Murtoot--mitä ne ovat

The present paper focuses on murtoo landforms reporting results and understanding gained so far in the RewarD project funded by the Academy of Finland (https://sites.utu.fi/reward/etusivu/reward-project). Based on evidence from remote sensing and numerous murtoo excavations in Finland and Sweden, we describe three main observations. First, murtoos are formed subglacially, which is seen from their orientation parallel to ice flow and associations with with eskers and subglacial meltwater routes. For example, murtoos are sometimes overlain by eskers, glacial lineations and De Geer moraine ridges. Murtoos are also covered by loose diamicton (flow till) that was deposited in the final phase of deglaciation. Second, the morphometric diversity of murtoos and murtoo-related landforms in the Fennoscandian Ice Sheet area is significant, with triangle-type murtoos being only the most representative and distinctive examples of murtoo landforms. Third, murtoos are depositional landforms composed of silt/clay-poor, sandy and gravelly diamictons interbedded with sorted glaciofluvial sediments. Accordingly, we suggest murtoo sediments are produced by pulsed, highly sediment concentrated flows during deglaciation with only weak glaciotectonic deformation. Importantly, murtoos potentially represent a transition form from non-channelized to channelized subglacial drainage networks, which is important from the viewpoint of glacial hydrology and ice-sheet dynamics. Murtoos may thus provide new information for glacial modelling approaches by introducing the missing link between inefficient and efficient subglacial drainage, and thereby also increase our understanding on how current glaciers will behave in the warming climate.