permafrost
CEFR: C1
A thick, subsurface layer of soil or sediment that remains continuously frozen at or below zero Celsius for years.
Synonyms
- cryotic ground
- permanently frozen subsoil
Common Collocations
- thawing permafrost
- melting permafrost
- permafrost layer
Example Sentence
Accelerated Arctic warming threatens to thaw deep permafrost, releasing gigatons of trapped methane.