Search

Simultaneously with geological field investigations at the surge-type glacier Brúarjökull in August 2003, aerial photographs covering the central part of the glacier including the Kringilsárrani area were recorded with the purpose of mapping glacial landforms. A glacial geomorphological map has been completed at a scale 1:16,000 including more than 20,000 landforms from an area of c. 8 km². Manual classification of landforms was carried out directly in stereoscopic view using a digital photogrammetric workstation taking full advantage of the texture, topography and spatial context of individual landforms. We mapped subglacial lineations such as flutes and drumlins on till plains, pitted outwash, eskers, minor meandering ridges, crevasse fill ridges, ice-free dead-ice moraine and concertina ridges, outwash fans and lake sediment plains. In addition, erosional drainage channels, ice-marginal ridges, overridden end-moraines, and extra-marginal ice wedge polygons and collapsed palsas were mapped. The mapped glacial landforms originate from at least four surges: pre-1810, 1810, 1890 and 1964. The distribution of landforms on the Brúarjökull forefield has close resemblance to landform assemblages of palaeo-ice streams. The present terrain surface at Brúarjökull is the cumulated result of multiple landform generations because each surge has superimposed a new association of landforms on older surfaces. [ABSTRACT FROM AUTHOR]

In the 1980s, the NE part of the principal outlet glacier Kötlujökull on the east flank of the temperate ice cap Mýrdalsjökull was advancing; the maximum average rate of annual advance of 32 m was recorded during the period 1982–84. Along the advancing glacier margin a frontal push moraine was currently being produced by continuous mixing of proglacially thrust and folded outwash sediments with material avalanched down the steep front of the debris-covered glacier snout. During periods of fast glacier advance, the pushed ridge was mainly a combination of slabs of outwash deposits, but during periods of slow glacier advance, the pushed ridge chiefly consisted of front cliff-fall debris. By the end of the 1980s the glacier advance had stopped, and during the 1990s the most terminal part of the debris-mantled glacier developed into a 300–500 m wide zone of dead ice with a complex morphology of steep-sided mounds, ridges, collapsing edges and ice walls. At present the total lowering of the ice-cored terrain amounts to 25–30 m. The glacier has left a single-crested ridge, 4–7 m high, without evidence of thrusting; the ridge consists exclusively of front cliff-fall debris and can be defined as a dump moraine. Without having observed the active mechanism of ridge formation throughout the 1980s, we could mistakenly have interpreted this ridge as a moraine ridge associated with a pause in a general ice recession. However, the dump-moraine ridge marks the maximum extent of a sustained glacier advance, and during this advance the basic mechanisms involved in the frontal moraine formation were pushing and thrusting. [ABSTRACT FROM AUTHOR]