A Framework for the Investigation of Medial Moraine Formation: Austerdalsbreen, Norway, and Berendon Glacier, British Columbia, Canada

Abstract

Morphology of medial moraines on Austerdalsbreen, Norway, and Berendon Glacier, British Columbia, depends upon englacial debris supply. Major sub-types of this "ablation-dominant" model are related to the zone of debris entrainment relative to the firn line, and the manner of entrainment.On Austerdalsbreen, debris derived from extraglacial bedrock slopes is entrained via crevasses at the confluence of two ice-cap outlet glaciers below the firn line. Revelation of crevasse-bound debris generates a distinct ice-cored morphology which is destroyed as crevasse bottoms are revealed down-glacier.On Berendon Glacier ice streams coalesce above and below the firn line. Above the firn line, debris from extraglacial rock outcrops, subnival and subglacial zones, undergoes seasonal sedimentation with snowfall, and extends throughout the ice depth. Distinct moraine morphology in the terminal zone is related to continuing debris supply. Most debris is transported at depth near the glacier base.An "ice-stream interaction" model where medial moraines formed below the firn line from the confluence of ice streams with large lateral moraine load are morphologically controlled by flow, explains morphology on the Berendon Glacier in the main confluence zone only. Down-glacier, this moraine becomes "ablation dominant". A minor "avalanche-type" model is also recognized.

Formation and reorientation of structure in the surge‐type glacier Kongsvegen, Svalbard

“…Gripp (1929) first proposed crevasse-filling as a mechanism for incorporating sediment into ice during stagnation and settling of ice on to its substratum. Similar mechanisms were proposed by: Eyles and Rogerson (1978) to explain sediments injected into deep marginal crevasses, followed by redistribution by surging; Sharp (1985b) to explain till ridges in the forefield of the surge-type glacier Eyjabakkajökull, Iceland; by van der Meer (1992) and Boulton et al (1996) to explain the crevasse-intrusion ridges formed on the island of Coraholmen during the surge of Sefstrombreen, Svalbard; and Evans and Rea (1999) to explain sediment Voight (1966). (c) Structures mapped from 1969 aerial photographs.…”

Structural glaciology of a temperate maritime glacier: lower fox glacier, new zealand

“…The material is then 'exhumed' by the rapid surface melt, causing the debris to accumulate on the surface. On this basis, the medial moraine corresponds to the AD2 model of Eyles and Rogerson (1978), and the lack of significant positive relief prior to this point of emergence is a reflection of the low debris concentrations, and the discontinuous debris-supply.…”

“…A comprehensive medial moraine classification scheme was proposed by Eyles and Rogerson (1978) and has been described in detail by Benn and Evans (1998), based on the relationship between sediment supply and morphological development. Three models of medial moraine formation have been postulated (e.g.…”

Landslide‐glacier interaction in a neoparaglacial setting at tverrbytnede, jotunheimen, southern norway

“…Its coarse clast size and angular boulders are not inconsistent with this hypothesis as much of the debris in medial moraines originates from headwall rockfalls and is transported passively along supraglacial or high-level englacial pathways (Boulton 1978;Eyles and Rogerson 1978). The subangular to subrounded component (Fig.…”