Old and recent processes in a warm and humid desert hypogene cave: ‘A’rak Na‘asane, Israel

Abstract

Recent environmental processes are studied in ʻA'rak Naʻasane Cave at the northern Judean Desert, Israel. The outer zone of the cave is heavily influenced by the outside environment through a large entrance, facilitating entry of air flow, fauna and humans, with minor caveforming modifications. Conversely, the inner cave sustains humid and warm conditions, favoring modifications by condensation corrosion of convective air flow, associated with deposition of popcorn speleothems at the lower parts of dissolution pockets. The warm humid air of the inner cave may be associated with an underlying thermal water table. Active condensation corrosion is decreasing, possibly because of gradual change in the cave microclimate, associated with falling water table and ventilation. Increasing connection with the surface is indicated by high collapse domes, rare flood invasion, and a large Trident Leaf-nosed bat community which spends the winter within the innermost parts of the cave. Bat guano supports bedrock corrosion and a rich invertebrate fauna, but humans preferred the outer parts of the cave, particularly for refuge during the second Jewish revolt against the Romans. Rare occasions of ancient human entry into the inner cave support this scenario by the small number of artifacts compared with the outer cave. Enigmatic small cairns in the largest inner hall were probably erected during the Intermediate Bronze Age. confined cave, cave microclimate, condensation corrosion, bat guano, popcorn speleothem

The Contribution of Condensation-Corrosion in the Morphological Evolution of Caves in Semi-Arid Regions: Preliminary Investigations in the Kyrenia Range, Cyprus

“…6). Since the ceiling channel is carved into massive recrystallized carbonates, where few fissures are visible and seepage could only occurs during winter season, most of the water during late-spring and summer seasons is expected to come from condensation only (Frumkin et al 2018). Therefore, the curtains along the overhanging wall would mainly be fed by moisture originating from the ceiling channel.…”

“…In the First Chamber, convection loops make local condensation-corrosion that carves the rising channel located at the end of the chamber and on the breccia zone. Due to the complex distribution of convective loops, this corroded breccia is surrounded by an evaporation zone delimited by a popcorn line (Frumkin et al 2018). This results in evaporation of the moisture from the condensation zone (Fig.…”

“…In the Bottom Chamber, the permanent moisture cannot be related to the epikarst seepage, especially in the dry season. This moisture would results from the presence of the bat colony releasing vapour, together with heat and CO 2 , which are distributed by the local convection cells (Lundberg & McFarlane 2009Frumkin et al 2018). Moreover, the mineralization of guano releases acids (carbonic, nitric, phosphoric, and sulphuric) that strongly contribute to the aggressiveness of condensation water.…”

“…After the wall corrosion and gradual saturation, produced water flows along walls and produces calcite precipitation such as the curtains of Smoky Cave. Due to the apparent absence of dripping from epikarst seepage through the massive recrystallized carbonate rock, some of the speleothem's late evolution could be related to condensation-corrosion (Frumkin et al 2018).…”

“…In some peculiar cases, bat-related condensation-corrosion appears to be the main process of cave enlargement (Lundberg & McFarlane 2012. The morphologies related to this process are cupolas, bell holes, flutes, megascallops, pendants, karrens, ceiling channels, corroded or weathered walls, boxwork, and potholes (Cigna & Forti 1986;Jameson 1991;Tarhule-Lips & Ford 1998a, b;Auler & Smart 2004;Lundberg & McFarlane 2009;Miller 2014;Fabbri et al 2017;Frumkin et al 2018;Audra et al 2016 and references therein).…”