Christmas Island National Park - Geology and Geography

Geology and Geography

Christmas Island consists of an uplifted limestone cap metamorphosed from coral reefs overlying more ancient volcanic andesite bedrock. The underlying seamount lies some 500 km (310 mi) southwest of Indonesia, and the isolation by the abyssal zone has led to endemism amongst the marine ecosystem. The park's boundaries extend 50 m (160 ft) beyond the low water line. Approximately 46 kilometres (29 mi) of the island's 73-kilometre (45 mi) shoreline is within the park limits.

Many stretches of the shoreline are marked by rock platforms, which are filled by wave splashes to create rock pools. Sea cliffs, up to 60 metres (200 ft) high in places, rise steeply from the sea and form a series of stepped terraces, the lower cliffs of which are higher and steeper. Soil on the island is generally poor, punctuated by limestone pinnacles, and tends to dehydrate during the dry season. The limestone is fractured and has created a substantial underground cave system. There are both water-filled and dry caves.

Christmas Island's two Ramsar sites, The Dales and Hosnies Spring, are contained within the park.