The active layer above the permafrost — the zone that thaws seasonally — is exactly the zone of most intense freeze-thaw cycling, and thus of most intense destruction of biological materials.

Human remains buried in the active layer are among the most vulnerable to this destructive process.

Cave environments, like the Trail Creek Caves, provide some protection from the most extreme freeze-thaw cycling.

The rock itself moderates temperature fluctuations inside the cave, and the alkaline chemistry of cave sediments in limestone or volcanic rock areas can inhibit some of the microbial and chemical processes that degrade organic materials.

This is one reason why cave sites are disproportionately important in the early human record of the Arctic — they represent a subset of the landscape where preservation conditions are more favorable than in most open-air contexts.