Internal structure and permafrost characteristics of the rock glaciers of southern carpathians (romania) assessed by geoelectrical soundings and thermal monitoring

Abstract

Six rock glaciers in the Southern Carpathians have been investigated by means of geoelectrical soundings in order to detect their internal stratigraphy and the existence of frozen sediments. In the case of three relict rock glaciers, the electrical resistivity measurements indicated a typical internal structure. Low resistivity values (<10 kΩm) which are typical of unfrozen fine‐grained materials were obtained, but high resistivity values (25–240 kΩm) measured in the Pietroasa, Ieşu and Pietrele rock glaciers denote the presence of sediments cemented by interstitial ice and ice lenses. Based on the moderate resistivity values, the ice content is probably low to medium in the upper portion of these rock glaciers, that is, above 2040 m. At two sites (Pietroasa and Văiuga rock glaciers), ground surface temperature (GST) evolution was monitored using digital dataloggers. Mean annual ground surface temperature and GST regime throughout the winter were extracted from the recordings and confirmed the probability of permafrost occurrence in Pietroasa rock glacier. In the Ieşu and Pietrele rock glaciers, measurements of bottom temperatures of the winter snow cover were performed in March 2012. Considering the thick active layer, the reduced ice content and the presence of scarce vegetation on their surface it could be assumed that the permafrost exists in marginal conditions in the Southern Carpathians. The ground ice in permafrost is produced by the groundwater freezing or by snow banks buried by coarse angular boulders following large rockfalls.

Groundwater flow and storage processes in an inactive rock glacier

“…The rock glacier is underlain by quartzite bedrock at depths up to >30 m. The bedrock surface has low resistivity (<3,000 Ω·m), indicating the presence of water‐saturated material. Alpine geophysical surveys have similarly observed relatively low resistivities at the base of coarse sediments in rock glaciers (e.g., Evin & Fabre, ; Fisch, Fisch, & Haeberli, ; Ikeda, ; Merz et al, ; Onaca, Urdea, & Ardelean, ), whereas borehole drilling has shown an unfrozen layer of sediments above the bedrock interface in some rock glaciers (Arenson, Hoelzle, & Springman, ; Krainer et al, ; Maurer & Hauck, ). Consequently, it is hypothesized that a saturated zone exists at the interface between the rock glacier and bedrock, which may be within finer sediments over bedrock, or within intensely fractured and weathered rock overlying competent bedrock.…”

Short-term geomorphological evolution of proglacial systems

“…A C C E P T E D M A N U S C R I P T Langston et al, 2011;McClymont et al, 2011) and rock glaciers (Maurer and Hauck, 2007;Ribolini et al, 2010;Monnier et al, 2011Monnier et al, , 2013Monnier et al, , 2014Onaca et al, 2013, Seppi et al, 2015. Both ice-cored moraines and rock glaciers can be considered as composite and transitional landforms as relicts from former glaciation (cf.…”

Rock glaciers in Daxue Shan, south-eastern Tibetan Plateau: an inventory, their distribution, and their environmental controls

“…into active, inactive, and relict types (Sattler et al, 2016). In general, the presence of ice within active and inactive rock glaciers is indicated by a steep (> 35 • ) frontal slope (Ikeda and Matsuoka, 2002), a well-developed flow-like morphology defined by sets of parallel and curved ridges separated by long v-shaped furrows (Barsch, 1996;Roer and Nyenhuis, 2007), and an absence or sparse occurrence of vegetation (Onaca et al, 2013). Inactive rock glaciers also contain ice but are immobile.…”