crystosphene
noun
crys·to·sphene
ˈkristəˌsfēn
plural -s
: a buried sheet of ice under the tundra of northern America formed by the freezing of spring water which rises from the rock beneath alluvial deposits or under swamps and spreads laterally at the zone of freezing
Word History
Etymology
cryst- (irregular from Greek krystallos ice) + -o- + Greek sphēn wedge