Changing mountain permafrost from the 1970s to today – comparing two examples from NiwotRidge, Colorado Front Range, USA
Années 1970-2009 ; Changement climatique ; Colorado ; Etats-Unis ; Exposition de versant ; Gélifluxion ; Modèle ; Montagne ; NiwotRidge ; Pergélisol ; Périglaciaire ; Rocky Mountains ; Température du sol ; Tomographie de résistivité électrique
The study site NiwotRidge, situated at ~3600 m a.s.l. in the Front Range of the Rocky Mountains, Colorado, USA, offers permafrost distribution data from the early 1970s. The AA. used 4 different approaches (air photographs and survey stakes
at 3600 m during 1970, if so, permafrost degradation on south facing slopes on NiwotRidge was not driven by recent climate change. However, north-facing slopes do cover permafrost, and certainly did in the 1970s, they are most probably affected by climate
This study measures energy and moisture exchanges in the alpine fellfield on NiwotRidge, in order to, first, assess the influence of topoclimate on energy budget components during a period of summer drought, and second, explain the distribution
Analyse d'observations faites pendant 58 jours, automne 1972, NiwotRidge, Colorado Front Range. Températures enregistrées sur la roche en place. Analyse statistique des phases de gel et de dégel.
This study evaluates 2 models (frost heave and deflation) for the formation of nonsorted stony earth circles in 2 populations of circles on NiwotRidge, Colorado, by examination of the coarse particle and silt distributions within the circles using
To isolate the influence of sampling-surface orientation on the macrofabric of periglacial colluvial deposits, clast orientation measurements were obtained from 7 paired horizontal and vertical exposures in turf-banked solifluction lobes on Niwot
Ridge, Colorado Front Range. Fabrics obtained from vertical faces were stronger than those from horizontal exposures in 6 of the pairs. Near-horizontal sampling surfaces yield less biased results than vertical exposures, owing to operator perceptions
Distribution, morphology and structure of sea ice pressure ridges in the Baltic Sea
This is a pioneer work to carry out a detailed study of sea ice pressure ridges in the Baltic Sea. The results are based on field measurements. They include measurements of such as the inside structure of ridges and the orientation of ice blocks
in the ridges sails. The aim of this paper is to serve as a basic information about the structure, morphology and distribution of the pressure ridges in the Baltic Sea. The results are compared with the information about the ridges in the Arctic Seas.
The objectives for this article are to describe the ridge-and-runnel enigma that exists in coastal geomorphology and to explain evidence for episodic ridge-and-runnel occurrence from a California case study. Three hypotheses are discussed : 1) quasi
-stationary ridges and runnels may reflect swash-bar growth by constructive short-period waves, especially on macrotidal coasts| 2) mobile ridges and runnels may be muted expressions of longshore bars and throughs migrating onshore| 3) ridges and runnels may
Formal analysis of ridge and channel patterns in maturely eroded terrain
This paper focuses on the formal description rather than the physical explanation of the ridge and channel patterns in maturely dissected terrain| the object of the description is the connectivity within and between these patterns rather than
their geometry. The A. investigates the topological relations between ridge and channel networks, with particular emphasis on the interdependencies between ridge and channel links and paths, and the drainage areas delineated by them.
The response of the Pacific plate to oceanic island and seamount loads has been used to estimate the distribution of ridge crest and off-ridge volcanism on the plate since the late Jurassic. The most extensive event, forming the Hess rise, Line
Islands ridge, Necker ridge, and Robbie ridge, occurred on the Pacific/Farallon and Pacific/Phoenix ridge crests during the interval 90-120Myr BP (Barremian to Turonian). This event, which extended over a much larger area than comparable volcanism
Fabric, paleomagnetism, and interpretation of pre-Illinoian diamictons and paleosols on Cloudy Ridge and Milk River Ridge, Alberta and Montana
L'orientation des cailloux et leurs caractéristiques sédimentologiques indiquent que les diamictons du pré-Wisconsinien (Drift de Kennedy) provenant du Cloudy Ridge (Alberta) et du Milk River Ridge (Montana) sont d'origine glaciaire plutôt que
colluviale. Les données paléomagnétiques et les comparaisons faites avec des séquences de paléosols et de tills similaires permettent de dater les tills du Cloudy Ridge et du Milk River Ridge.
The shoreface-connected ridges along the central Dutch coast
The present study adresses to the questions how the shoreface-connected ridges along the central part of the Dutch coast were formed and what their behaviour is under the present hydrodynamic conditions. The study is based on field observations
and model computations. The field observations focus on the present hydrodynamic and sediment transport processes, on the resulting morphological and sedimentological response, and on the geologic evolution of the ridges. - (AGD)
Probable paleoperiglacial morphosequences in the northern Blue Ridge
Bloc ; Dépôt de pente ; Etats-Unis ; Géographie de l'Amérique ; Lichénométrie ; Maryland ; Northern Blue Ridge ; Pennsylvania ; Périglaciaire
This paper focuses on deposits and structures with a probable paleoperiglacial origin and their relevance to landscape evolution of the Northern Blue Ridge, Maryland and Pennsylvania. The paper's purpose is threefold : to describe the periglacial
Genesis of an elongated ridge at Jæren, southwest Norway : drumlin or marginal moraine?
This paper presents results of morphological, sedimentological and glaciotectonic analyses of one of these ridges at Obrestad. It is suggested that the ridge has been formed by drumlinization of outwash deposits by a glacier advancing towards
Comparison of morphographic features and internal structures of the coastal ridges off the Belgian coast with similar ridge systems in International Colloquy on the Quaternary and Tertiary geology of the Southern Bight, North Sea. Collected