Showing papers on "Permafrost published in 1975"

Microclimatic influences on ground temperatures and permafrost distribution mackenzie delta, northwest territories.

Abstract: Variations in ground thermal regime were studied over a small area in the east-central part of the Mackenzie Delta, Northwest Territories, about 50 km northwest of Inuvik. Vegetation shows a succes...

Late Precambrian glacial climate and the Earth's obliquity

Abstract: Late Precambrian (∼ 750±200 Ma) glaciogenic sequences exhibit substantial evidence for marked climatic inequability of seasonal and longer periodicity (10° to ∼ 106 yrs): (1) tillites are closely associated with dolomites, limestones and evaporites apparently of warm-water origin; (2) tillites occur with red beds and iron-formations whose iron probably was derived ultimately from lateritic weathering; (3) glacial dropstones occur locally within carbonates and iron-formations; (4) laminae, interpreted as varves by many workers, are common in argillites, carbonates and iron-formations; and (5) permafrost structures attributable to repeated seasonal changes of temperature are locally abundant. Such climatic, particularly seasonal inequability apparently conflicts however with the probable low (≲30°) palaeolatitudes of deposition of numerous late Precambrian glaciogenic sequences.The contradictions presented by such sequences may be resolved by postulating a considerably increased obliquity of the ecliptic (e) in late Precambrian time. Substantial increase in e would: (1) greatly amplify global seasonality; (2) weaken climatic zonation, thus allowing warm-water sedimentation and lateritic weathering over wide latitudes; and (3) increase the ratio of radiation received annually at either pole to that received at the equator, so when 54° < e < 126° low and middle latitudes (≤ 43°) would be glaciated in preference to the poles. Ice sheets and permafrost thus can be envisaged principally in low and middle latitudes with contiguous warm-water and iron-rich facies under a markedly seasonal climate. The concept of secular change of e is supported by other geological evidence.

The Classification and Geomorphic Implications of Thaw Lakes on the Arctic Coastal Plain, Alaska

Abstract: : The lakes of the Arctic Coastal Plain of northern Alaska were classified, based on size, shape, orientation and distribution, into six lake units and three nonlake units. Regional slope and relief were demonstrated to control lake size, the largest lakes occurring on the flattest, northernmost segment of the Coastal Plain. Using ERTS-1 sequential imagery and existing photography and data, lakes were grouped according to three depth ranges, 1 m, 1-2 m and 2 m. Deepest lakes have the longest period of summer ice cover. Ice on shallow lakes melts the earliest. Maximum depths of lakes were computed based on ice volume content of the perennially frozen ground (permafrost) and these agreed with observed values and ranges. The lake classification and regional ERTS-1 coverage also appear to provide additional information on the limits of late-Pleistocene transgressions on the Coastal Plain.

Ground and airborne resistivity surveys of permafrost near fairbanks, alaska

Abstract: In permafrost regions investigations for such geotechnical endeavors as route selection for roads and pipelines and site investigations for buildings and dam construction often require that a careful assessment be made of the presence or absence of frozen ground, of the ice content of frozen ground, and of the depth of frozen ground. In the vicinity of Fairbanks, Alaska, where the permafrost is discontinuous, ground and airborne methods of mapping electrical resistivity using radiowaves were tested as means of delineating permafrost. When the resistivity maps are compared with surficial geological data, the following conclusions are reached: (1) In areas of fine‐grained sediments, where the near surface sediments are relatively uniform, VLF resistivity delineates permafrost. (2) In areas where surface sediments vary widely (flood plains), VLF resistivity shows little information on permafrost conditions but can provide other important geotechnical information, such as, depth to bedrock, surface soil type,...

Tree ring record of soil movements on permafrost

Abstract: Trees growing on severely cryoturbed soils on of high activity and quiescence in the last 160 permafrost terrain produce reaction wood in years. Such periods can be matched in two areas response to tilting of trees by ground heave 450 km apart, but occur two years earlier in the movements. A total of 157 tree disks taken from north than in the south. Above-average levels 59 different earth hummocks show multiple tilt- of activity are indicated for the period 1847 to ing and recovery. The direction of tilt is general- 1943, and low levels of activity during the last ly away from the center of active hummocks. two decades. There are indications that high The chronology of ground heave movements as levels of activity are related to higher than norrecorded by reaction wood shows brief periods mal fall temperatures and precipitation.

Thermal Conductivity of Some Ice-rich Permafrost Soils

Abstract: Values are presented for the thermal conductivity of frozen and thawed ice rich permafrost soils from Inuvik, Northwest Territories, measured under field and laboratory conditions with a cylindrica...

Depositional Environments and Sediment Characteristics of the Colville and Adjacent Deltas, Northern Arctic Alaska

Abstract: Polar deltas, typified by those on Alaska's North Slope, which have their drainage basins totally in the permafrost region and discharge into a polar sea, are significantly different from lower latitude deltas. In the arctic, features classically related to delta-front platform and slope facies are not well defined and certain continental facies are either nonexistent or less well developed. Except during occasional storms the North Slope deltas are exposed to low energy hydraulic conditions. Mean size is the only textural parameter that can be used to differentiate sediments of the estuary, lagoon, coastal beach, bay and open marine environments. Except for coastal plain and beach deposits, the deltaic sediments are poorly to very poorly sorted silty sands or sand-silt-clays that have nearly symmetrical to positive-skewed size distributions. The coastal plain is comprised of tundra with associated permafrost, as well as gravels derived from underlying Quaternary material. The coastal beach foreshore consists of moderately to poorly sorted sands or gravelly sands that have nearly symmetrical to positive-skewed size distributions. The transport of gravels by ice-rafting is insignificant. Forty-three percent of the fluvial discharge occurs during three weeks in the spring and is in the form of an overflow on sea ice. Lack of discrete heavy mineral laminae reflect a lack of intense hydraulic sorting. Terrigenous input primarily determines the clay mineral assemblage at any locality in the river. However, differences between fluvial and marine deltaic environments are discernible. Broad facies variations within the nearshore materials suggest that clay mineral suites may be of use in explaining sediment transport directions. Differences in the chemistry of arctic and lower latitude deltaic sediments are recognizable as well as are variations among the subfacies of the arctic deltas.

Soils of the Subarctic in the Lower Mackenzie Basin

Abstract: Nearly all of the medium- and fine-textured surficial materials are permanently frozen within one metre of the surface and have a hummocky micro-relief. Indications of physical disturbance due to cryogenic processes are ubiquitous, and organic matter distributions ranges from incorporated, relatively undecomposed material to mobile organic acids. On the other hand, well-drained coarse-textured materials have no permafrost and are characterized by Brunisolic soil development. Profile descriptions and characterizing analyses are discussed with respect to cryogenic soil-forming processes and soil classification. The suggestion is made that there is a need for re-evaluation of traditional concepts of soil development when dealing with permafrost soils of the Subarctic.

Structure of Subarctic Forests on Hummocky Permafrost Terrain in Northwestern Canada

Abstract: Examination of 30 stands in subarctic woodlands showed that most were even-aged, having been established after fires Most fires killed all trees in the stand, but in some instances some trees surv

Some Aspects of a Simple Secondary Creep Model for Deformations in Permafrost Slopes

Abstract: This study presents the solution to a simple model for deformations due to secondary creep in permafrost slopes. By introducing a constitutive relationship, or flow law, for ice into the model it i...

Influence of white spruce trees on permafrost-table microtopography, Mackenzie River Delta

Abstract: The topography of the permafrost table in the Mackenzie River Delta is remarkably uniform. However, differences in active layer thickness are characteristically found around the stems of white spruce trees where conical depressions occur in the permafrost table. The locally increased active layer thickness appears to result from the interaction of the following factors, all of which cause greater heat diffusivity into the soil near tree stems: (1) some 25% of the gross rainfall is intercepted by individual spruce crowns, which causes a corresponding decrease in soil moisture below the tree; (2) accelerated sediment deposition around spruce stems during the spring flood creates small alluvial deposits that provide a locally better drained site; (3) the growth of insulative mosses around tree stems is also retarded by the increased sediment deposition; and (4) the low-albedo slopes of alluvial deposits surrounding tree stems intercept more solar radiation than the normal flat surfaces away from trees.

Mechanical Properties of Simulated Deep Permafrost

Abstract: Exxon Production Research Co. evaluated the viscoelastic and yield properties of simulated deep permafrost from creep tests on frozen and unfrozen 20-40 mesh sand. Overburden pressure associated with deep permafrost was imposed on the samples by freezing under constant confining pressure and maintaining this pressure during the tests. The results showed that both thawed and frozen simulated permafrost behaved as a delayed elastic material before yield and as a coulomb plastic material after yield. The appropriate viscoelastic material constants were determined by correlating the test data with a mathematical model for the delayed elastic material. The results, together with Prudhoe Bay field test data, indicate that the creep response of deep permafrost, subject to loading and refreezing, is negligible in comparison to the elastic and yield response.

Permafrost am Pico de Orizaba/Mexiko

Abstract: . In Mexico (ca. 19° N) permafrost is found on Pico de Orizaba volcano between 5000 and 4600 m altitude. The permafrost is fossil. Different types of ground ice can be distinguished. The permafrost occurrence beneath the snowline (ca. 5000 m) shows that in Mexico snowline and lower altitudinal limit of permafrost do not agree with the pattern as it is given by Baranov for the tropical zone.

Intermittent arctic streams and their influence on landforms

Abstract: Summary Concentration of stream flow in a short period of time is one of the similarities shared by the arid zone and the zone of continuous permafrost. However, in the Arctic the seasonality of flooding is likely to be more regular than in the arid zone because water is stored in the form of snow for a long period of time and its release is dependent upon the seasonal character of temperature changes. Much of the area in continuous permafrost experiences a repetition of short periods of heavy flooding separated by long periods of extremely low water. Thus, floodplains, especially along braided streams, are exposed to wind action during most of the snow free period. Thermal erosion and seasonally concentrated runoff are often responsible for rapid bank retreat along many channels and for the construction of a variety of depositional forms many of which are highly ephemeral. Although floodwater is the main agent in erosion, transportation and deposition in the Arctic it is not the only one. Ice, which moves downstream during breakup exerts an influence on many forms and is responsible for the presence of nonsorted, randomly located deposits in floodplains. Much morphologic change in the zone of continuous permafrost, like that in the arid zone, tends to be concentrated in a short period of time. However, such extreme concentration of morphologic activity is not surprising for it is also typical of other physical and biologic activity.

Reticulate Ice Veins in Permafrost, Northern Canada: Discussion

Abstract: 'Paper by Mackay, J . R. Can. Geotech. J . 11(2), p p 230-237. In these soils horizontal ice lenses are rarely observed by themselves except as sub-horizontal lenses in the active layer. The discussers would like to expand upon one theory noted by the author, by suggesting two mechanisms for reticulate ice vein growth that cause cracking in the unfrozen soil ahead of the advancing freezing front. Water is drawn into, or forced into, these cracks where, in time, it is frozen by the 0 O C isotherm. It is to be noted that while the writers agree with Maskay

Permafrost profiles in the continental divide region of alberta and british columbia

Abstract: Two permafrost profiles in the alpine region permafrost is only the second from the Rocky of Banff National Park, Alberta, and an ad- Mountain region of Alberta and southern jacent region of British Columbia were observed British Columbia. throughout the summer of 1970. This report of

Landscape Mapping in the Mackenzie River Valley

Abstract: Terrain over a wide area of the Mackenzie River valley was evaluated on the basis of vegetation-landform patterns, identifiable in air photographs as landscape units, which could be grouped into regions with climatic connotations. From a ground inspection of selected sites, it was shown that each landscape unit comprised a complex of elements characterized by permafrost relationships. An evaluation of the terrain over a much wider area was extrapolated from the air photographs. Vegetation or landform alone did not permit of a satisfactory delineation of regions with climatic connotations, since they were both so diffusely distributed.