Within Ta'a Oa are Atuona Bay and adjacent Taha Uku which are the best anchorages on the island. Hiva Oa is separated from the nearby island of Tahuata to its south by a wide channel called Ha'ava or the Canal de Bordelais. Climate Temperatures in the Marquesas are stable year round, but precipitation is highly variable. Precipitation is much greater on the north and east (windward) parts of the islands and much less on the western (leeward) parts. Droughts, sometimes lasting several years, are frequent and seem to be associated with the El Niño phenomena. The highest annual rainfall recorded in Atuona is ; the lowest is . Geology The island is of volcanic origin. Geologically, Hiva Oa belongs to the Marquesas Linear Volcanic Chain, which formed from a hot spot on the Pacific Plate and is moving west-northwest at a rate of 103 to 118 mm. per year. The magmatic rocks on the island are between 1.63 and 4.26 million years old, but volcanic activity has not yet been completely extinguished. Not far from the road from Atuona to Taaoa, further west, some mud pots and small solfataras can be seen. Flora Like Nuku Hiva, Hiva Oa, as the second largest island in the archipelago, has a relatively high biodiversity for the South Pacific islands. A total of 205 native plants - 24 of them endemic - and 178 exotic species have been identified. Among the richest and most widespread native species on the island are ferns with a high number of endemic species. They cover large areas of the inaccessible, humid and shady incises of the valley. Among the idiocorophytes (ancient autochthonous species) are probably the coconut palm and the screw tree, which are widespread in the lowlands. Anthropochorophytes, such as breadfruit trees and Tahitian chestnut (Inocarpus edulis), already introduced by Polynesian settlers, predominate in the lowland and midland regions. A threat to native plant communities could be bamboo, which is not native to the island and has already formed extensive groves in some places. In the higher, more inaccessible areas of the island, the natural habitats remain almost unchanged. The north, shaded from wind and rain by the mountains, is largely arid. Fauna The fauna of the Marquesas Islands is limited to land and sea birds, insects, reptiles, butterflies and spiders. The Marquesas warbler (Acrocephalus mendanae mendanae) is endemic to Hiva Oa and the neighboring island of