Evidence for Headwall Weathering Zones, Boundary Glacier, Canadian Rocky Mountains

Abstract

ABSTRACT. Temperature records from several randklu/t sites at the margins and headwall of Boundary Glacier (Iat. 52°12'N., long. 117°12'W.) in the Canadian Rocky Mountains are presented. These records indicate that during the ablation season a diurnal freeze-thaw air and rocksurface temperature regime occurs in a 2 m wide zone centred on the randklu/t lip. Deeper in the randklu/t , stable sub-zero conditions prevail whereas above the randklu/t an above-freezing temperature regime prevails. The freeze-thaw temperature regime, observed freezing of melt water and rain water on randklu/t rock surfaces, and copious in-situ loose weathering products on the head wall and marginal free faces suggest an active frost-shattering environment. Downslope migration of the randklu/t lip during the ablation season results in a migration of the freeze-thaw zone and thus a seasonal extension of the rock surface area exposed to the favorable weathering environment. Longer-term glacier fluctuations, with attendant thinning and thickening of the ice body, could result in large areas of marginal and headwall rock surfaces being exposed to the randklu/t weathering environment over long periods of time. The data and observations from Boundary Glacier support an idea, suggested by Battle (1960), that open and shallow randklu/ts, rather than closed and deep bergschrunds, are a focus of weathering at glacier margins and thus a potential factor in cirque development.

Glacial cirques as palaeoenvironmental indicators: Their potential and limitations

“…In addition to the abrasion and quarrying described above, periglacial processes (predominantly freeze-thaw) are important erosional agents at cirque lateral margins and at the base of the cirque headwall (which becomes progressively more exposed during the ablation seasons due to the widening of the randkluft) (Gardner, 1987;Sanders et al, 2012). Such processes play a key role in the subaerial retreat of cirque head and lateral margins (Embleton and King, 1975;Sanders et al, 2012), and removed material accumulates at the base of slopes, either on the surface of the glacier or at the glacier bed.…”

ACME2: An extended toolbox for automated cirque metrics extraction

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Aspect‐controlled weathering observed on a blockfield in dronning maud land, antarctica

“…A number of studies (e.g. Whalley ; Gardner ; Hall ; Shakesby et al . ) have considered the dual effects of solar radiation directly impacting rock temperature regimes, as well as driving moisture availability and concomitant disintegration/decomposition.…”

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