Spatial Inventory of Landforms in the Recently Exposed Central Highland of Sub-Antarctic Marion Island

Abstract

Until recently, the Central Highland of sub-Antarctic Marion Island (above 750m a.s.1.) was covered by snow. Climatic amelioration is deemed responsible for the disappearance of the former permanent snowline which had a lower altitudinal limit of approximately 650m a.s.1. during the early-1950s. The recent sub-aerial exposure of this area now enables the geology and geomorphology to be documented. Mapping incorporated air-photo interpretation and field surveys using a hand-held Global Positioning System (GPS) to ensure spatial accuracy. Most grey lava outcrops above 750m a d . exhibit some evidence of previous glaciations whereas black lava flows show no evidence of the effects of glaciers and must, therefore, post-date the Last Glacial Maximum (LGM). Frost processes currently predominate in the Central Highland, but there is a conspicuous lack of periglacial landforms (i.e. patterned ground) in scoria and grey lava areas. With the exception of thermal contraction cracking at one location, no other evidence for the development of geomorphological landforms in black lava areas exists. Other geomorphological landforms include meltout features, a manifestation of landscape process responses to climatic amelioration, mass movement landforms and the emergence of rudimentary aeolian landforms. Receding snow cover may enhance frost and aeolian processes, which could result in an interesting myriad of geomorphological landforms.

Diagnostic criteria for pronival ramparts: site, morphological and sedimentological characteristics

“…The criterion ‘Ridge size increase with distance from cliff foot’ used by Hedding et al . () and Brook and Williams () is discarded because the retrogressive genesis of an actively accumulating rampart on sub‐Antarctic Marion Island (Hedding ) indicates that size does not necessarily increase with distance from cliff foot. Rather, rampart size is dependent on debris production and snowbed size and shape, thus ridge size cannot be regarded as diagnostic.…”

“…Hedding et al (2010) dropped the criterion 'Crenulate or lobate plan form of outer margins' tabulated by Hedding et al (2007) but it is reintroduced here as a valid criterion for the identification of protalus rock glaciers (White 1981;Wilson 1990). The criterion 'Ridge size increase with distance from cliff foot' used by Hedding et al (2010) and Brook and Williams (2013) is discarded because the retrogressive genesis of an actively accumulating rampart on sub-Antarctic Marion Island (Hedding 2008) indicates that size does not necessarily increase with distance from cliff foot. Rather, rampart size is dependent on debris production and snowbed size and shape, thus ridge size cannot be regarded as diagnostic.…”

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

“…The higher the amount of snow cover, the higher the average interpolated R values. Low R values observed for areas of less snow cover could indicate that the loss of the insulating effect of snow results in a more dynamic weathering environment, as suggested by Hedding (2008). These surfaces also exhibit a more dynamic temperature regime, as opposed to surfaces covered by snow/ice, which exhibit a more stable thermal regime (Gardner 1992;Hall and André 2001).…”

High-frequency monitoring of stream water physicochemistry on sub-Antarctic Marion Island

“…The island, situated in the Indian sector of the Southern Ocean, consists of a peak of a shield volcano. The island has an area of ± 293 km 2 and with its highest point (Mascarin peak) at 1 240 m amsl (Hedding, 2008). The island's climate is strongly influenced by its hyperoceanic position within the westerly wind belt (Rouault et al, 2005).…”