The river valleys in the Volhynian Upland have different terraces with varying ages and compositions. The Horyn River valley stands out with a fourth terrace, while others mostly have three. The highest terrace in the Horyn Valley formed in the Early Pleistocene, the third in the Middle Pleistocene, and the two lowest in the Late Pleistocene. The older terraces have thick loess cover and are more dissected, while the younger ones have thinner loess cover. The lowest terrace is sandy and uneven, with the floodplain having two distinct levels formed in the Holocene. Overall, the terraces in the Volhynian Upland show a complex history of formation and development.