Rapa Nui National Park: Nature
Rapa Nui is a triangular-shaped island of volcanic origin, created by the action of three main volcanoes: Terevaka, Katiki and Rano Kau. The island is actually the peak of an enormous submerged mountain with a circumference at its base of 200 kilometers (125 mi) and around 4000 meters (13,120 ft) in altitude.
The topography of the island is undulating, with smooth slopes and numerous volcanic cones, distributed across its surface.
On the island there is no surface running water and the underground water sources are found at a medium depth. The only three surface water deposits are on the Rano Aroi, Rano Kau and Rano Raraku.
Flora and vegetation on the island are scarce. In the prairies you can find Giant Rat's Tail Grass and koda millett, accompanied by shrubs of tropical guava, wild sunhemp, and bush lupine. There are also some forests, where the predominant varieties are Eucalyptus, Mellia azedarach and silk trees.
The native species are concentrated in several areas, one of which is the crater of the Rano Kau volcano, where you can see mako'l, mahute, ngaoho, hau hau and some ferns. In some places of Hanga Roa and in the vicinity of CONAF there are toromiro trees, an endemic species which CONAF is trying to reintroduce to the island's ecosystem.
Vegetal formations cover 90% of the island's surface, arboreal formation and plantations occupy 5%, bushes 4%, and the remaining 1% corresponds to very sparce vegetation in eroded areas, rocky places, and urban areas.
Forests and plantations: mainly Melia Azedarach and Albizia Julibrissen. Plus, there are several copses across the island, mainly formed by pikanos (Eucalyptus globulus). The structure of these copses is contemporary and monostratified, pure formations with no understory and with a herbaceous layer dominated by Here hoi (Sporobolus africanus). In the Rano Kau plantations, the endemic species mako'i (Thespesia pupulnea) has also been used, and in Anakena there is a small plantation of cocos nucifera, which are important for the their aesthetic value.
Scrubland: the bushy formations are not too varied, the predominant species being tuava (Psidium guajava), Crotalaria sp, chocho (Lupinus arboreus), vine, mahute (broussonetia papyrifera), and Dodonaea viscosa. The three latter species are located in Rano Kau, Lupinus arboreus in Hanga Roa, and Crotalaria sp. in Hotu Iti. Tuava (Psidium guajava) is the bush of largest distribution in the island. It is associated to a large number of species, most commonly the toroco herbs, here hoi, heriki hare and Crotalaria sp.Prairies: according to Michea, the dominant species in the prairies is here hoi (Sporobolus africanus), which can be found on its own or sharing the habitat with other species. Heriki hare (Paspalum scrobiculatum) is also present in areas with low or medium altitude, where it is associated to the Sporobolus Africanus. In turn, Sporobolus africanus is present in high areas or Terevaka. Other important species are Erigeron linifolius, Euphorbia hirta, and Euphorbia serpens.
The laund fauna in Easter Island is not too diverse, unlike in other polynesic islands. Some important species are the small lizards called Gekkonidae Lepidodactylus lugubris (moko uru-uru kau) and Ablepharus boutoni poecilopleurus (moko uri uri). Occasionally you can find the green tortoise (Chelonia mydas) and carey turtle (Eretmochelys imbricata bissa). Important sea birds are kena (Sula dactylatra), tavake (phaeton rubricauda), makohe (Fregata minor), kakapa (Pterodroma arminjoniana), and kuma (Puffinus nativitatis). There are also small seagulls like the grey-backed tern and kia kia (gygis alba), which are part of the Tangata Manu tradition.
Geology and Geomorphology
Easter Island is a volcanic, oceanic island of recent age, structured by a complex effusive cycle, which culminated in the formation of several eruptive centers. These, associated to the eruptive processes in the sea have given the island its current morphologic traits. The main eruptive centers are Poike, Rano Kau, and Terevaka, the latter reaching 511 above sea level. The island has an undulating topography.
There are no superficial flows in the island, the underground waters are very deep, and cannot be used due to their high salinity. The only three water deposits are located in the craters of Rano Aroi, Rano Raraku, and Rano Kau.