active layer

American  

noun

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

---

Example Sentences

The active layer holds large quantities of organic material that have been frozen for thousands of years.

From Science Daily • Apr. 4, 2026

In aspect ratio phase trapping, defects, as well as the undesirable hexagonal phase, are "trapped" inside the grooves so that the surface of the active layer is a perfect cubic-phase material.

From Science Daily • Jan. 23, 2024

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

This sequence of steps is affected by the morphology 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