1
Q
Ice wedges.
A
- 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.
2
Q
Pingo.
A
- 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.
3
Q
Stone polygons.
A
- 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.
