Biophysical antecedents:

Easter Island is located in the oriental end of the Polynesian area, in the South Pacific Ocean, in the Latitude 27° 9' South, and the Longitude 109° 27' West. It is to 3.700 km from the coast of Mainland Chile and 2.600 km of Mangareva in the Gambier Islands. This location confers it the characteristic of being one of the isolated inhabited insular lands in the world.

The island has a triangular form with an approximate surface of 16.600 hectares, each one of its sides possesses a distance of 16, 17 and 24 km respectively, being the maximum width of the island 12 km.

The climate of the Island is marine, of characteristic subtropical, temperate warm with rains the whole year. Altought of the great quantity of days with precipitation and that the cloudy average reaches at 2/3 of sky, the brightness is high and the number of hours of sun is very important. The relative humidity of the Island is similar even along the year (75% to 81% in the values monthly and 77% like annual average), reflecting the oceanic character there prevailing.

The annual average of precipitations for Easter Island is of 1.126 mm, with a variability of 31% about the half value, the maximum precipitation falls in autumn (30%), being May the rainiest month with 137 mm. In the rest of the stations of the year the precipitations is distributed in form relatively pair, what denotes the oceanic character of the climate. The driest average month is September with 73 mm.

The lowest value in the minimum stockings in Easter Island is 15,5°C and the highest value in the maxims stockings is 27,3° C. in spite of its oceanic character, the island shows an oscillation annual white of its thermal components.
The range among the temperatures higher and lower monthly stockings is 5,3° C; the annual half temperature is 20,7° C.


Volcanic geologic antecedents:
According to the above-mentioned you can point out that Easter Island is a volcanic island of oceanic type, of recent age, structured by a complex cycle eruptive that culminated with the development of several eruptive centers, those that, associated to the erosive processes of the sea, they gave him the morphological features that today presents.

It fits to point out that Easter Island, inside the global context of the tectonic plates, is bound to a line of high caloric flow, well-known as "Easter Hot Line" that cuts the ocean Pacific to the latitude of 27° S approximately. Also, they form this line other volcanic islands as Salas and Gómez, San Félix and San Ambrosio, the island Pitcairn toward the West of the line of the Pacific and numerous submarine volcanos that give continuity to this "hot line" toward the West.

The volcanic triangle constituted by Island of Easter rises to about 3.000 mt on the oceanic bottom, and its oceanic base has trapezoidal form, reaching dimensions of 130 km x 90 km x 60 km x 100 km, approximately; that is to say, their basal surface is almost 50 times superior to the surface of the island and given its slope, its body structures a typical oceanic volcanic shield.

Easter Island is formed, in general features, for three main volcanic centers: Poike, Rano Kau and Terevaka. Recent studies demonstrate the difference and complexity of the volcanic processes that have structured these centers, being the Poike that of simpler evolution and, in turn, the oldest, as they reveal it the ages absolute potassium-argon that oscillate among 3 million years and less than 300 thousand years. The Rano Kau follows whose activity is relatively contemporary with that of the Poike; their ages oscillate between 2,56 million years and 180 thousand years ago but contrary to the Poike it presents a more complex final phase, characterized by sourrer eruptions (rich in silica). it Suffered violent eruptions that culminated with the explosion that generated the collapse of the central cone, giving origin to the formation of the crater that today can be observed.

On the other hand, the Terevaka is the product of multiple eruptions Icelandic type that they control two systems of fractures of approximate direction N - S, from Hanga Roa until Puna Pau. It is considered that their last eruptive activity happened between 10 thousand and 12 thousand years ago, corresponding to the flow of lava of Hiva Hiva, in the Roiho area.
Other structures secondary volcanic exist in each one of these centers, as the eruptive line from Orito Mount To the Te Manavai crater, going by the the Rano Kau crater toward the Motu Kao Kao, Motu-Iti and Motu-Nui (3 small island in front of Orongo) and probably toward other submarine volcanic structures, to the SW of the island. Without a doubt this line controls the domes traquitic of the Poike and the cone of volcanic tuff in Rano Raraku.


Soils:
The soils of Easter Island are all of volcanic origin, either derived of ashy or insolent, thin or very thin lavas and with frequent blooming of lava. Most of they are covered with volcanic stones and fragments of lava, existing sectors where these materials are in great density (80 and 95%). For it, the series are by definition stony.In this case, it is considered that a floor is free of superficial stones, when these cover it between 10% and 15%.

The soils are in general loamy, product of a complete decomposition of the volcanic lavas in short periods; of this form, the fractions slime and clay they represent as minimum 60% and on the average, 80% of the mineral fraction, not being strange those in that these fractions represent 95%.

Almost all the soils present deficiencies of potassium and it is it also frequents a lack of soluble phosphorus.

The soils are moderate or strongly sour with a high content of organic matter, especially in the surface. The natural fertility is moderate to low and the good drainage what allows an appropriate development of the plants. Nevertheless, some cultivations present limitations without a special handling of grounds due to the scarce proportion of water of profitable rain because of the high permeability and the high evaporation.

A widespread process of erosion exists in the island, the one that has acquired characteristics of graveness in some sectors like the Poike, Maunga Tea Tea, and Rano Raraku and in the north sector of the volcano Rano Kau. The most important erosive agents are the rain and the wind, those that act in combined form.

Hydrography:
In the island superficial currents don't exist and the underground layers of water are to a lot of depth and with use limitations for their saline content. The only three deposits of superficial waters are in the craters of the volcanos Rano Aroi, Rano Raraku and Rano Kau.

The existence of layers raincoats to certain depths, the high permeability of the superficial floors and the abundant precipitations believe extensive phreatic layers that circumstantially appear as coastal slopes.

Other source of water used formerly by the islanders was the concavities of rocks receiver rain water (Taheta), the good known ones of which are the following ones: Vai A Tare in the plain of the Rano Kau, Vai A Repa in the Vaitea Ranch, Vai Utu Roroa in the first one of the three hills of Maunga Tea Tea and Vai A Are near to the Pérouse bay.