ficial) and deposits the coarser part of its load on the 

 adjacent flood plain. (See meander belt.) HP 

 Floor— -A generic term for the nearly level, lower part of 

 a basin or valley, the bed of any body of water, for 

 example, the nearly level surface beneath the water of a 

 stream, lake, or ocean. 



Flow (mass move) — A mass movement of unconsolidated 

 material that exhibits a continuity of motion and a 

 plastic or semifluid behavior resembling that of a vis- 

 cous fluid; for example, creep, solifluction, earthflow, 

 mudflow, debris flow, and sturzstrom. The mass of 

 material moved by a flow. GG 



Fluvial— Of or pertaining to rivers; produced by river 

 action, such as a fluvial plain. HP 



Fold — A curve or bend of a plenar structure such as rock 

 strata, bedding planes, foliation, or cleavage. GG 



Foothills — A steeply sloping upland with hill relief (up to 

 1 ,000 ft (300 m)) that fringes a mountain range or high- 

 plateau escarpment. (See hill, mountain, and plateau.) 

 HP 



Footslope — The geomorphic component that forms the 

 inner gently inclined surface at the base of a hillslope. 

 The surface profile is dominantly concave; and in 

 terms of gradational processes, it is a transition zone 

 between upslope sites of erosion (backslope) and 

 downslope sites of deposition (toeslope). (See 

 hillslope.) (fig. B-2) HP 



Foredune — A coastal dune or dune ridge oriented parallel 

 to the shoreline, occurring at the landward margin of 

 the beach, along the shoreward face of a beach ridge, 

 or at the landward limit of the highest tide, and more 

 or less completely stabilized by vegetation. GG 



Formation (stratigraphy) — The basic rock-stratigraphic 

 unit in the local classification of rocks. A body of rock 

 (commonly a sedimentary stratum or strata, but also 

 igneous and metamorphic rocks) generally character- 

 ized by some degree of internal lithologic homogeneity 

 or distinctive lithologic features (such as chemical com- 

 position, structures, textures, or general kind of fos- 

 sils), by a prevailing (but not necessarily tabular) 

 shape, and by mappability at the earth's surface (at 

 scales of the order of 1:25.000) or traceability in the 

 subsurface. HP 



Frost churning — A collective term suggested by Bryan 

 (1946, p. 640) to describe the stirring, churning, modi- 

 fication, and all other disturbances of regolith, and 

 other earth materials resulting from frost action. It 

 involves frost heaving, solifluction, and differential 

 and mass movements, and it produces patterned ground. 



Synonyms for frost churning are congeliturbation, 

 cryoturbation, and frost stirring. GG 



Frost riving — (See frost shattering.) 



Frost shattering — The mechanical disintegration, splitting, 

 or breakup of a rock or soil caused by the great pres- 

 sure exerted by the freezing of water contained in cracks 

 or pores, or along bedding planes; (Bryan 1946, p. 640). 

 Synonyms for frost shattering include congelifraction, 

 frost splitting, frost riving, frost bursting, frost weath- 

 ering, frost wedging, gelivation, and gelifraction. GG 



Geomorphic surface — A geomorphic surface represents 

 an episode of landscape development and consists of 

 one or more landforms (Balster and Parsons 1968). A 

 mappable part of the land surface that is defined in 

 terms of morphology (relief, slope, aspect, and the 

 like), age (absolute, relative), and stability of compo- 

 nent landforms. (See buried, exhumed, and relict.) HP 



Gilgai — The microrelief of soils produced by expansion 

 and contraction with changes in moisture. Found in 

 soils that contain large amounts of clay which swells 

 and shrinks considerably with wetting and drying. 

 Usually a succession of microbasins and microknolls in 

 nearly level areas or of microvalleys and microridges 

 parallel to the direction of the slope. GSST 



Glacial — Of or relating to the presence and activities of 

 ice and glaciers, as glacial erosion. Pertaining to dis- 

 tinctive features and materials produced by or derived 

 from glaciers and ice sheets, as glacial lakes. Pertaining 

 to an ice age or region of glaciation. GG 



Glaciation — The formation, movement, and recession of 

 glaciers or ice sheets. A collective term for the geologic 

 processes of glacial activity, including erosion and dep- 

 osition, and the resulting effects of such action on the 

 earths surface. GG 



Glacial drift— (See drift.) 



Glacial marine — Marine sediments that contain glacial 

 material. A synonym for glacial marine is glaciomarine. 

 GG 



Glaciomarine — (See Glacial marine.) GG 



Glacial outwash — Stratified sand and gravel produced by 

 glaciers and carried, sorted, and deposited by water 

 that originated mainly from the melting of glacial ice. 

 Outwash deposits may occur in the form of valley fills 

 (valley trains and/or outwash terraces) or as widespread 

 outwash plains. (See glacial drift and glaciofluvial 

 deposits.) HP 



Glacial till — Unsorted and unstratified glacial drift, gen- 

 erally unconsolidated, deposited directly by a glacier 

 without subsequent reworking by water from the gla- 

 cier, and consisting of heterogeneous mixture of clay, 



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