Definition of active layer in English:

active layer

noun

Geography
  • The seasonally thawed surface layer above permafrost.

    • ‘In streams of both regions, flows peak rapidly for several days as snow and ice melt in late May; then, stream discharge attenuates slowly as the active layer thaws.’
    • ‘A bear can dig an entrance in a peat bank up to 120 cm deep by digging through the active layer into the permafrost and then digging to excavate the main body of the den.’
    • ‘This allows water to change to freeze and thaw seasonally, creating stresses within the active layer that may lead to sorting of stones of different sizes within the substrate, to the formation of ‘patterned ground’.’
    • ‘The larger and larger trees indicate that the active layer, which thaws each summer, is deeper and deeper, giving roots of large trees room to grow down.’
    • ‘Consequently, during the summer growing season the active layer of the soil horizon will normally be aerated.’