The following figure illustrates a cross-section permafrost.

• At different latitudes, the active layer can thaw during summer and refreezes during winter. 1 mark
• The active season is shorter with increasing latitudes.

OR

• The active season is longer at decreasing latitudes. 1 mark

Award 1 for each challenge that is identified and 1 for further development/exemplification_.

Challenges include:

• the action of solifluction
• thermokarst/subsidence heat from buildings
• heat from pipelines
• changes in vegetation cover
• frost heave
• the weight of vehicles
• keeping cold water flowing to towns
• accessibility of settlements

Accept other valid challenge and explanation.