Anders Rapp

Alpine Debris Flows in Northern Scandinavia: Morphology and dating by lichenometry

ABSTRACTThe effects of an extreme rainfall triggering debris flows (mudflows) in the mountains S of Abisko, N Sweden, in 1979, are evaluated with regard to geomorphological impact. Several older events of debris flows in the same area during postglacial time are evident in the morphology of the slopes. Where such flows have occurred repeatedly, debris accumulations superficially similar to alluvial cones and referred to as debris flow cones are built. An attempt at dating old flows by means of lichenometry indicated at least four earlier events within the last 2700 years in Nissunvagge. A map of the spatial pattern of known rainfall-triggered mass movements in northern Lappland is presented to support the hypothesis of geomorphic impact of extreme rainfall in three area size classes called regions, cells and spots.

Slope Erosion Due to Extreme Rainfall in the Scandinavian Mountains

AbstractHeavy rainstorms in summer and autumn trigger landslides and debris flow in arctic mountains. However, the recurrence intervals are long. Some cases from Scandinavia are described. They wer...

Mass movements, nivation processes and climatic fluctuations in northern Scandinavian mountains

Climatic fluctuations during the twentieth century in northern Scandinavia and Spitsbergen may have influenced the frequency of rainfall-triggered mass movements such as debris flows, with a shorter recurrence interval during colder periods before c. 1920 and after c. 1960, and less frequent occurrence during the intervening warm period. However, precipitation data are contradictory regarding contrasts between warm and cold periods, and the recorded high number of debris flow events during later decades may also be a result of improved observations. Studies of nivation processes and snow cover distribution may provide additional information on climatic fluctuations. Examples are given of the use of nivation landforms as climatic indicators.

Nivation Hollows and Glacial Cirques in Söderåsen, Scania, South Sweden

ABSTRACTThe author leads a research project to test his theory of nival erosion and glacial protection of cirque forms in Scania (Rapp 1982 a and b), with comparative studies in Lappland and in middle and south Europe. The project will test the following postulates.The tundra periods in Scania, e.g. the Older and Younger Dryas had permafrost climate with strong effects of snow drifting by easterly and westerly winter storms. This is likely from observations of fossil ice-wedge casts on sandy plains in Scania, and from wind-polished bedrock and blocks with fluting marks, from easterly and westerly directions (G. Johnsson, A. Mattson, H. Svensson). Large masses of snow were then trapped in the valleys of Soderasen, forming nivation hollows and glacial cirques. This was also the case during the much longer tundra periods before the advances of the Quaternary main ice sheets over Scania. Small local glaciers and many nivation hollows were formed and grew, before the major ice advances. The canyons, cirques an...

NIVATION AND LOCAL GLACIATION IN N. AND S. SWEDEN. A PROGRESS REPORT

An ongoing geomorphological research project on nivation and local glaciation is testing the following working ./ hypothesis. After the main Weichselian deglaciation in south Sweden, periods of cold tundra conditions returned, e.g. in the Younger Dryas period. Fossil ice-wedge casts and rocks with wind-polis- ^// hed facets and flute marks indicate permafrost climate and _ strong winds with snow-drifting from easterly and westerly direc- tions. Large masses of drifting snow were trapped in the canyon valleys of Soderasen and other horst ridges, where nivation / hollows and small glacial cirques were slightly rejuvenated. Ni- / veo-eolian sand was deposited in some hollows and also incorpo- // rated in some moraine-like deposits. The bedrock hollows and cirques were mainly excavated during the much longer tundra 64// periods before the advances of the Quaternary main ice sheets over Scania. But the hollows survived the erosional impact of the ice sheets. The work to test the hypothesis is making progress, by analysis/// of the Late-Glacial forms and material in south Sweden, by \ comparisons with landforms, material and processes in the actual , // mountain tundra of Abisko in the north, and by comparisons - /

Case studies of geoprocesses and environmental change in mountains of northern Sweden

This paper on selected case studies makes comparisons with climate parameters, slope erosion caused by rapid snow melt and slushflows (slush avalanches, slushers), and slope erosion due to debris flows or slides, triggered by heavy rainfalls. The slushers and debris flows are viewed in a 100-year time perspective and compared with observations at other sites and with records from railway and

Landslides in the Mgeta Area, Western Uluguru Mountains, Tanzania: Geomorphological effects of sudden heavy rainfall

Landsliding triggered by intense rainstorms is a major erosional process affecting steep, soil-covered slopes in a variety of climatic zones. This paper is a case study of the geomorphological and ...

Large Nonsorted Polygons in Padjelanta National Park, Swedish Lappland

Large no nsorted polygons in tundra areas underlain by discontinuous permafrost occur in Padjelanta National Park, northern Sweden (67° 16′ N; 16°52′ E). Excavations in those of the polygons develo...