This study characterizes how changes in climate may alter the physical and chemical properties and the reaction kinetics of the extraordinary manganese soils found in Graskop, South Africa. Manganese-oxides govern many geochemical reactions due to their abundance and high reactivity. Despite their importance in cycling redox sensitive compounds in natural systems, much remains unknown about the reactivity of manganese-oxides formed under environmental conditions and how this may be altered by changes in local climates. In order to study how these manganese-oxides react, soils were collected from Graskop, South Africa. Three soil profiles were excavated with a range of manganese concentrations. Each profile was further separated based on horizons, with some of the profiles containing over 20% manganese. Manganese nodules of various sizes are ubiquitous in these soils. The soil in each horizon was thoroughly characterized to determine chemical and physical properties, including cation exchange capacity (CEC), point of zero charge (pzc), Brunauer–Emmett–Teller (BET) surface area, and buffering capacity. X-ray powder diffraction (XRD) was used to characterize the mineralogy of the crystalline material found in the clay fraction. The nodules present in the soils were also analyzed and their crystalline composition was determined with XRD. Scanning electron microscopy (SEM) images were taken of each soil to characterize the particle distribution and minerology. A series of batch reactions were used to determine the capacity of these soils and nodules to oxidize arsenite into arsenate under a variety of factors that may be impacted by an altered climate. The conditions of the reaction were varied from pH 4.5, 7.2, and 9.0 and temperatures ranged from 4.5 ˚C, 23 ˚C, and 40 ˚C to elucidate how differing pH and temperature influenced the oxidation reaction. Aliquots collected from these experiments were analyzed by liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS). Solid samples from the reactions were taken to National Synchrotron Light Source II and analyzed on beamline 4-BM to determine the changes in manganese oxidation state after reacting with arsenite under varying conditions. X-ray fluorescence maps were collected on thin sections of these soil to analyze the distribution and speciation of Mn and Fe in natural soils and nodules. This study provides key insights to more fully understand the role of manganese-oxides in controlling redox sensitive reactions in the present and future environment.