Volcanoes & Vegetation Easter Island

Introduction

Easter Island, like the Hawaian Islands in the northern Pacific Ocean, was created by underwater volcanoes. Further below we will explain the natural geography and estimated, historic timeline behind its creation.

Geographic Creation Easter Island

The Island was created by the eruption of undersea Pacific volcanoes around a period close to 750,000 years ago, with the last major eruption detected as being around 100,000 years ago (very young in geological terms) and, according to geologists, the most recent volcanic activity of any kind was 10,000 years ago, despite steam seen to be emitting from the walls of the Rano Kau crater in the early 20th century by the then Island “manager”.
 
These volcanic undersea eruptions rose from the ocean floor spilling molten lava all the way to the surface until breaching sea level, where a land mass in the shape of an almost perfect triangle, or some would say like a “boomerang”, was formed. The longest line of this triangle, point to point, is only 24km with the shortest line 12km wide, and the area covered is 166km2, reaching a height of 511 metres above sea level. There are no natural rivers or streams, but there are three fresh-water-filled volcano craters at Rano Kau, Rano Raraku and Rano Aroi.

There are three principal extinct volcanic craters that dominate the Island and largely responsible for its formation.

1 - Rano Kau Volcano (south-west sector of the Island)
This is the volcano at the south-western end of the Island, with the large, circular, water-filled crater next to Hanga Roa village.

2 - Treveaka Volcano (central sector of the Island)
The highest of the three is Treveaka, reaching a height of 511mt above sea level, positioned in the central, northern sector of the Island, forming the main bulk of the landmass.

3 - Poike Volcano (north-east sector of the Island)
The volcano called Poike occupies the north-eastern end of the Island whereupon its sides have been eroded by the ocean and high, volcanically-layered cliff faces can be clearly seen on the southern side.

Their combined volcanic slopes and lava flows combine to provide an undulating landscape covered in varying degrees of vegetation. At the lower levels the land is mostly covered in grass peppered with a continuous number of loose volcanic rocks. On the higher elevations, and sides of the volcano slopes, the terrain is a mixture of heath and moorland. Apart from a few isolated areas of foreign-introduced Eucalyptus trees, the Island is predominantly treeless.

Below, we will briefly explain a little about these volcanos mentioned above as well as some other volcanoes.

The Rano Kau volcano is the one with an almost perfectly conical volcanic crater that occupies the full south-east corner of Easter Island and is beside the airport, as well as Hanga Roa village. It is also the largest volcano on the Island.

The volcano rim, which is at 324m above sea level at its highest point, is accessible for walking around, whereupon the silence is only broken by the chirping of birds, wind, and sea breezes. The width of the water-filled crater, 200m below, measures 1.6km. The volcano is estimated to have last erupted around 180,000 years ago.
In the Rapanui language the word “Rano” means a volcano where water is contained. And the word “Kau” means a lot of water and very wide, therefore Rano Kau refers to a “wide volcano filled with water”, which it is.

The natural lagoon has an estimated depth of around 10m and is covered by naturally-formed reed islands that float on the surface, each island with a base of approximately 1m in depth. The potable water in the lagoon was a source of drinking water for the islanders until only a few decades ago.

Due to the height of the interior of the crater and the fact that there is an earthen slope down to the lagoon, rather than a vertical wall, it has been possible to plant various fruit trees and other plants in some areas that get protection from the wind as well as receive moisture from a microclimate created within the crater.

Located adjacent to the crater rim, on the ocean side, is the ancient ceremonial village of Orongo, and this is one of the key archaeological places to visit on Easter Island. See our Places of interest page

Reaching a height of 511 above sea level is the summit of Terevaka Volcano and this is the highest point on Easter Island from which there is an almost 360° panoramic view over the entire island. If it is a clear day and you are able to appreciate this view it usually generates an additional, perhaps overwhelming sensation of physically being surrounded by the immense Pacific Ocean and totally cut off from the rest of the World.

Experts say that Terevaka “surfaced” around 360,000 years ago, but unlike the two other “founding volcanoes” on the island there is no crater on Terevaka. This is due to its formation coming from numerous, smaller volcanic centres oriented in a north-south direction. The lava from this system created the main body of the Island and gradually joined the other two volcanoes together, resulting in the final triangular (boomerang shape) form the Island takes today.

The most recent evidence eruptions, around 10,000 years in the past, are to be found in the Roiho area and here is a small crater called Rano Aroi that contains a small lagoon covered over with totota reeds. This is the third freshwater reserve on Easter Island.

Occupying a full corner of the eastern corner of Easter Island is Poike Volcano. This volcano is known to be the oldest on the Island and the area around it is therefore the first part of Easter Island to have been created. In the language of Rap Nui “Po” means “night” and “ike” means “break”, as in “a place where night breaks”, in other words “the dawn” and this hill is the first place on the Island to receive the sun’s rays at sunrise.

It has been estimated that the Poike Volcano, emerged from under the sea around 750,000 years in the past. Then, around 300,000 years ago the two other key volcanoes Rano Kau and Terevaka emerged, and lava flows connected all three volcanoes together, basically forming Easter Island as we know it.

The Poike crater is circular and measures about 150 across and 10m deep and totally dry, where a small wood of eucalyptus trees grow. At its summit the volcano reaches 450m above sea level, with a gentle, conical slope occupying an area of 3.5km at its widest point and covered mainly in wild grass. However, the southern side of the cone ends abruptly where it meets a 100m-high cliff face, caused by the constant erosion by the Pacific waves.

On the northern face of the Poike Peninsula there are three lumps or mounds caused by the accumulation of a white stone called Trachyite, which is harder than the surrounding lava stone, and this was used to create the eyes in many of the Moai’s.

In an order going from the coast and then inwards the names given to these “lumps” are:
Ma’unga Parehe (broken hill)
Ma’unga Tea Tea (white hill)
Ma’unga Vai a Heva (magic water hill)
The three “lumps”, or mounds, can be seen very clearly on the northern slope of the volcano.

Rano Raraku Volcano (the Moai Quarry “factory”)

The Rano Raraku Volcano is the place where the Moai Statues were crafted out of the rock.

The quarry wall measures around 800m in length, and within it are a number of vacated, horizontal spaces from where other Moai’s were carved from prior to being moved to an “Ahu” (a mound upon which the Moai’s stand). Having said that, still evident today are a few Moai’s half-finished and lying horizontally in the rock face.
Then, scattered around in front of the cliff are the finished Moai’s in various upright, angled and lying down positions, but in the general area 367 have been counted.

For many this is one of the most fascinating archaeological locations on Earth.

The quarry is located 20km northeast from Hanga Roa, close to the Poike Volcano peninsula and only 1km inland from Hanga Nui Bay. It is also about 1.5km from the Ahu Tongariki with 15 Moais.

Some interesting points about this volcano are that it used to be called “Maunga Eo”, which means “perfumed hill”, due to an aromatic plant that grew in the area. Also, at the crater of there is a break in the rim whereupon it is clear to see the different volcanic soil types.

Rano Raraku Volcano was created around 300,000 years ago, say the geologists, and its crater rim reaches a height, above sea level, of 160m on its southeast side. The shape of the inner crater is elliptical, with a diameter of 700m, and within this area is a lagoon filled with fresh water with depth of around 4m.

Over 800 Moai’s have been counted on Easter Island and practically all of them originated from the rock here at Rano Raraku Volcano. Rock that, due to its creation through a mixture of lava, high temperatures, salt water, and huge pressures proved to be the raw material required for the fabrication of the statues.

The Moai’s here and all over Easter Island have created a mystery. No one really knows why they were sculptured, and how. Yes, there are a number of theories, but they are just that – theories, just like the theories surrounding the construction of the pyramids in Egypt.

But the main mystery is how the vast, incredibly heavy Moai Statues were transported to their final locations on the Ahu’s around the Island and when there, how they were placed in the upright position. And, in addition to that mystery is the question as to how they manged to place the also, incredibly heavy, red “hats” on top.

We prefer not to publish here all the theories, because they are just that, people’s ideas only and mostly they are highly unrealistic.

However, one thing is for sure. For those who come to the quarry, there is a kind of instant calmness, a silence and stillness and this atmosphere, together with the actual statues creates a unique, mystical experience.

Vegetation on Easter Island

Sub-Tropical Forests
It is said that there has never been much vegetation on Easter Island. This, however, was not always the case. Ecologists have discovered that Easter Island, together with its closest neighbour, the tiny island of Isla Sala y Gomez 415 kilometres further east, is a distinct eco region of Rapa Nui subtropical broadleaf forests. Botanical studies of fossil pollen and tree moulds left by lava flows indicate that the island was formerly forested, with a range of trees, shrubs, ferns, and grasses, but unfortunately the original subtropical moist broadleaf forests are now gone.

Palm Trees
Fossil evidence shows that there used to be a tall Rapa Nui palm tree (Paschalococos disperta) related to the Chilean wine palm (Jubaea chilensis), which was one of the dominant trees of the Island. It is assumed that like its Chilean counterpart it probably took around 100 years to reach its full height. Research has shown, too, that the Polynesian rat, which the original Polynesian settlers brought with them, influenced the disappearance of the Rapa Nui palm. Rat teeth marks can be observed on 99% of the nuts found preserved in caves or excavated at different sites, indicating that the Polynesian rat impeded the palm's reproduction. That, together with the fact that palms were cleared to make the settlements, led to their extinction almost 350 years ago.

Toromiro Tree
Another tree, the Toromiro tree (Sophora Toromiro) was prehistorically present on Easter Island and is now extinct in the wild. However, the Royal Botanic Gardens at Kew in the UK, and the Gothenburg Botanical Gardens in Sweden are jointly leading a scientific program to reintroduce the Toromiro to Easter Island.
 
With the palm and the Toromiro trees gone, rainfall was significantly reduced as a result of there being less condensation over the Island. Sheep farming also changed the biodiversity of the Island when grasslands were cultivated for sheep grazing.
 
Deforestation
It has also been argued, whether or not, the native Rapa Nui’s deforested the island in the process of transporting and then erecting their Moai statues as well as using trees to provide fuel, building materials and creating agricultural land for an overpopulated island. Experimental archaeology has demonstrated that some statues certainly could have been placed on "Y" shaped wooden frames called “miro manga erua” and then pulled to their final “Ahu” destinations. Other theories involve the use of "ladders" (parallel wooden rails) over which the statues could have been dragged. Rapa Nui traditions metaphorically refer to powerful spiritual power (mana) as the means by which the Moai were "elevated" from the quarry.

Totora Reeds
In the water-filled volcanic craters of Rano Kau and Rano Raraku there are Totora reeds (as found in the high lakes of the Andes) which suggested a South-American origin of early settlers, but pollen analysis of lake sediments shows these reeds have grown on the island for over 30,000 years, well before the recorded arrival of humans. 
 
Easter Island has suffered from heavy soil erosion in recent centuries, perhaps aggravated by agriculture and massive deforestation. This process seems to have been gradual and may have been aggravated by the extensive sheep farming of the Williamson-Balfour Company throughout most of the 20th century.