The rocks of the Nallamala ranges belong to the Kadapa system which is a series some 20,000 ft. thick.The primary rocks are Quartzite overlaid with an irregular slaty formation. Some sandstone is also to be found. The rocks here are very irregular and soft in texture thus rendering commercial exploitation impossible. These rocks are among the oldest in the world and have been formed as a result of large scale volcanic activity hundreds of millions of years ago. The evidence of the volcanic forces are evident in the foldings into which the rocks have been forced, in some cases the folds have been completely inverted.
The Nallamalas have a rather warm to hot climate throughout the year. Rainfall averages about 90 cm and is concentrated in the months of the South West Monsoon (June–September). The fissured rocks prevent any water from percolating underground and hence most of the discharge runs off as mountain streams to join the Gundlakamma River, the largest river to arise in these hills. Winters are mostly cool and dry with the average temperature around 25 degrees celsius.