructure

Question 19

how are gases released during drilling and why is this negative for periglacial environments

Answer 19

-flaring involves the burning of gases, mostly it is C02 that is used. others including methane are vented into the atmosphere without burning. Both of these are potent greenhouse gases which will contribute to the enhanced greenhouse effect, raising temperatures on a local and global scale.

Question 20

how can infrastructure release heat

Answer 20

poorly insulated buildings will release heat

Question 21

what is an example of a town in alaska where temperatures have risen due to gas release and infastructure

Answer 21

in burrow, alaska, temperatures have risen 2.2 degrees above surrounding rural areas.

Question 22

how does the release of heat change landscapes

Answer 22

• melting permafrost and increasing the melting season for the active layer.
• this can result in subsidence and increased mobility of the land, allowing a type of mass movement called solifluction

Question 23

describe solifluction

Answer 23

-the downslope movement of thawed land resulting in solifluction lobes.