The impact of surges on the ice-marginal landsystem of Tungnaárjökull, Iceland

Abstract

Geomorphological mapping of the Tungnaárjökull marginal zone based on the analysis of aerial and satellite photographs and field research were used as the basis for determining its morphogenesis. The differentiation of glacial and glaciofluvial forms, their association, and their mode of formation allowed five different domains of the Tungnaárjökull marginal zone to be distinguished. They record the distinct mechanism of glaciation and deglaciation of the glacier forefield, which is the result of the morphostructure of the volcanic substrate and the dynamics of the glacier snout. Structural and textural investigation of end moraine deposits and some proximal parts of the sandar allowed numerous glaciotectonic structures to be identified. Subglacial activity is conditioned by the local morphostructure of the substrate and transforms flat or undulated moraine surfaces and results in their drumlinisation. Reconstruction of the character of individual advances of Tungnaárjökull, from the end of the 19th century using geomorphological and sedimentological evidence within the ice marginal zone, suggest that they are consistent with surge-type advances. The configuration, dynamics and location of glacial streams in the marginal zone of Tungnaárjökull are conditioned by the Late Pleistocene volcanic relief. Where the arrangement of volcanic ridges is parallel to the glacier margin, its dynamics were restricted, creating groups of linear ice-contact forms. Where volcanic ridges were arranged perpendicularly to the glacier snout, conditions were suitable for the development of thrust end moraines and the formation of vast outwash plains.