Imnavait Creek Grid Surficial Geomorphology
- Imnavait Grid
- Releve Locations
- Glacial Geology
- Percent Water
- Surficial Geology
- Surficial Geomorphology
(from metadata) The Imnavait Creek grid map is near the center of the Upper Kuparuk River region map. The area contains surfaces with irregular topography that were glaciated during the Late Pleistocene.
The surfaces of the landscapes in the Imnavait Creek area have been modified by a variety of geomorphological processes including alluviation (movement of material by water), colluviation (movement of material by gravity), and periglacial processes (freezing and permafrost-related phenomena). Common surficial geomorphological features within the mapped area include sorted and nonsorted circles (frost boils), turf hummocks, gelifluction lobes and terraces, water tracks, high-and low-centered ice-wedge polygons, wetland features and thermokarst features.
Classes of surficial geomorphology:
- Stony surface: Areas covered by cobbles and stones such as river gravels, talus slopes, blockfields, and bedrock areas.
- Nonsorted circles: Roughly circular, 1-2-m diameter, slightly convex barren features, spaced from 2 to many meters apart. They are composed of fine-grained mineral material that periodically undergo freezing and heaving. Nonsorted circles, or frost scars, are ubiquitous features on most hillslopes, and are not differentiated here unless they cover more than 50% of a surface.
- Stripes: Hillslopes with a striped pattern consisting of elongated, relatively dry well-drained elements 1-3 m wide, oriented down the steepest available slope, alternating with intervening moister interstripe elements 1-3 m wide. They are caused by a combination of cryoturbation, erosion, and gelifluction. The dry elements usually are covered by nonsorted circles. Most stripes are nonsorted with similar grain size of material in the stripe and interstripe areas; sorted stripes and circles occur in rocky alpine areas.
- Upland turf hummocks: Small regularly spaced hummocks (<50 cm high), 25 to 50 cm wide, thought to be caused by a combination of runoff, thermal erosion and gelifluction. They are common on steep well-drained slopes, often found in association with snowbeds and gelifluction lobes and terraces.
- Gelifluction features: Areas of slow downslope movement of the active layer caused by saturated soils moving over permanently frozen ground. Includes gelifluction lobes, benches, and streams mostly greater than 50 cm high. Common on steep hillslopes.
- Well-developed hillslope watertracks: Shallow subparallel drainages normally spaced tens of meters apart, with well defined channels giving many slopes distinctive "horsetail" patterns. Well-developed watertracks carry runoff and meltwater through most of the summer and are usually filled with shrubby vegetation. They are most abundant on long lower hillslopes, particularly slopes that have deep snow accumulation to provide meltwater throughout the summer.
- Poorly-developed hillslope watertracks: Watertracks with poorly defined channels that normally carry runoff only during the snowmelt season and immediately after rainfall events. They are discernible on aerial photographs because of somewhat shrubbier vegetation in the water tracks. Poorly defined watertracks often occur on upper hillslopes and may turn into well-developed watertracks on the lower slopes.
- Low-centered ice-wedge polygons: Ice-wedge polygons composed of a central low "basin", a raised "rim", and a "trough" between polygons. The basins are usually 8-10 m in width and circular to weakly polygonal in plan. The raised rims of the polygons may be as much as 1-2 m wide, as much as 0.5 m higher than the basin and may compose over 30% of the total polygonal unit. The troughs of polygons occur over the tops of underlying ice wedges, and are usually less than 1 m wide. The basins and troughs are usually wet all summer. Thermokarst ponds commonly occur at the junctions of polygon troughs. Low-centered polygons are not abundant in the region but occur in association with flat drained lake basins and river floodplains. pads.
- High-centered ice-wedge polygons and palsas: Ice-wedge polygons with a center portion that is raised above the trough element. Relief between the center and the trough is normally about 0.5-1.0 m, and polygon diameters are usually 10-15 m in diameter. High centered polygons occur marginal to larger streams and rivers, especially on outwash terraces. On some upland surfaces, the polygons are poorly developed or totally masked by tussock-tundra vegetation. Some raised features, particularly in colluvial palsas, which are small peaty mounds with perennial ice lenses.
- Wetland microrelief: Wet areas with a mixture of strangmoor, disjunct ice-wedge polygon rims, aligned hummocks, nonaligned hummocks, and lowland watertracks. Strangmoor consists of strangs, which are sinuous ridges many meters long that form perpendicular to the direction of the local hydrologic gradient. Aligned hummocks are shorter features also oriented perpendicularly to the hydrologic gradient. The strangs are up to 0.5 m wide and 0.5 high. Disjunct polygon rims are associated with incompletely formed or eroded low-centered polygons.
- Thermokarst: This code is used in three situations:
- (1) Areas with eroding subsurface ice that may be buried glacial ice or ice-rich permafrost; this occurs marginal to several kettle lakes on Itkillik-age glacial surfaces.
- (2) Thermokarst pits that occur at ice-wedge junctions and often associated with ice-wedge polygons.
- (3) Beaded streams with regularly spaced circular pools that have formed where the stream has eroded out ice-wedge junctions; between "beads" the stream often follows a linear channel along eroded ice-wedges.
- Pond complex: Wetland areas with numerous ponds mixed with relatively well-drained areas.
- Featureless: Areas with no discernible pattern at the mapping scale. However, nonsorted circles, small gelifluction features, and/or poorly-developed water tracks commonly occur in these areas.
- Irregular microrelief: This unit is used for a wide variety of situations where there is considerable microrelief that cannot be ascribed to any of the above features, such as rolling topography common on till and outwash surfaces, hillslopes and bluffs with irregular erosion features, and floodplains with a mixture of channels, bars, ponds, etc.
- Water: Includes lakes, ponds, and rivers.
- Disturbed: Includes gravel mines and contstruction pads.