Undersea springs may have been crucial for the survival of the people who built the massive stone statues for which Rapa Nui – also known as Easter Island – is famous. Their ancient settlements and the platforms on which the monolithic statues were placed were all located on the coast close to such springs, surveys have shown.
These sources of fresh water were critically important, allowing Rapa Nui communities to survive long droughts, said at Binghamton University in New York during a virtual talk at the . “The environment is really marginal.”
The island gets a lot of rainfall on average, but it is unpredictable and there are often droughts. The only sources of fresh water are three small lakes, but these are far from settlements and dry up during long dry periods.
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This that places along the shore where groundwater flows out into the sea were vital to the island’s inhabitants throughout history.
These springs are a result of rainwater sinking through the porous rock and forming a freshwater layer on top of saltier, denser water below. During low tide, some of this fresh water flows out of the rocks into the sea in places.
“I have tried drinking the water,” DiNapoli told New Scientist. “In some locations, it is quite fresh, whereas in others it is quite brackish.”
There is already evidence that these springs were used by the Rapa Nui people, whose Polynesian ancestors settled on the island in around AD 1150. From the time the island was first discovered by Europeans in 1722, there are many historical accounts of locals drinking “seawater”, with the visitors apparently not realising the water was almost certainly fresh.
There are also ancient wells built right next to the shore to capture this water just before it reaches the sea.
Now, DiNapoli’s team , as it is known, by testing water samples and using drones with thermal sensors. The groundwater shows up as blue in thermal images because it is cooler than the seawater.
The surveys were done during a multi-year drought when two of the island’s lakes were dry. The springs were still discharging a fairly large amount of water.
The findings show that the location of submarine springs appears to have been the most important factor determining where settlements and ahus – the platforms on which the moai statues were placed – were built, said DiNapoli.
This same pattern was found even on the north-west coastline, where people would have had to descend steep sea cliffs to get to the water.
