Maskevarri Ráhppát in Finnmark, northern Norway – is it an earthquake-induced landform complex?
- Geological Survey of Finland, P. O. Box 77, 96101 Rovaniemi, Finland
Abstract. The Sami word ráhppát means rough bouldery/stony terrain with sharp-relief topography in Finnmark, northern Norway. Ráhppát is a common name in the region of the Younger Dryas landforms, yet the origin of ráhppát has remained obscure. The timing of the Younger Dryas is concomitant with the maximum neotectonic fault instability in Fennoscandia. Hence, earthquake activity may have been one of the contributing factors for the Younger Dryas morphologies. Ráhppát on the Maskevarri fell, classified as a part of Tromsø-Lyngen sub-stage of the Younger Dryas, was studied by means of geomorphology and measurements of electrical-sedimentary anisotropy. Ráhppát was found to be built up of an anastomosing network of stony esker-like ridges and mounds bordered with arch-shaped and sinusoidal ridges. These bordering ridges exhibit sedimentary (azimuthal soil electrical conductivity) anisotropy parallel-to-ridge trends and were interconnected to meltwater gullies suggesting generation through short-lived conduit infills. We did not find electrical-sedimentary evidence to support the concept of englacial thrusting and/or compression, often described for Younger Dryas moraines. Maskevarri Ráhppát is typified by ~ 500 ponds and small lakes on three different elevations descending in an up-ice direction. These may have generated through late glacial earthquake(s) also contributing to subglacial deformation of Maskevarri Ráhppát.