Periglacial landforms.

Question 1

Ice wedges.

Answer 1

• In winter, the active layer freezes and the soil layer contracts and forms natural polygonal patterns.
• The following summer, the cracks may close up or sometimes become filled with meltwater.
• In the subsequent winter, any water filled cracks expand as ice forms and the cracks widen to form ice wedges.
• Repeated freezing and thawing leads to wedges a metre wide and up to three metres deep.

Question 2

Pingo.

Answer 2

• They often form on the sites of small lakes.
• As these lakes fill with sediments from meltwater, the surrounding permafrost advances and squeezes the unfrozen sediments below the lake.
• When the lake itself is frozen, the water in the underlying sediments causes the surface to dome upwards creating the pingo.
• If the dome cracks, the ice core may melt leading to a collapse of the pingo and a pond forming in the central crater.

Question 3

Stone polygons.

Answer 3

• Mixture of fine grain material with larger stones.
• Cold penetrates the stones faster than the surrounding material.
• Freezing the ground beneath them.
• Forces them to rise above the rest of the material.
• Creating a stone polygon shape.
• On a hill- stones fall into stone stripes.