The Formation of Medial Moraines on Alpine Glaciers

1983

J. Glaciol.

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The relationship between supraglacial lateral moraines and lateral dump moraines at Arolla. Switzerland, is discussed. A detailed study of the lateral moraines of glacier de Tsidjiore Nouve reveals their complex form (as superimposed and nested ridges) and the current mode of development (possibly related to the passage of a kinematic wave). Sedimentological analysis indicates that much of the constituent debris is of supraglacial origin; it is transported either directly from the base of slopes flanking the Pigne d’Arolla ice-fall or via englacial septa comprising marginal sediment incorporated in the accumulation zone. A calculation of the volume of debris in the lateral moraines suggests that glacier de Tsidjiore Nouve has recently been more active in transporting and depositing supraglacial debris than in glacial erosion sensu stricto.

“…(i) Supraglacia/ lateral moraines occur on all the glaciers, and are in many respects comparable with medial moraines in the area (Small and others, 1979). However.…”

Section: Introductionmentioning

confidence: 93%

Lateral Moraines of Glacier De Tsidjiore Nouve: Form, Development, and Implications

1983

J. Glaciol.

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“…The detailed morphology of the two main medial moraines of the Haut Glacier d'Arolla (the western extending the length of the glacier from the base of La Vierge, and the eastern "emerging" from the ice surface at about 1 km from the snout) has been described and discussed by Small and others (1979). During the 1983 ablation season, unusually favourable snow conditions permitted a close examination of the nature and sources of the sediment in these moraines, which revealed important new information.…”

Section: Field Settingmentioning

confidence: 99%

Medial Moraines of the Haut Glacier D’arolla, Valais, Switzerland: Debris Supply and Implications For Moraine Formation

Gómez

1985

J. Glaciol.

ABSTRACT. The Haut Glacier d' Arolla displays three medial moraines: an ablation-dominant moraine east of the glacier centre line, an ice-stream interaction moraine west of the glacier centre line, and a medial-lateral supraglacial moraine complex along the western margin of the glacier. The eastern moraine is formed by the emergence of coarse angular clasts from a series of short longitudinal debris bands 1 km from the glacier terminus; this debris is derived from rock falls at the glacier head-wall, and follows a low-level transport path through the glacier. The western moraine is formed partly by the direct fall of weathered debris on to the ice surface at a point 2.6 km from the snout, but it receives further increments of sediment from extensive longitudinal en glacial debris bands developed from the convergence of two ice streams with lateral englacial debris septa. The medial-lateral moraine complex is formed largely by rock falls from the western valley wall, but is also nourished by a debris layer developed at the base of the small tributary Glacier de la Mitre. This layer crops out at the eastern margin of the re-sultant inset ice stream, and releases more rounded, abraded and comminuted rock fragments to supplement the surface debris cover of supraglacial origin. RESUME.

“…They fall clearly into the category of “beaded” moraines identified by Embleton and King (1968). The forms of such moraines pose problems of intrinsic interest (Small and others 1979); in the present context, however, the origin of the englacial debris is considered, primarily for the light it sheds on erosive and transportational mechanisms of valley glaciers with large ice falls.…”

Section: Introductionmentioning

confidence: 99%

The Nature and Origin of Debris Layers within Glacier De Tsidjiore Nouve, Valais, Switzerland

Gómez

1981

Ann. Glaciol.

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The development of medial moraines on the Glacier de Tsidjiore Nouve is related to numerous englacial debris layers of limited dimensions, which are exposed at the glacier surface below the Pigne d’Arolla ice fall. Previous research has suggested that such layers result either from high-level transport of debris, derived from rock weathering and/or glacial erosion in the accumulation zone, or from shearing up of subglacial debris owing to intense compressive stresses in the glacier. The morphology of the debris layers is investigated in the field, and samples are subjected to particle-size analysis. It is concluded that constituent debris is derived largely from exposed faces of rock between the upper and lower firn basins, but that a subglacial component is present. Entry of the debris into the glacier is possibly by way of crevasses on the lower firn basin.