Accumulations of snow which do not flow, found mainly at high latitudes or altitudes, often in sunless situations like shady gorges or avalanche corridors, persistent within the limits of permanent snow but elsewhere susceptible to melting in hot summers, especially if the preceding snowfalls have been light. Some bryophytes can survive in such a habitat, an abundance of unicellular algae can colour the snow and certain insects feed on material released by melting.

[This habitat could not be formally defined in the expert system because it is not based on vegetation.]