Influence of Hillslope Aspect on a Cinder Cone Evolution: The Sandal Divlit example, Kula, Turkey

Abstract

Microclimatic variations in semi-arid ecosystems can cause topographic asymmetry over geologic time scales due to uneven distribution of incoming solar radiation as a function of slope aspect. This phenomenon has long been recognized in geomorphology and has been studied primarily in catchments with high spatial heterogeneity in climate forcing and underlying lithology. Due to fluctuations in prevailing climate and lithological differences in the studied catchments, the formation age and size of the catchments add another level of complexity and uncertainty. Due to their small size, uniform lithology, well-constrained initial morphology, and relatively young age, cinder cones are natural laboratories for better understanding the eco-hydro-geomorphic evolution caused by nonlinear interactions between vegetation, climate, and soil. The Sandal Divlit cinder cone located in the Kula volcanic field, western Turkey, is an inactive volcano and formed in the last stage of volcanism in the region. The climax vegetation in the primary succession following the volcanic eruption can be seen on north-facing slopes with trees. North-facing slopes have deeper soils than south-facing slopes, which have sparsely herbaceous plants and shrubs and thin, weakly developed soils. Airborne-LiDAR surveys and the digital elevation models having 5 m and 12.5 m spatial resolution were used to analyze the geomorphic descriptors and canopy structure of the cone as a function of aspect. In the summer and winter seasons, the surface temperatures of the cone were measured using a thermal-imaging drone. The results show that north-facing slopes are much cooler and have less evaporative demand than south-facing ones. As a result of denser vegetation attributed to relatively more available soil moisture, they are steeper than south-facing ones due to better erosion protection. Despite its young age (<30 ka), the cone has developed topographic asymmetry and is imprinted with the signature of aspect-related vegetation difference. This finding is further evaluated and with the results of landscape evolution models to assess the role of microclimate due to vegetation on the development of asymmetric geomorphological features.This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329. The financial support received from TUBITAK does not indicate that the content of the publication is approved in a scientific sense by TUBITAK.