Permafrost is ground that stays at or below 0 °C for at least two consecutive years. Around a quarter of the northern hemisphere land surface is underlain by it.

What is the active layer?

The active layer is the surface layer that thaws each summer and refreezes each winter. Depth ranges from a few centimetres to about 4 m.

Why does the active layer become waterlogged in summer?

Frozen ground beneath the active layer is impermeable, so meltwater cannot drain downward. The thawed surface becomes saturated and mobile.

Define a periglacial environment.

A periglacial environment is a cold region beyond the ice margin where frost processes dominate. Permafrost and a seasonally thawing active layer are its defining features.

An ice lens is a horizontal body of segregated ice within the soil. Water is drawn towards the freezing front by capillary action and adds to the lens.

Eduqas A-Level Geography A110QS

Coastal LandscapesLandscape

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Glaciated Landscapes

Periglacial ground ice and permafrost features

2 things to know
Component 1 Section A

Overview

Active layer, periglacial environment and ice lens.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Define permafrost.

Key term

Distinguish continuous, discontinuous and sporadic permafrost.

Questions from this subtopic

Each one with the model answer underneath.

1
Define permafrost.
Model answer
Permafrost is ground that stays at or below 0 °C for at least two consecutive years. Around a quarter of the northern hemisphere land surface is underlain by it.
2
Distinguish continuous, discontinuous and sporadic permafrost.
Model answer
Continuous permafrost underlies over 90% of the surface in the coldest areas and can be 1,500 m thick in Siberia. Discontinuous permafrost has thawed patches and sporadic permafrost survives only in isolated pockets.
3
What is the active layer?
Model answer
The active layer is the surface layer that thaws each summer and refreezes each winter. Depth ranges from a few centimetres to about 4 m.
4
Why does the active layer become waterlogged in summer?
Model answer
Frozen ground beneath the active layer is impermeable, so meltwater cannot drain downward. The thawed surface becomes saturated and mobile.
5
Define a periglacial environment.
Model answer
A periglacial environment is a cold region beyond the ice margin where frost processes dominate. Permafrost and a seasonally thawing active layer are its defining features.
6
What is an ice lens?
Model answer
An ice lens is a horizontal body of segregated ice within the soil. Water is drawn towards the freezing front by capillary action and adds to the lens.

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Periglacial ground ice and permafrost features

Overview

What you need to know

Define permafrost.

Distinguish continuous, discontinuous and sporadic permafrost.

Questions from this subtopic

Define permafrost.

Distinguish continuous, discontinuous and sporadic permafrost.

What is the active layer?

Why does the active layer become waterlogged in summer?

Define a periglacial environment.

What is an ice lens?

Other ways to work this

What is inside Levo

The 3-step method, run for you

Cram a whole paper in one sitting

Blank Blitz makes facts automatic

Build It gets the exam shape right

Test It catches misconceptions

Brain Breaks between sessions

Every question in Glaciated Landscapes, on a schedule.