Unit 5 Definitions Flashcards
Periglacial
A landscape that undergoes seasonal freezing and thawing, on the fringes of past and present glaciated regions.
Permafrost
Ground that remains frozen for two or more years.
Talik
Unfrozen ground between permafrost.
Active Layer
The surface level of soil which thaws in summer, and freezes in winter.
Ice wedge
A downward narrowing lens of ice, growing up to 3 metres wide at the surface, extending up to 10 metres below ground surface.
Frost Heave
A form of frost action, a physical weathering process involving freezing and thawing of water in soil or rock.
Stone sorted polygon
A type of patterned ground on low slopes, where stones are moved across the ground surface by freeze thaw action.
Open system pingo
A pingo formed by the doming of frozen ground, caused by groundwater that moves downslope through taliks, and onto pingo surfaces, where it freezes.
Closed system pingo
Pingo formed by doming of frozen ground due to freezing of injected water supplied by expansion of pore water during aggradation or permafrost.
Blockfields
Surfaces covered by large, angular rocks - a product of freeze thaw weathering on flat plateau surfaces.
Scree slope
Large rocks broken off by sediment, scree building up at the bottom of many inland cliffs.
Protalus Ramparts
A ramp shaped mound of scree that forms in a similar way to scree slopes. Differs in formation, as it involved ice or snow being present.
Solifluction Lobe
Saturated soil flowing under the influence of gravity.
Terracettes
Landforms consisting of a hillside ridge arranged as sub-parallel step like sequences.
Dry Valley
A valley in chalk or karst, with no permanent watercourse.
