Glacier Ice and Its Domain

Abstract

Glacier ice forms from accumulated old snow, and the erosive power of glaciers flowing down-valley as well as the related production and deposition of large amounts of rock debris are responsible for the large inventory of glacial landforms. Even though we are living in a warm climatic period at the moment (the Holocene interglacial period), glaciers are still common in the cold climates of the higher latitudes as well as in high mountains all over the Earth. There are different types of glaciers depending on the general ice budget, ice temperatures or the general topographical circumstances. Glacier ice may entirely cover large areas as in the case of inland ice and plateau glaciers, or it can be restricted to the mountain relief such as glaciers in cirques, or valley glaciers. Glaciers that exit mountain belts and advance into the foreland are called piedmont glaciers. Glaciers exert enormous erosive forces due to their weight and their ability to transport and use rock debris of different sizes that are frozen at the glacier’s base. Rock debris scratches the hard rock at the valley floor and creates typical striae or striations as well as polishing of rock surfaces where finer particles are incorporated in the basal ice. Probably the most prominent example for the smooth forms of glacial erosion and polishing in hard rock surfaces are “roches moutonnées”, which are characterised by a whaleback-like shape and an asymmetrical long profile. Other well-known forms are cirques particularly in higher mountain areas and U-shaped cross profiles of valleys which have been eroded by former glaciers. In turn, moraine ridges consisting of glacial debris give depositional evidence of former glaciations and deglaciations. Large amounts of debris material are transported on the surface, within the glacier, at its bottom, or along its lateral boundaries as “moraines”. The sediments of these moraines are called till. After deglaciation, remnants of the lateral deposits remain in the form of long and sharp-crested ridges (lateral moraines) and large amounts of debris that were pushed in front of the former glacier are left to form a terminal moraine. Other forms are created below the moving ice such as “drumlins”, or as relics of subglacial meltwater streams below the glacier such as the long and narrow “eskers” or “osers”.