Hydrogeology of Norfolk Island, South Pacific Ocean

Norfolk Island in the southwest Pacific Ocean has an area of 35 k m2 and rises to an altitude of just over 300 m. It is an erosional remnant of a volcanic complex consisting of subaerial basaltic lava flows and pyroclastics built on a submarine pile of hyaloclastite deposits and pillow lavas. A deep weathering profile has developed in the volcanic succession since eruptive activity ceased during the late Pliocene 2.3 Ma ago. Throughout the island there is an upper water table aquifer in porous alluvium and weathered basaltic rock. At the base of the weathered profile groundwater moves towards sea level through a complex network of fractures and other interconnected openings in volcanic bedrock. Semi-confined aquifers occur in fractured basalt flows and interbedded basaltic pyroclastics (tuffs and agglomerates). However, the extent and quality of deep groundwater below sea level needs more evaluation. The groundwater storage on Norfolk Island is tapped by more than 450 wells and bores.