Tafoni development in a cryotic environment: an example from Northern Victoria Land, Antarctica

Abstract

Tafoni are a type of cavernous weathering widespread around the world. Despite the extensive distribution of the tafoni, their genesis is not clear and is still a matter of debate, also because the), occur in such different climatic conditions and on so many different types (if substrate. Geomorphological characterization of more than 60 tafoni in three different Antarctic sites (two coastal and one inland) between 74 and 76 degrees S with sampling of weathering products and salt occurrences are described together with thermal data (on different surfaces) and wind speed recorded in different periods of the year in a selected tafone close to the Italian Antarctic station. The aim of this present study is to provide further information to help understand the processes involved in the growth of tafoni in a cryotic environment, and the relationship of these processes to climate, with particular attention to the thermal regime and the role of wind. The new data presented in this paper suggest that there is no single key factor that drives the tafoni development, although thermal stress seems the most efficient process, particularly if we consider the short-term fluctuations. The data also confirm that other thermal processes, such as freezing-thawing cycles and thermal shock, are not really effective for the development of tafoni in this area. The wind speed measured within the tafoni is half that recorded outside, thus favouring snow accumulation within the tafoni and therefore promoting salt crystallization. On the other hand, the wind effect on the thermal regime within the tafoni seems negligible. While both salt weathering and thermal stress appear active in this cryotic environment, these are azonal processes and are therefore active in other climatic areas where tafoni are widespread (such as the Mediterranean region)

On the persistence of ‘weathering’

“…In many instances (frequently in the case of tafoni) while there is some understanding of the weathering involved (e.g. Strini et al, 2008) there is very little understanding of the removal processes. Yet, surely, the removal process is as vital to the landform creation as is the weathering, perhaps more so as it may exert further erosional or form-related effects?…”

Permafrost and snow monitoring at Rothera Point (Adelaide Island, Maritime Antarctica): Implications for rock weathering in cryotic conditions

“…Potential freeze-thaw 149 events (PFTE) were calculated as the number of times that daily or hourly mean temperature 150 crossed the threshold of 0°C divided per two (Strini et al, 2008). 151…”

Advances in permafrost and periglacial research in Antarctica: A review

“…Hall and André, 2001;Hall et al, 2008;Strini et al, 2008;Hall and Thorn, 2011). Moreover, the number of potential freeze-thaw cycles is only a few, at least in Continental Antartica, Strini et al, 2008;McKay et al, 2009). Within soils and deposits where water content is high, the potential freeze-thaw cycles can significantly affect the active layer dynamics, but their number may be highly reduced by the occurrence of cryptogamic vegetation (Guglielmin et al, , 2012b.…”

“…Hall and André, 2001;Hall et al, 2008;Strini et al, 2008;Hall and Thorn, 2011). Moreover, the number of potential freeze-thaw cycles is only a few, at least in Continental Antartica, Strini et al, 2008;McKay et al, 2009).…”