When scientists talk about the cryosphere, they mean the places on Earth where water is in its solid form, frozen into ice or snow. Read more ...
Cryosphere Glossary
crust
a hard snow surface lying upon a softer layer; crust may be formed by sun, rain or wind, and is described as breakable crust or unbreakable crust, depending upon whether it wil break under the weight of a turning skier.