Glaciation Pack N

Question 1

Where are periglacial landscapes?

Answer 1

• High latitudes (e.g. Northern Canada, Northern Russia, Fairbanks - Alaska)
• High mountains/altitudes (e.g. Himalayas)
• Continental interiors (e.g. Churapcha, Siberia)

Question 2

What is permafrost?

Answer 2

• Any ground that remains completely frozen for at least two years straight
• 25% of the Earth’s surface is permafrost, especially in the Northern hemisphere

Question 3

What are the characteristics of periglacial climates?

Answer 3

• Intense frosts and long winters
• Daily temperatures below 0°C for at least 9 months of the year and below -10°C for at least 6 months of the year
• Summers are rarely warmer than 18°C
• Highest annual temperatures range between 1°C and -4°C
• Low precipitation (less than 600mm per year)

Question 4

What types of permafrost exist?

Answer 4

• Continuous
• Discontinuous
• Sporadic

Question 5

What is continuous permafrost?

Answer 5

• Found in the coldest regions
• Mean annual surface temperature is -6°C or less
• Extends deep into surface layers of soil and rock for hundreds of metres
• Very thin active layer
  e.g. 1500m deep in Siberia

Question 6

What is discontinuous permafrost?

Answer 6

• Found in slightly warmer regions
• Ground isn’t frozen as deeply (+/-30m)
• There are gaps in permafrost where it is below water or close to the sea, due to the insulation
• More fragmented and thinner than continuous permafrost

Question 7

What is sporadic permafrost?

Answer 7

• Occurs at the margins of periglacial environments
• Fragmented and only a few metres thick
• Annual mean temperatures fluctuate around freezing
• In isolated spots where it is cold enough to prevent complete thawing during summer, like on shady hillsides or beneath peat

Question 8

What are the effects of melting permafrost?

Answer 8

• Permafrost soils contain large quantities of organic carbon from dead plants that couldn’t decompose due to the cold temperatures
• As it thaws, the material begins to decompose, which releases greenhouse gases (methane) into the atmosphere
• Villages are built on permafrost so houses, roads and other infrastructure is being destroyed

Question 9

What is the energy exchange buffer zone?

Answer 9

• The active layer and permafrost is shielded by tundra vegetation, an organic surface layer of litter and peat and snow cover
• This is known as the surface buffer zone
• The buffer zone has the ability to store and transmit heat, which controls the the behaviour of the active layer and the permafrost

Question 10

How is permafrost degraded by humans?

Answer 10

• Through the establishment of permanent settlements and the development of activities like mining, oil extraction and military use
• There are more permanent settlements and more use of resources in areas with periglacial climates
• Conventional construction alters the thermal balance of the ground and leads to permafrost thaw and ground subsidence
• Tundra and the snow layer are being cleared, which reduces the insulation for the active layers so it deepens as heat is more easily transferred to the permafrost
• Ice-rich areas that have a high porosity, are close to rivers, have fine grained sediment or lots of interstitial ice will cause the most ground subsidence
• Vehicle use and building and infrastructure (which give out large amounts of heat directly to the ground) also cause degradation
• Infrastructure, like roads, railways, bridges and airstrips, are impacted by ground subsidence

Question 11

Where is permafrost degradation happening?

Answer 11

• In Inuvik, Northern Canada the active layer deepened from 30cm to 183cm
• After the coniferous forest was cleared there was ground disturbance, an increase in the melting of ground ice and carbon was released from peat stores

Question 12

What can humans do to protect themselves against permafrost degradation?

Answer 12

• Traditional methods have been replaced by new more expensive methods
• House and other small building are raised 1m above ground on pipes so air can circulate and remove heat
• Larger structures (like roads, bridges and airstrips) are built on aggregate pads to substitute for the insulating effect of vegetation to reduce the transfer of heat
• Utilidors are used but these are only economic for larger settlements
• The Trans-Alaska pipeline is an example