The geology of Hoàng Liên National Park includes metamorphosed sediments and a granitic intrusion. The metamorphosed sediments strike from north-west to south-east along the Muong Hoa valley. On the north-eastern side of the valley is a craggy ridge of marble and metamorphosed carbonate rocks that exhibit a karst style of weathering. These formations are currently being quarried for road building. The valley floor is characterised by schist and, to a lesser extent, gneiss. The granitic intrusion extends from the Muong Hoa River to the summit ridge of Fansipan and beyond. Due to the high humidity and rainfall in the area, chemical weathering is prevalent. This is reflected in the clay nature of the soil.