The rock types of the Sathyamangalam Wildlife Sanctuary mainly belong to the great gneissic series of pre-Cambrian age. The common metamorphic derivatives found in the sanctuary are metamorphosed sedimentary rocks such as quartzite, hornblende, amphibolites, pyroxenites and Pyroxene. The quartzite consists of quarts with small amount of sericite and faschite nicaad feldspar. If magnesite forms an accessory, the rocks acquire reddish tinge (east of Sathyamangalam). The amphibolites and hornblende are dark coloured and occurs in the north east of sathyamangalam. Metamorphic igneous rock types such as biotic gneiss charnookites and granite gneiss have widespread occurrence. The charnoctices were bluish with grenary look and the most widespread in the hilly forests. The biotic gneiss comprises the narrow forest lands adjacent to slopes of hills overlooking the plains. The minerals found in the sanctuary are; feldspar, quartzite, magnetite, garnet, kynite.
The Soil is a dynamic layer of surface material which is constantly changing and developing under process of adjustment to condition of climate, parent material, topography, and vegetation. Soils are made up of substances existing in solid, liquid, and gaseous states. With colloidal particles of organic and inorganic origin playing an important function in their makeup and activity. The physical properties of soils often acquire greater importance than the chemical ones. In majority of the cases the chemical fertility may be adequate but the growth of trees differs widely in accordance with the physical nature of the soil.
The common soil types of the sanctuary are red soils, laterite soils, black cotton soils, and Alluvial soils.
Soil texture refers to the relative proportion of particles of various sizes. The usual classification is given below:
Course sand: 2- 0.2 mm diameter; Fine Sand: 0.2 – 0.02 mm; Silt: 0.02-0.002 mm; Clay: < 0.002 mm
The terrain is gently undulated in the Moyar Valley with elevation ranges from 960m to 1266m in the Bhavanisagar, Sathyamangalam Range, Talavadi, Talamalai and Hasanur Ranges. The western part of the sanctuary is almost flat.