active layer

American  

noun

1. (in Arctic or subarctic regions) the layer of soil, above the permafrost, that thaws during the summer.

---

Example Sentences

When electricity passes through, electrons and holes recombine inside the active layer.

From Science Daily • Mar. 4, 2026

Over time, the active layer -- a layer of soil that freezes in winter and thaws in the summer -- thins.

From Science Daily • Oct. 11, 2023

Permafrost still covers 85 percent of the state, but “almost everywhere, the depth of the active layer is increasing over the last few decades,” said Thoman.

From Slate • Mar. 11, 2015

Increased phase separation and crystallization have a profound effect on the photophysical and transport properties of the active layer.

From Nature • Aug. 15, 2012

Because the frozen permafrost was just a half meter beneath the active layer of soil, all the water on the tundra stayed near the surface.

From "Two Degrees" by Alan Gratz