Frost Mounds Research Articles

Advances in Periglacial Geomorphology

Nivation: A Geomorphic Chimera Recent Advances in Cryogenic Weathering Cryoplanation Rock Glaciers Stratified Slope Deposits Ground Ice and Permafrost Active Layer Processes Cryoturbations Seasonal Frost Mounds Earth Hummocks Palsas and Related Forms Pingos: An Overview of the Present State of Knowledge Pingo Scars and their Identification Slope Processes An Alpine Periglacial Zone Periglacial Hydrology A Periglacial Overview.

Ground ice on Svalbard

Abstract Svalbard is an area of widespread occurrence not only of glaciers but also of ground ice. Field studies conducted in 1987 for the first time provided data on the structure and occurrence of ground ice, from ice cement and segregated ice to massive ice bodies, including buried glacier ice and snowpatch ice, as well as segregated and injected ice in frost mounds and thermokarst cavity ice. Ice cement is the most widespread type of primary ground ice; secondary ice includes vein ice; and buried ice includes buried glacier ice and buried snowpatch ice. The article presents details of the differing characteristics of the ice in each category.

Frost Mounds Formed by Degradation at Slope Mountain, Alaska, U.S.A.

Stable, ice-cored frost mounds can form by differential ablation of seasonally developed massive ground ice. Although degradation frost mounds have no diagnostic mound morphology, these features can be identified by observing formative processes in the field and by examination of the mound core. Several field techniques were employed on massive ice-cored mounds which developed in a marsh near Slope Mountain, Alaska. Stratigraphic relationships within the mound core, ice petrofabrics, and ionic concentration patterns of ice crystals as they vary with core depth were correlated to the mound-forming processes, and indicate that these landforms are stable remnants of a sill-like massive ground ice plateau which has been differentially eroded by stream action. In addition, the core data and field observation can be used to infer the processes associated with massive ground-ice formation. It appears that a 1-m-thick, massive ice plateau develops in the marsh each winter due to the concordant injection and freez...

Frost Mounds Formed by Degradation at Slope Mountain, Alaska, U.S.A.

Frost Mounds Formed by Degradation at Slope Mountain, Alaska, U.S.A.

The Birth and Growth of Porsild Pingo, Tuktoyaktuk Peninsula, District of Mackenzie

The birth and growth of Porsild Pingo (ice-cored hill) can be taken as fairly representative of the birth and growth of the more than 2000 closed-system pingos of the western arctic coast of Canada and adjacent Alaska. Porsild Pingo, named after a distinguished arctic botanist, has grown in the bottom of a large lake that drained catastrophically about 1900. Porsild Pingo has grown up at the site of a former shallow residual pond. The "birth" probably took place between 1920 and 1930. The high pore water pressure that caused updoming of the bottom of the residual pond to give birth to Porsild Pingo came from pore water expulsion by downward and upward permafrost growth in saturated sands in a closed system. In the freeze-back period of October-November 1934, permafrost ruptured and the intrusion of water into the unfrozen part of the active layer grew a 3.7 m high frost mound photographed by Porsild in May 1935. Porsild Pingo has grown up at, or very close to, the site of the former frost mound. The growth of Porsild Pingo appears to have been fairly steady from 1935 to 1976, after which there has been a decline to 1987. The growth rate has been nearly linear with height, from zero at the periphery to a maximum at the top. The present addition of water to the pingo is about 630 cu m/y. Providing there is no major climatic change. Porsild Pingo may continue to grow for a few centuries.Key words: frost mound, intrusive ice, permafrost, pingo, Porsild

FROST MOUNDS AT TOOLIK LAKE, ALASKA

Aggradation palsas and seasonal frost mounds can achieve topographic expression by localized pooling and freezing of water within the active layer. A distinction is drawn in this paper between palsas, which are permafrost landforms by definition, and seasonal frost mounds, ephemeral or oscillatory features surviving for less than 2 years. Subsurface water migration occurs in response to positive or negative pore water pressures generated during active-layer refreezing. Upward deformation results from stresses induced by the local addition of water and subsequent phase change and, in some cases, positive pore water pressures. In the absence of site instrumentation, processes associated with mound formation can be inferred by examination of massive ice cores, where a record of the aggradational event is preserved. Stratigraphic and petrographic characteristics of the core, ionic concentration patterns with respect to depth, and mound morphometric data were obtained for a large ice-cored frost mound which de...

Positive forms of mesorelief as the result of ground ice formation

Abstract Positive forms of mesorelief in the north of Western Siberia, resulting from ice formation in frozen sediments, are analyzed. The role of cryogenic processes in their formation is evaluated. Three groups of frost mounds are distinguished, each resulting from different mechanisms. One category involves large, isolated mounds 20–30 m high with deep lakes around their bases and occasionally in their summits. A second type involves groups of mounds 5–10 m high forming elbow‐shaped or sickle‐shaped chains or ridges. And thirdly one encounters small mounds 3–4 m high, scattered in chaotic fashion over areas 1–2 km2 in area. Zonal and regional patterns in the distribution of all three types are discussed along with their morphological and cryological peculiarities.

A fossil frost mound of Late Dryas age in middle Jutland (Denmark)

Three to four km southwest of Egtved, in middle Jutland, diggings for a gas pipeline cut through a form which is believed to be a fossil frost mound. The horizontal outline of the form is that of a rounded silty body with a diameter of about 45 m. It is surrounded by layered eolian sand of which the layers are bent upwards into a vertical position close to the silty body. A small bulge of silty material is present on top of the neighbouring sand. The mechanism for the formation of the form is thought to have much in common with that of the hydrostatic system pingo of Mackay. It cannot be determined whether the mound was annual or perennial, but the presence of silty sediment in the central part shows that liquified sediment moved upward to fill the present form. By means of lithostratigraphy and pollen analysis, the development and decay of the mound were dated to Late Dryas time. It is suggested that similar features may be present in other parts of Scandinavia outside the area glaciated during the Late Dryas.

Groundwater hydraulics of seasonal frost mounds, North Fork Pass, Yukon Territory : Pollard, H W; French, H M Can J Earth Sci V21, N10, Oct 1984, P1073–1081

Groundwater hydraulics of seasonal frost mounds, North Fork Pass, Yukon Territory : Pollard, H W; French, H M Can J Earth Sci V21, N10, Oct 1984, P1073–1081

Diurnal Thermal Regime in a Peat-Covered Palsa, Toolik Lake, Alaska

Strong spatial and temporal variations in temperature and effective thermal diffusivity are apparent from short-term thermal records measured in the peat atop an ice-cored palsa in northern Alaska. Intersite differences in near-surface temperature regimes apparently result from topographic influences, vegetative cover, and site wetness. Values of effective thermal diffusivity indicate that ablation of the ice core is inhibited by advection of cold water near the ice-peat contact and by internal evaporation near the surface. These findings support the conclusions of earlier investigators, who emphasized the importance of peat for maintaining palsas near their equatorward limit. Key words: active layer, frost mound, palsa, peat, permafrost, soil temperature, thermal properties, Alaska

The Internal Structure and Ice Crystallography of Seasonal Frost Mounds

AbstractThe crystal character of the ice core within frost blisters supports the hypothesis that groundwater injection into residual zones of the active layer followed by rapid freezing is the primary growth mechanism for these features. The ice core is characterized by an upper zone of relatively small randomly arranged equigranular ice crystals which change with increasing depth to columnar anhedral crystals, commonly exceeding 200 mm in length, and with crystal diameters ranging between 25 and 35 mm. Petrofabric analyses show that the c-axis orientations are normal to crystal elongations, with crystal growth along the basal plane in an a-axis direction. These observations eliminate ice segregation as a possible growth mechanism, thereby distinguishing seasonal frost mounds from palsas.

The Internal Structure and Ice Crystallography of Seasonal Frost Mounds

AbstractThe crystal character of the ice core within frost blisters supports the hypothesis that groundwater injection into residual zones of the active layer followed by rapid freezing is the primary growth mechanism for these features. The ice core is characterized by an upper zone of relatively small randomly arranged equigranular ice crystals which change with increasing depth to columnar anhedral crystals, commonly exceeding 200 mm in length, and with crystal diameters ranging between 25 and 35 mm. Petrofabric analyses show that thec-axis orientations are normal to crystal elongations, with crystal growth along the basal plane in ana-axis direction. These observations eliminate ice segregation as a possible growth mechanism, thereby distinguishing seasonal frost mounds from palsas.

The groundwater hydraulics of seasonal frost mounds, North Fork Pass, Yukon Territory

Seasonal frost mounds occur in the North Fork Pass area in response to increased hydraulic potentials in perennial, spring-fed groundwater systems. Geochemical and isotope analyses indicate that local precipitation is the source of water for flow systems discharging from the springs. The direct measurement of pressure potentials in a number of frost blisters and icing blisters, undertaken in March 1982, gave values ranging from 30 and 81 kPa for mounds approximately 2.0 m high. These pressures exceed theoretical, calculated values and are attributed to the tensile strength of the soil and (or) ice overburden. In genetic terms, seasonal frost mounds should be clearly differentiated from other morphologically similar features such as palsas.

Frost Blisters of the Bear Rock Spring Area near Fort Norman, N.W.T.

Frost mounds of the frost blister type form every winter at the site of a group of cold mineralized springs on the east side of Bear Rock near Fort Norman, Northwest Territories, Canada. During each of four years of observation (1975-1978) three to five frost blisters formed, with measured heights ranging from 1.4 to 4.9 m, and with horizontal dimensions between 20 and 65 m. Locations of the blisters varied somewhat, presumably in response to differences in temperature regime and snow cover. Mature frost blisters consisted of a layer of frozen ground ... and a layer of ice ... covering a cavity which in some cases was over 4.0 m high. The cavities contained water during formation of the frost blisters; they were empty by spring. Time-lapse photography revealed that frost blisters can grow as fast as 0.55 m/d, and that some of them fracture, drain and partially subside one or more times before reaching their full height. During the summer, degradation occurs as a result of thawing and slumping of the soil cover and by melting and collapse of the ice layer; portions of the ice layer, or an uncollapsed section of a frost blister, can survive until the second summer after their formation. Water chemistry and isotope studies revealed that the frost blisters are formed by pressure build-up in subsurface water below seasonal frost and that the ice layers accumulate by gradual downward freezing in a closed (or intermittently opened) system filled with water derived from the Bear Rock spring system. Similar frost blisters are found in other areas of groundwater discharge in a variety of locations. Key words: frost blisters, hydraulic uplift, springs, icings, permafrost, environmental isotopes, time-lapse photography

Frost mounds at Bear Rock, near Fort Norman, Northwest Territories, 1975–1976

A number of frost mounds of the frost blister type were observed at the site of a group of cold springs on the east side of Bear Rock, about 4 km west-northwest of Fort Norman, Northwest Territories, Canada. The mounds ranged in height from 2.0 to 3.0 m, with horizontal dimensions between 26 and 48 m. They contained a domed layer of ice, up to 85 cm thick, over an empty cavity up to 70 cm high, which was in turn underlain by frozen ground. Soil cover over the ice layer was 30–65 cm thick. The ice presumably formed from springwater injected under considerable hydraulic potential. New frost blisters are formed annually. Three recent frost blisters observed in June 1975 were partially destroyed by melting, slumping of the soil cover, and collapse of the ice dome by mid-September 1975. A portion of the ice lasted into summer 1976. Three new frost blisters, formed during the 1975–1976 winter, were observed in March 1976; two of these had completely collapsed by mid-June. An icing blister associated with one of them ruptured on March 21, 1976, producing a large flow of water, which lasted for several hours. A section of the icing blister subsequently subsided. Remnants of frost blisters have been observed in a spring area northeast of Turton Lake, Northwest Territories, and along the Dempster Highway in North Fork Pass and near the crossing of Blackstone River, Yukon Territory.

Pingos and Pingo Scars: Their Characteristics, Distribution, and Utility in Reconstructing Former Permafrost Environments

Pingos are large frost mounds which develop in permafrost as the result of the segregation of massive ground-ice lenses. At least two genetic varieties of pingos, open- and closed-systems, form under differing conditions of climate, topography, and groundwater occurrence. Active pingos are known to occur in many high latitude regions. Pingo scars are the degeneration products of pingos. Ideally they are ramparted, circular depressions, although they may be expressed in a variety of divergent forms due to differing conditions of topography, substrate materials, degree of thermokarst overprint, and erosional/depositional histories. Pingo scars occur in many modern permafrost regions. Presumed pingo scars have also been identified in many regions beyond the present permafrost limit and therefore may have utility in reconstructing former permafrost environments.

GROUNDWATER DISCHARGE: A COMMON GENERATOR OF DIVERSE GEOLOGIC AND MORPHOLOGIC PHENOMENA

Abstract Four natural conditions co-exist inherently with the hydraulic discharge of groundwater: positive gradient of the fluid potential, low relative topographic position, allochthonous water quality, and allochthonous water temperature. In turn, these conditions are consistently associated with springs, seepages, quicksand, soap holes, geysers, frost mounds, pingos, groundwater lakes and marshes, and certain near-surface and surface accumulations of salts, landslides, slumps, soil creep and gullying, which is considered as an indication that these features have one common generator: groundwater discharge. The above geomorphic and geologic phenomena are, therefore, interpreted as environmentally modified expressions of the hydraulic discharge of groundwater through topographically controlled gravity flow systems.

A Type of Circular Lakes in Northernmost Norway

This paper supplements earlier reports on palsas and pingo-like frost mounds in northeasternmost Scandinavia (Fig. 1) and treats a form of circular to oval lakes having characteristics of both the palsa and the pingo form groups. The lakes differ from other lakes of regular shape by being enclosed by a low, uniform wall.The circular lakes are interpreted as a collapse stage of frost mounds, which may have originated as palsas or as pingos. Also, some localities with fossil circular forms have been observed, mostly situated at lower elevations.The climatic significance of the collapse features is briefly analyzed in comparison with that of the palsas. For the fossil, low-elevation rings, a climatological and temporal interpretation is advanced referring to radiocarbon dating and to the occurrence of fossil ice-wedge polygons in the area.

Pingos in the Yukon-Kuskokwim Delta, Alaska: Their Plant Succession and Use by Mink

Notes 1960-1963 investigations of these frost mounds, their plant succession, and use by mink. The pingos are described, and three types distinguished according to the plant com- munities they support, viz: grass, mixed vegetation type pingos have the greatest depth to permafrost, also other conditions suitable for mink natal dens.

Chromosome Number and Behavior in Arctic Mosses

1. To obtain independent data bearing on the hypothesis that the frequency of polyploidy increases with latitude, the chromosome number and meiotic behavior of mosses in arctic Alaska were investigated. Chromosome numbers were determined at meiosis in 55 species, representing 35 genera and 18 families, of which 44 species, 10 genera, and 1 family had not received previous cytological attention. 2. Precise temperature data taken 2 mm. and 2 cm. above the surface of a frost mound provide material for a more exact understanding of the microenvironment in which arctic mosses produce vegetative and reproductive structures. 3. The lowest chromosome number found was n = 6; the highest, n = 50. 4. Polyploidy occurs widely in arctic mosses but is no more frequent statistically than in comparable populations of mosses in California and Finland. No polyploid arctic races were found within species whose chromosome numbers have been reported in populations from more temperate regions. Several typically arctic species are highly polyploid and have chromosome numbers higher than those previously reported in their family; however, other typically arctic species showed no such increase. 5. Aneuploidy seems to be lacking in the arctic mosses investigated. 6. Minute bivalent chromosomes, whose component parts dissociate prematurely and may divide precociously, occurred in 22 of 55 species, which are presumably tetraploids or of higher ploidy. In view of the consistent behavior of these tiny chromosomes and their regular appearance in mosses, the terms "accessory chromosomes" or "isochromosomes" cannot properly be applied to them. 7. No higher degree of abnormal meiosis was observed in the arctic mosses than in more temperate regions, in spite of the more severe temperature regime. 8. The chromosome numbers of the various arctic families are compared, and the effect of proportional representation of different families on statistical comparisons is noted. 9. The different habitats of acrocarpous and pleurocarpous mosses result in a higher percentage of the former at higher latitudes, with concomitant effects on chromosome numbers and frequency of polyploidy. 10. It is concluded from this random sampling of chromosome numbers of arctic mosses that the frequency of polyploidy does not increase automatically with an increase in latitude, as postulated for higher plants.