Breiðamerkurjökull is the second largest outletglacier of the southern margin of Vatnajökull with well-developed medial moraines. The nunataks of Esjufjöll and Mavabyggdir feed debris onto the glacier to produce the ice stream interaction medial moraines. The maritime, cold-temperate climate of the region is probably responsible for the late winter readvances of the receding glacier margins in southeast Iceland, thereby giving rise to the deposition of numerous, often annual, recessional push moraines.
The oldest deposits in the Breiðjamerkurjökull foreland are those exposed around the Jökulsárlón depression. During the settlement period of Iceland from AD 874 to AD 930 the outlet glaciers of southern Vatnajökull are thought to have been 20km behind their present margins.
The most extensive and sharply defined moraines on the glacier forelands are the small push moraines. These moraines are usually no more than 5m high but can be traced continuously over distances in excess of 3 km. Greater relief occurs locally where ice-marginal stability has resulted in the stacking of push moraines. Push moraines have been produced annually since 1965 on the west lobe foreland. The plan-form of these push moraines reveals crenulated, lobate or saw-tooth crests whose rerentrants coincide with longitudinal crevasses at the glacier margin (Evans et al., 2002).
Push moraines (Evans et al., 2002)
As the two glaciers Breiðamerkurjökull and Fjallsjökull have receeded from their Little Ice Age maximum positions they have uncovered large depressions in which the lakes Fjallsárlón, Breiðarlón, Jökulsárlón and Stemmulón have evolved. Because the occupancy of the depressions by lakes has been generally short lived, glacilacustrine sediments and shorelines are not widespread although some extensive shoreline fragments document the evolution of Jökulsárlón. Most significantly with respect to the lakes, discharges within the lake spillways have constructed large, terraced outwash fans. The most impressive of these occurs in the corridor between Breiðarlón and Fjallarlón where the diversion of the meltwater drainage from west Breðamerkurjökull after 1960 led to the long term progradation and incision of glacifluvial sediments around moraine and till covered topographic high points (Evans et al., 2002).
The following maps show clearly the change of the proglacial lakes and that proglacial outwash streams drained either away from the glacier margin to produce sandur fans or parallel to the margin due to topographic constraints on the foreland to produce ice marginparallel outwash tracts and kame terraces. Sandur fans typically emanate from subglacial or englacial meltwater portals during periods of relative ice marginal stability, resulting in the development of pitted ice-proximal fan surfaces and steep ice-contact faces. Additionally, eskers are often linked directly to the fan apices (Evans et al., 2002).