Rising sea levels 6,000–8,000 years ago submerged the river valleys in Double Haven, leading to the formation of indented shorelines with headlands and bays. But the mountains in the area were mostly formed some 160 million years ago, when lava mixed with volcanic ash formed rock strata. Later, rivers flowed down from high mountains and washed sand and stones to coastal lowlands, forming reddish sedimentary rock about 500 metres thick. Popular landforms here include Hung Shek Mun, Camp Cove and Double Island.