Maskevarri Ráhppát in Finnmark, North Norway – is it an earthquake induced landform complex?

Abstract

Abstract. The Sami word ráhppát means rough bouldery/stony terrain with sharp-relief topography in Finnmark, North Norway. Ráhppáts are common features in the region of the Younger Dryas landforms, yet their origin has remained obscure. The timing of the Younger Dryas is concomitant with the maximum neotectonic fault instability in Fennoscandia, hence earthquake activity was 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 a network of stony ridges and mounds on fell terraces 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 terrace elevations descending in an up-ice direction. These escarpments may have generated trough late glacial earthquake(s) contributing to subglacial deformation of Maskevarri Ráhppát.