Physical and Environmental Characteristics based Classification of the Caves of the Andaman Islands

‘Speleogenesis’ is the process of origin and developmentof caves in lithif ied rocks formed of aggregates of particulate matter (Ford & Cullingford, 1976), determined by the original sediment character and diagenetic history (Challinor, 1967). According to Ford & Cullingford (1976), sedimentary rocks are composed of the remains of plants and animals secreting calcium carbonate during their metabolism, which form the bulk of limestone. Variations in the composition of limestone are due to geochemical and cellular processes. Limestone karsts (a landscape formed from the dissolution of soluble rocks) consist primarily of calcium carbonate formed by calciumsecreting marine organisms millions of years ago before tectonic movements lifted them above sea level (Clements, 2006). Over the years, mechanical and chemical weathering exposes the karsts.Which usually, gives rise to the tower karsts and sinkholes (a hollow in a limestone region thatconnectswithacavernorpassage) or the cockpit karsts (a landscape of star-shaped hollows surrounded by steep, rounded hills, found in tropical karsts) (MacKinnon, 1996). Poulson & White (1969) def ined caves as human enterable cavities on earth (> about 0.6m in width). As per Bunker & Holt (2003), caves must be large enough to get the surveyor fully into the cave, turn around and exit without damaging the attached f lora and fauna. According to Howarth (1983), the subterranean habitat, which is f illed either by air or water, can be classif ied arbitrarily by size as ‘microcavern’ (<0.1cm in width), ‘mesocavern’ (0.1 – 20cm) and ‘macrocavern’ (>20cm). Studiesof karstgeometricproperties have shown that they approximate fractals, displaying a degree of self-similarity at all scales (Verbovšek, 2007; Curl, 1999). The scalar phenomenon, which also appears to be physically true in nature as many ways that scale dependencies could affect the geological processes involved in speleogenesis (Max, 2008). Depending upon the climate, rock strata and biotic factor, caves can vary in size (Howarth, 1983), from few meters to more extensive systems, which extend to hundredsof meters intotherock. Caves are functional units consisting different species with various levels of specialization and ecological processes that depend on fundamental ecological process and othersdirectlyconnected to theexternal environment (Poulson &White, 1969). In the absence of natural light, cave ecosystem depends on the organic materials that fall, wash, wander, or is otherwise brought into caves (Poulson & White, 1969, Peck, 1974; Biswas, 2009). Terrestrial cave community depends on the availability and spatial distribution of the resources (Ferreira , 2007). With the limited available and supply of the resources, caves provide subterranean habitat for many species, some of which are wholly dependent on caves for life. Cave et al. The objective of the study was to classify the caves in the Andaman Islands, on the basis of their existence, rock layer type, cavesize, caveopenings (number, size, and shape) and the presence of light zones inside. All the 314 caves visited on 27 Islands were of limestone, dominated by Archipelago and Flysch group of rock layers. More than 60% caves are of small size, located in inland forests, below the ground, which lead to downward length from the opening. Around 86% caves had a single opening. We found the cave size varied with the rock layer type, vegetation type and a number of openings. Multiple regression models with differentvariables showed the type of rock layeras the most influencing factordeciding thecavesize in the Islands. This exploratorywork, asa baseline study, isa furtheraddition to the knowledge on the scarcely studied hypogene caves in theAndaman Islands.