Ice-cored, dome-shaped hill, oval in plan, standing 2–50 m high, and 30–600 m in diameter, developed in an area of permafrost. The larger examples have breached crests in which ice may be exposed. They are probably due to local freezing of water that has migrated from adjacent uplands, or to the late freezing of the ground beneath a lake. See also palsa.
1 open system pingo, hydrostatic pingo A large ice mound formed under periglacial conditions, so called because it is formed from an unfrozen pocket confined by approaching permafrost. Mackay (1979) Geographie physique et quaternaire 33 argues that open system pingoes develop on former lakes.
2 closed system pingo An ice mound, as above, but formed as water, under artesian pressure within or below permafrost, which causes it to buckle upwards. MacKay (op. cit.) argues that not all such pingoes form in a truly closed system. Gurney (1998) PPG 22, 3 proposes a third category: polygenetic (or ‘mixed’) pingoes.
Pingo
- Trotsky, Leon (1879–1940)
- Trotter, Catherine
- troubadour
- Troubled Asset Relief Program
- trouble shooting
- trouble-shooting
- trough
- trough cross-stratification
- trout
- Trouton’s rule
- trowal
- Troy
- TRP protein
- TRS
- TR switch
- Trucial States
- Truck Acts
- Trudeau, Pierre (1919–2000)
- true age
- true and fair view
- true anomaly
- TrueColor
- true complement
- true dip
- true equator