The composition of beach sediments is derived from the available material in nearby areas and reflects the nature of material brought in from the nearshore or alongshore sources. Transport of sand in the surf and intertidal zone accounts for a significant volume of immediate sand supply. Erosion of the coast itself, reworking and shoreward movement of beach and nearshore material are also important sources of sand. The source of the coralline beach sand is the surrounding fringing reefs. Areas of reef development generally provide locally derived beach materials which include various biogenic carbonate grains that reflect the composition of living biota adjacent to the beach.
Fresh water is present in the form of shallow groundwater.
Lihiman has a land area of approximately 29 hectares, about the same size as Baguan. The circular portion at the northeast end was built up by the extrusion of a mud volcano. Compared to those of Boan and Bakkungan, the mud extrusion is relatively more violent and has created a 20-m crater at the hilly portion. Extrusion activity is said to be accompanied by tremors. Extruded material contains a mixture of mud and angular boulders.