Moraine (glacial geology) — An accumulation of drift, 

 with an initial topographic expression of its own, built 

 chiefly by the direct action of glacial ice. Examples are 

 end, ground, lateral, recessional, and terminal moraines. 

 (See glacial till.) HP 



Moraine end — A moraine produced at the front of an 

 actively flowing glacier at any given time. (See terminal 

 and recessional moraines.) HP 



Moraine (ground) — An extensive, fairly even and thin 

 layer of till, having an undulating surface; a deposit of 

 rock debris dragged along, in, on, and beneath a gla- 

 cier and emplaced by processes including basal lodge- 

 ment and release from downwasting stagnant ice (by 

 ablation), (fig. B-7) HP 



Moraine (lateral) — A ridge-like moraine carried on and 

 deposited at the side margin of a valley glacier. It is 

 composed chiefly of rock fragments derived from val- 

 ley walls by glacial abrasion and plucking, or mass- 

 wasting, (fig. B-7) HP 



Moraine (recessional) — An end moraine, built during a 

 temporary but significant halt in the final retreat of a 

 glacier. HP 



Moraine (terminal) — An end moraine that marks the 

 farthest advance of a glacier and usually has the form 

 of a massive arcuate ridge, or complex of ridges, under- 

 lain by till and other drift types, (fig. B-7) HP 



Mound — A low, rounded hill of earth, natural or artificial. 

 GG 



Mountain — A natural elevation of the land surface, rising 

 more than 1,000 ft (300 m) above surrounding lowlands, 

 usually of restricted summit area (relative to a plateau), 

 and generally having steep sides (>25% slope) with or 

 without considerable bare-rock surface. A mountain can 

 occur as a single, isolated mass, or in a group forming a 

 chain or range. Mountains are primarily formed by deep 

 seated earth movements and/or volcanic action and sec- 

 ondarily by differential erosion. (See hill.) HP 



Muck — Highly decomposed organic material in which 

 the original plant parts are not recognizable. Contains 

 more mineral matter and is usually darker in color than 

 peat. GSST 



Mudstone — Sedimentary rock formed by induration of 

 silt and clay in approximately equal proportions. 



Natural levee — A long broad low ridge or embankment 

 of sand and coarse silt, built up by a stream on its flood 

 plain and along both sides of its channel. They are 

 wedge-shaped deposits, of coarsest suspended-load 

 material, that slope gently away from the stream. (See 

 meander belt.) GG & HP 



Nivation — The process of excavation of a shallow depres- 

 sion or nivation hollow in the mountain side by removal 

 of fine material around the edge of a shrinking snow 

 patch or snow bank, chiefly through sheetwash, rivulet 

 flow, and solution in melt water. More generally, the 

 work of snow and ice beyond the limits of glacial 

 action. GG 



Nunatak — An isolated hill, knob, ridge, or peak of bed- 

 rock that projects prominently above the surface of a 

 glacier and is completely surrounded by glacier ice. 

 Nunataks are common along the coast of Greenland. 

 GG 



Outwash plain — An extensive lowland area forming the 

 surface of a body of coarse textured, glaciofluvial 

 material. An outwash plain is commonly smooth; 

 where pitted, due to melt-out of incorporated ice masses, 

 it is generally low in relief. (See glacial outwash and 

 kettles.) (fig. B-7) HP 



Outcrop — That part of a geologic formation or structure 

 that appears at the surface of the earth. GG 



Overthrust — A low angle thrust fault of large scale, with 

 displacement generally measured in kilometers. GG 



Oxbow — A closely looping stream meander having an 

 extreme curvature such that only a neck of land is left 

 between the two parts of the stream. A term used in 

 New England for the land enclosed, or partly enclosed, 

 within an oxbow. (See meander belt and oxbow lake.) 

 GG 



Oxbow lake — The crescent-shaped, often ephemeral, 

 body of standing water situated by the side of a stream 

 in the abandoned channel (oxbow) of a meander after 

 the stream formed a neck cutoff and the ends of the 

 original bend were silted up. (See meander belt and 

 oxbow.) GG 



Paleosol — A soil that formed on a landscape of the past 

 (Ruhe 1975) with distinctive morphological features 

 resulting from a soil-forming environment that no 

 longer exists at the site. The former pedogenic process 

 was either altered because of external environmental 

 change or interrupted by burial. A paleosol (or compo- 

 nent horizon) may be classed as relict if it has persisted 

 in a land-surface position without major alteration of 

 morphology by processes of the prevailing pedogenic 

 environment. An exhumed paleosol is one that for- 

 merly was buried and has been re-exposed by erosion 

 of the covering mantle. Most paleosols have been af- 

 fected by some modification of diagnostic-horizon 

 morphologies and profile truncation. HP 



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