GENERAL ARTICLE Khadg Singh Valdiya * Six Decades of Himalayan Geology and Environment (Life and Work) Sampat Kumar Tandon and Ananya Divyadarshini S K Tandon is currently an Adjunct Professor at IISER Bhopal with broad interests in Earth System Science including sedimentology, physical stratigraphy, quaternary geology, paleoclimate and tectonic geomorphology. Ananya Divyadarshini has been working on tectonic geomorphology, active tectonics, structural geology and quaternary landforms and processes since her PhD at the University of Delhi, and post-doctoral research at JNCASR, Bengaluru. Khadg Singh Valdiya, a stalwart amongst Indian geoscien- tists is widely recognised and highly respected for his pioneer- ing works on Himalayan geology and environment. Besides being a recipient of the highest Civilian Awards: Padma Shri and Padma Bhushan, he was the awardee of numerous prizes, awards, honours and fellowships [1]. His significant contribu- tions to the stratigraphic, structural and tectonic evolution of the Himalaya laid the foundation for several ongoing studies in the Himalaya. Valdiya also made noteworthy contributions to the tectonic rejuvenation of the central Sahyadri moun- tains, and the origin and disappearance of the prehistoric Saraswati river in northwest India. Valdiya wielded enor- mous influence on the Indian geoscience academic commu- nity through the many books that were authored by him on Indian stratigraphy, Himalayan geology, the Saraswati river, neotectonics of the Indian sub-continent, and environmental geology. Historical Overview K S Valdiya devoted nearly 40 years of his research career to in- vestigating the Himalaya, which is one of the most tectonically active orogenic belts of the world. The Himalaya are divided into four tectonic terrains from north to south, i.e., the Tethyan Himalaya, Greater (Higher) Himalaya, Lesser Himalaya and the Sub-Himalaya (Figure 1). These tectonic units represent distinc- tive physiographic and litho-stratigraphic zones at the northern edge of the Indian sub-continent. The northern limit of the Hi- * Vol.26, No.3, DOI: https://doi.org/10.1007/s12045-021-1134-z RESONANCE | March 2021 317