Glacier–rock glacier interactions in the eastern Hindu Kush, Nuristan, Afghanistan [35.92,71.13] in the period 1976–2019

Abstract

Landsystem relationships between glaciers and rock debris supply in a mountain landscape domain, ((Figure presented.)), are described. Decimal latitude-longitude [dLL] geolocations are used to identify features and transects in an information landscape. Geo-located features are coded, enabling transects between a 1976 expedition and 2019 Google Earth imagery to be compared. Rock debris is progressively added to 1-3 km long glaciers which become debris-covered. Cirque glaciers eventually assume rock glacier (RG) forms when supraglacial debris loads are high. Some rock glacier snouts reach main valley floors and still advance over meadows. This behaviour is attributed to high geomorphic activity producing rock detritus and transport to glaciers in the early Little Ice Age. The advances of rock glacier snouts are a consequence of thinning; low-angle glaciers still moving beneath debris-covered glaciers (GLd) covers. Persistent melt pools continue to develop within the surface debris cover of glaciers and rock glaciers and expose glacier ice. All the rock glaciers are below the regional snowline and permafrost can be discounted for rock glacier formation. Scree slope (SS) development may ultimately be sufficient to cover bare glacier ice moving from a glacier (GL) to debris-covered glacier (GLd) to rock glacier (RG). Reverse slopes in the debris at the foot of screes mark the mass continuum of glacier flow below the debris cover, not the ‘rooting zone’ of a permafrost-derived RG. Scree slopes themselves show no evidence of rock glacier-like flow. A simple glacier ice-debris transport continuum model is sufficient and necessary for rock glacier formation and flow.