| ablation till | A general term for loose, relatively permeable, earthy material deposited during the downwasting of nearly static glacial ice, either contained within or accumulated on the surface of the glacier.... |
| accretion [sedimentology] | The gradual increase or extension of land by natural forces acting over a long period of time, as on a beach by the washing up of sand from the sea or on a flood plain by the accumulation of sedim... |
| active layer | The top layer of ground subject to annual thawing and freezing in areas underlain by permafrost. nrc |
| alluvial cone | A semi-conical type of alluvial fan with very steep slopes; it is higher, narrower, and steeper (e.g., > 40% slopes) than a fan, and composed of coarser, and thicker layers of material deposited b... |
| alluvial fan | - A low, outspread mass of loose materials and/or rock material, commonly with gentle slopes, shaped like an open fan or a segment of a cone, deposited by a stream (best expressed in semiarid re...
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| alluvial flat | (a) (colloquial: western u.s.a.) a nearly level, graded, alluvial surface in bolsons and semibolsons that lacks distinct channels, terraces, or flood plain levels. |
| alluvial plain | (a) a large assemblage of fluvial landforms (braided streams, terraces, etc.,) that form low gradient, regional ramps along the flanks of mountains and extend great distances from their sources (e... |
| alluvial plain remnant | An erosional remnant of an alluvial plain which retains the surface form and alluvial deposits of its origin but was not emplaced by, and commonly does not grade to a present-day stream or drainag... |
| alpine - (a) [geomorphology] | (adjective) characteristic of, or resembling the european alps, or any lofty mountain or mountain system, especially one so modified by intense glacial erosion as to contain cirques, horns, etc. (... |
| alpine glacier | A) any glacier in a mountain range except an ice cap or ice sheet. it usually originates in a cirque and may flow down into a valley previously carved by a stream. compare - continental glacier. g... |
| annular drainage pattern | A drainage pattern in which subsequent streams follow a roughly circular or concentric path along a belt of weak rocks, resembling in plan view, a ring-like pattern where the bedrock joints or fra... |
| anthropogenic feature | An artificial feature on the earth’s surface (including those in shallow water), having a characteristic shape and range in composition, composed of unconsolidated earthy, organic materials, artif... |
| arete | A narrow, jagged mountain crest, often above the snowline, sculptured by alpine glaciers and formed by backward erosion of adjoining cirque walls. hp |
| artificial collapsed depression | A collapse basin, commonly a closed depression, which is the direct result of surficial subsidence associated with subsurface mining (e.g., long-wall mining). sw. |
| artificial drainage pattern | Human-made networks of drainage structures (ditches, canals, etc.) built primarily to lower or control the local water table in low lying, flat topography such as glacial lakebeds, broad flood pla... |
| artificial levee | An artificial embankment constructed along the bank of a watercourse or an arm of the sea, to protect land from inundation or to confine streamflow to its channel. gg |
| ash [volcanic] | Unconsolidated, pyroclastic material less than 2 mm in all dimensions. commonly called "volcanic ash” compare - block [volcanic], cinders, lapilli, tephra. sw & kst |
| ash flow - (not preferred | See pyroclastic flow, pyroclastic surge) a highly heated mixture of volcanic gases and ash, traveling down the flank of a volcano or along the surface of the ground; produced by the explosive disi... |
| avalanche chute | [preferred term] the central, channel-like corridor, scar, or depression along which an avalanche has moved. an eroded surface marked by pits, scratches, and grooves. gg |
| avalanche track | (not recommended as a landform term - use avalanche chute). the path formed by an avalanche. it may take the form of an open path in a forest, with bent and broken trees, or an eroded surface mark... |
| axial stream | (a) the main stream of an intermontane valley, flowing in the deepest part of the valley and parallel to its longest dimension. (b) a stream that follows the axis of a syncline or anticline. gg |
| b) (not preferred | Refer to u-shaped valley): (relict) - landforms or sediments formed, modified or deposited by a glacier in or on mountains or high hills that has since melted away. compare - glacial-valley floor,... |
| back-barrier beach | A narrow, elongate, intertidal, sloping landform that is generally parallel with the shoreline located on the lagoon or estuary side of the barrier island, or spit. compare - barrier island. sss |
| back-barrier flat | A subaerial, gently sloping landform on the lagoon side of the barrier beach ridge composed predominantly of sand washed over or through the beach ridge during tidal surges; a portion of a barrier... |
| bar [microfeature] | A small, sinuous or arcuate, ridge-like lineation on a flood plain and separated from others by small channels or troughs; caused by fluvial processes and common to flood plains and young alluvial... |
| bar and channel topography | A local-scale topographic pattern of recurring, small, sinuous or arcuate ridges separated by shallow troughs irregularly spaced across low-relief flood plains(slopes generally 2 -6 %); the effect... |
| barchan dune | A crescent-shaped dune with tips extending leeward (downwind), making this side concave and the windward (upwind) side convex. barchan dunes tend to be arranged in chains extending in the dominant... |
| barrier beach | (a) a narrow, elongate, coarse-textured, intertidal, sloping landform that is generally parallel with the beach ridge component of a barrier island or spit and adjacent to the ocean. compare - bar... |
| barrier cove | A subaqueous area adjacent to a barrier island or submerged barrier beach that forms a minor embayment or cove within the larger basin. compare - cove, mainland cove. sss |
| barrier flat | A relatively flat, low-lying area, commonly including pools of water, separating the exposed or seaward edge of a barrier beach or barrier island from the lagoon behind it. an assemblage of both d... |
| barrier island | A long, narrow, sandy island, that is above high tide and parallel to the shore that commonly has dunes, vegetated zones, and swampy or marshy terrains extending lagoonward from the beach. compare... |
| basal till | (a) (not preferred; obsolete) refer to subglacial till. unconsolidated material of mixed composition deposited at the base (bottom) of a glacier [ the term emphasizes only the relative position of... |
| base level | The theoretical limit or lowest level toward which erosion of the earth`s surface constantly progresses but seldom, if ever, reaches; especially the level below which a stream cannot erode its bed... |
| base slope [geomorphology] | A geomorphic component of hills consisting of the concave to linear slope (perpendicular to the contour) which, regardless of the lateral shape is an area that forms an apron or wedge at the botto... |
| basin floor | A general term for the nearly level, lower-most part of intermontane basins (i.e. bolsons, semibolsons). the floor includes all of the alluvial, eolian, and erosional landforms below the piedmont ... |
| basin-floor remnant | (colloquial: western u.s.a.) a relatively flat, erosional remnant of any former landform of a basin floor that has been dissected following the incision of an axial stream. ffp |
| bay bottom | The nearly level or slightly undulating central portion of a submerged, low-energy, depositional estuarine embayment characterized by relatively deep water (1.0 to >2.5 m). compare - lagoon bottom... |
| beach plain | A continuous and level or undulating area formed by closely spaced successive embankments of wave-deposited beach material added more or less uniformly to a prograding shoreline, such as to a grow... |
| beach ridge | A low, essentially continuous mound of beach or beach-and-dune material heaped up by the action of waves and currents on the backshore of a beach, beyond the present limit of storm waves or the re... |
| beach sands [soil survey] | Well sorted, sand-sized, clastic material transported and deposited primarily by wave action and deposited in a shore environment. compare - eolian sands. sw |
| beach terrace | (a) a landform that consists of a wave-cut scarp and wave-built terrace of well-sorted sand and gravel of marine and lacustrine origin. (b) (colloquial: western u.s.a.) relict shorelines from pluv... |
| beaded stream pattern | A characteristic pattern of small streams in areas underlain by ice wedges. the course of the stream channel is controlled by the pattern of the wedges, with beads (pools) occurring at the junctio... |
| bed [stratigraphy] | The layer of sediments or sedimentary rocks bounded above and below by more or less well-defined bedding surfaces. the smallest, formal lithostratigraphic unit of sedimentary rocks. the designatio... |
| beveled base | The lower portion of a canyon wall or escarpment marked by a sharp reduction in slope gradient from the precipitous cliff above, and characteristically composed of thinly mantled colluvium (e.g. <... |
| beveled cut | A bank or slope portion of a cut excavated into unconsolidated material (regolith) or bedrock as in a roadcut, whose slope gradient has been mechanically reduced to a subdued angle (e.g. to < 33 %... |
| blind valley | A valley, commonly in karst, that ends abruptly downstream at the point at which its stream disappears underground. gg |
| block [volcanic] | A pyroclast that was ejected in a solid state; it has a diameter greater than 64 mm. |
| block field | A thin accumulation of stone blocks, typically angular, with only coarse fragments in the upper part, over solid or weathered bedrock, colluvium, or alluvium, without a cliff or ledge above as an ... |
| block glide [mass movement] | The process, associated sediments (block glide deposit) or resultant landform characterized by a slow type of slide, in which largely intact units (blocks) of rock or soil slide downslope along a ... |
| block lava | Lava having a surface of angular blocks; it is similar to `a`a lava but the fragments are larger and more regular in shape, somewhat smoother, and less vesicular. compare - `a`a lava, pahoehoe lav... |
| block lava flow | A lava flow dominated by block lava. compare -`a`a lava flow, pahoehoe lava flow, pillow lava flow. sw |
| block stream | An accumulation of boulders or angular blocks, with no fine sizes in the upper part, overlying solid or weathered bedrock, colluvium, or alluvium, and lying below a cliff or ledge from which coars... |
| blue rock [volcanic] - (colloquial | Hawaii) the very dense (e.g. 2.75 g/cc), extremely hard and massive, nominally vesicular lava that commonly forms the inner core of an `a`a lava flow. sw |
| bolson | (colloquial: western usa.) a term applied to an internally drained (closed) intermontane basin in arid regions where drainages from adjacent mountains converge toward a central depression. bolsons... больсон; |
| bomb [volcanic] | A pyroclast > 64 mm in at least one dimension that was ejected while still viscous and solidified into it’s rounded form in flight. compare - block, cinder, lapilli, tephra. gg |
| boulder field | (not recommended) use block stream. compare - block field. |
| bowl [gilgai] | A cup-or trough-shaped subsurface feature centered under and surrounding the micro-low of a gilgai, commonly 3-5 m across and 1.5-3 m thick, containing numerous slickensides (oblique slip / shear ... |
| braided stream | A channel or stream with multiple channels that interweave as a result of repeated bifurcation and convergence of flow around inter-channel bars, resembling (in plan view) the strands of a complex... |
| broad interstream divide | - (colloquial: southeastern usa) a type of very wide, low gradient (level to nearly level) interfluve that lacks a well developed drainage network such that large portions of the local upland la...
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| brook [streams] | (not preferred, refer to ephemeral stream) generally a very small, ephemeral stream, especially one that issues from a spring or seep and conducts less water volume and over shorter distances than... |
| burial mound | A small human-made hill, composed of debris accumulated during successive occupations of the site, or of earth heaped up to mark a burial site; also called mound. gg |
| buried soil | Soil covered by an alluvial, loessal, or other earthy mantle of more recent material, typically to depths exceeding 50 cm; recent surface deposits < 50 cm thick are generally considered as part of... |
| canyon bench | One of a series of relatively narrow, flat landforms occurring along a canyon wall and caused by differential erosion of alternating strong and weak horizontal strata; a type of structural bench. ... |
| canyonlands | A deeply and extensively dissected landscape composed predominantly of relatively narrow, steep-walled valleys with small flood plains or valley floors; commonly with considerable outcrops of hard... |
| caprock | - A) a hard rock layer, usually sandstone, lava or in arid environments, limestone, that lies above shale or other less resistant bedrock or sediments; specifically a rock layer that forms relat...
вскрыша; |
| captured stream | A stream whose course has been diverted into the channel of another stream by natural processes. gg |
| carolina bay | Any of various shallow, often oval or elliptical, generally marshy, closed depressions in the atlantic coastal plain (from southern new jersey to northeastern florida, especially developed in the ... |
| cat clay - (not recommended | Obsolete) wet, clay dominated soils containing ferrous sulfide which become highly acidic when drained. gsst |
| catsteps | (not preferred, refer to terracettes). a terracette; especially one produced by slumping of loess deposits as in western iowa. gg |
| centripetal drainage pattern | A drainage pattern in which the streams converge inward toward a central depression; generally indicative of a structural basin, volcanic crater, caldera, breached dome, bolson, or the end of an e... |
| chenier plain | A mud-rich strand plain, occupied by cheniers and intervening mud-flats with marsh and swamp vegetation. compare - chenier, strand plain. gg |
| chimney [gilgai] | A subsurface feature that forms a crude cone or wave-crest structure centered under a micro-high (e.g. a low mound or rim) and extending at least part-way under adjacent intermediate positions, co... |
| cinders | Uncemented vitric, vesicular, pyroclastic material, more than 2.0 mm in at least one dimension, with an apparent specific gravity (including vesicles) of more than 1.0 and less than 2.0. compare -... |
| circular gilgai | A type of gilgai dominated by circular closed depressions (micro-lows) separated by low mounds (micro-highs); the prevailing type of gilgai on relatively level terrain (slopes < 3 %). distance fro... |
| cirque floor | The comparatively level bottom of a cirque, thinly mantled with till and consisting of glaciallyscoured knolls and hillocks separated by depressions, flat areas and small lakes (tarn); commonly it... |
| cirque headwall | The glacially-scoured, steep and arcuate side or wall of a cirque, dominated by rockoutcrops, rubble, and colluvium. compare - headwall. sw & hd |
| cirque platform | A relatively level or bench-like surface formed by the coalescence of several cirques. gg & sw |
