Ly Son Island structural rocks which have the late Holocene age are divided into five categories from young to old stratigraphic units, including 1) the recent marine deposition (Q2^3.f), 2) marine sediments of the first terrace (Q2^3.e), 3) flow basalt (Q2^3.d) and pyroclastics (Q2^3c), 4) calcarenite (Q2^3b) and 5) coral reef rock (Q2^3a). Ly Son geomorphology is characterised by: high up cinder cones in the island have funnel mouth, and basaltic flow forms a low cover at the foot of volcanoes; marine terraces and beaches are mainly composed of calcarenite, and coral reef rocks are distributed around the island. Significant destruction of marine waves into the volcanic slopes and basalt flows forms interesting landforms along the island such as sea cliffs, sea caves, rocky coasts, stone towers, etc, the most attractive of which is the Hang Cau - Chua Hang cliff where reveals a volcanic structural cross-section and stratigraphic relationship between pyroclastic rocks overlaid on calcarenite layers.