Submarine medial moraines in Hambergbukta, southeastern Spitsbergen
Sediments are incorporated into glaciers mainly by basal erosion and freeze-on, and by debris-fall onto the ice surface along the slopes of adjacent mountainsides. Flow-parallel debris ridges formed at the confluence of glaciers are known as medial moraines (Benn & Evans 2010). Medial moraines have a number of different origins (Eyles & Rogerson 1978; Benn & Evans 2010), including ingestion of basal marginal debris in deep crevasses and redistribution of supra-, en- and subglacial debris in the shear zone between converging glaciers (e.g. Sharp 1988; Vere & Benn 1989; Hambrey & Glasser 2003). Medial moraines up to tens of kilometres long and tens of metres high can be preserved after glacier retreat, marking the former flow path of ice masses. Medial moraines have also been shown to exert significant control over surging glaciers by inhibiting and/or redirecting glacier flow. Locally persistent subglacial meltwater conduits located under the medial moraines can also inhibit glacier surges by draining subglacial meltwater efficiently and decreasing basal water pressure (Benn et al. 2009).

Hambergbukta …