The term 'CAVES, STUDY OF' is referred to as Speleology, which is a 10 letter word. Speleology is the scientific study of caves and other karst features, such as sinkholes, springs, and underground rivers. It involves the exploration and mapping of caves, as well as the study of their physical and biological features. Speleologists also study the history and geology of caves, and the effects of human activity on them.