Along with the highest elevations of Phosphate Hill and Flying Fish Cove, the rocks from Murray Hill summit are characterized as dolomitic limestones, containing between 34 and 41 percent carbonate of magnesia. Analyses of the rocks has shown that the fossils are mostly obliterated, though there are remains of foraminifera, Lithothamnion, and possibly coral. The small, brown spherules of phosphatic matter which occur on the hill in a bed of rock may be explained because of phosphatic fossilization of volcanic rock. Murray Hill has an outcrop of many rocks subject to weathering. Recent 40Ar/39Ar geochronology study by Taneja et al. (2015) on the volcanic rocks from Christmas Island have shown that the experienced a renewed volcanism in the Eocene (43 - 37 Ma) and then a minor phase of volcanism in the Pliocene (4.2 Ma). Ecology The plateau around the summit is dense and evergreen, although the biodiversity of trees is limited compared to similar areas of continental rainforest. One of the main fauna is the red land crab, Gecarcoidea natalis, which feeds on small seedlings. Vertebrates include geckos such as Cyrtodactylus and Lepidodactylus listeri, and skinks, specifically the Cryptoblepharus egeriae (Blue-tailed Skink), and Emoia nativitatis (Christmas Island forest skink); major invertebrates are also present, such as the robber crab, and the little nipper Geograpsus grayi. Murray Hill is an integral part of a reserve area which covers the entire southwest corner of the island. Initially, it was declared as the Christmas Island National Park declared by Proclamation under the National Parks and Wildlife Conservation Act 1975, on 21 February 1980, covering an area of 85 km2 (out of total area of 135 km2 of the island). On 16 July 2000, the Environment Protection and Biodiversity Conservation Act 1999 came into effect and the park is now a Commonwealth Reserve under this Act. As of 2010, the national park makes up 63 percent of Christmas Island. References External links Murray Hill, Christmas Island, GeoNames. Geography of Christmas Island