3b.Periglacial

Question 1

Periglacial Environments

Answer 1

Defined as areas with

• Permafrost
• Seasonal temp variations
• Freeze-thaw / frost heave
• High latitude areas
• 25% of earths surface (50% in past)

Question 2

Permafrost

Answer 2

• Impermeable
• Frozen for 2 or more years
• Thaws to form active layer
• Continuous: coldest regions, little thawing
• Discontinuous: Slightly warmer regions, freezing conditions dont penetrate deep, not all of area is frozen
• Sporadic: mean annual temps around freezing or below, appears in isolated spots

Question 3

Active layer

Answer 3

• Surface layer that thaws
• Can be 5m deep
• Active layer refreezes surface down and from ground up
• Leaves unfrozen area in middle
• Cold eventually freezes entire layer

Question 4

Frost heave

Answer 4

• Sub surface process
• Vertical sorting of material in active layer
• Stones heat and cool faster than surroundings due to low specific heat capacity
• Water beneath stones freezes & expands (9 %- 10%) pushing stone up
• Ground ice also pushes surface up (dome)

Question 5

Landforms

Answer 5

• Patterned ground
• Pingos (open system / east Greenland)
• Pingos (Closed system / Mackenzie)

Question 6

Patterned ground

Answer 6

• Stones moved via frost heave
• Creates network of stones / polygons
• Shapes can vary due to gravity / slope angle

Question 7

Pingos - east greenland

Answer 7

• Form in valley bottoms
• Water from surroundings collects due to gravity, freezes & expands under artesian pressure
• Artesian pressure: water pulled down by gravity —> loss in PE, gain in KE
• Forces land to dome up

Question 8

Pingos - Mackenzie

Answer 8

• Develop beneath lake where there is water
• Permafrost grows (cold)
• Ground water trapped by permafrost
• Talik (unfrozen ground) compressed by expanding permafrost (into a ball)
• Talik eventually freezes, and expands pushing land up

Question 9

Modification of Landforms

Answer 9

• Patterned ground colonised

- Pingos collapse due to temps rising

Question 10

Tundras

Answer 10

• Too cold for trees to grow, high latitude / altitude
• Arctic tundra in Greenland, north Russia, Canada
• Antarctic tundra in islands around Antarctica
• Grass, shrubs, mosses, lichen
• Seals, penguins, seabirds, hares, foxes, bears

Question 11

Why tundras are fragile

Answer 11

• Struggle to recover from damage
• Harsh climate
• Short growing season, little time to recover from damage
• Limited diversity
• Only adapted to cold, not warming climate
• Slow decay
• Wide fluctuations in food chain due to numbers changing rapidly

Question 12

Why tundras are a wilderness

Answer 12

• Typical perception of a cold place
• Extremely remote, inaccessible
• Conservationist think its worth preserving
• Scientifically valuable due to genetics
• Exploitable reasons