25 " H x 25" W
Embroidery on silk and velvet
The portion of the soil above permafrost that thaws and freezes seasonally is the active layer.
It plays an important role in cold regions because most ecological, hydrological, biogeochemical and soil forming activity takes place within it. Changes in active layer thickness are influenced by many factors including surface temperature, physical and thermal properties of the surface cover and substrate, vegetation, soil moisture and duration and thickness of snow cover.
A graphic representation of permafrost physics is here: https://graphics.reuters.com/CLIMATE-CHANGE/PERMAFROST/oakveelglvr/