The basalt mysteryTo carve the moai statues, huge amounts of rock had to be hacked away around each one of them. In theory, this work could have been done using the basalt picks that have been found in abundance at the Rano Raraku quarry – though no one in modern times has felt like demonstrating how a complete statue can be carved by such arduous and primitive means. The possibility that more advanced tools and methods were used at certain times for some of this immense labour cannot be ruled out.
Fig. 6.16 Is this how all the carving was done?1
Although the platforms are mainly composed of unworked basalt blocks, many have retaining walls made of skilfully cut and fitted blocks. Carving these slabs would have been a tremendous undertaking, and this also applies to the shaping and boring of the basalt hare-paenga foundation blocks, the carving of basalt statues, the cutting away of basalt to make the roads, and the carving of several thousand petroglyphs in relief on tough basalt rock. The working of basalt poses problems of an altogether different magnitude than the softer volcanic rock found at Rano Raraku. What tools were used for this purpose? And have any experiments been conducted to test the proposed methods, as in the case of statue carving, raising, and transportation?
John Flenley and Paul Bahn argue that although there are still plenty of ‘intriguing questions’ to be answered about Easter Island, there are no genuine mysteries, though that doesn’t stop them entitling their book: The Enigmas of Easter Island. Interestingly, the problem of working basalt does not merit a single mention anywhere in their informative but conservative book! When asked by email how the basalt was cut, John Flenley said he had no idea, and Paul Bahn replied: ‘a good question, and one which, I think, has never really been tried out with experiments. Obviously the basalt can only have been worked with stone of equal or greater hardness, which can only mean basalt from the island.’2
But as Macmillan Brown pointed out, most ahu blocks are ‘of a vesicular basalt that European masons would find hard to work even with tools toughened by admixture of the rare metals’. Believing however that the masons had nothing but clumsy stone tools at their disposal, he says that each of the scores of immense shaped stones, weighing from 2 to 20 tons, ‘must have taken a workman with his stone implements, aided by sand and water, years to cut and groove’.3 It seems unlikely, though, that such skilled work would have been undertaken with such patently inadequate tools. The reason no one has ever conducted any experiments to see whether basalt can be precision-cut using basalt tools is very simple: no one is dumb enough to even try!
The Poike ditch is a deep and possibly entirely artificial ditch separating the eastern headland from the rest of the island. Although largely filled with silt today, it has a rectangular bottom, 3.7 m deep, about 12.2 m wide, and is about 3.5 km long. The tough basaltic rock removed could easily have supplied building blocks for all the platforms on the island with cyclopean masonry. Ahu Tahiri, Ahu Tongariki, and many more platforms were constructed from blocks of black basalt of a similar type. The ditch was a considerable feat of excavation, and is unlikely to have been chipped out with small basalt picks!
After the initial excavation of the lower trench through the lava flow, a considerable period appears to have elapsed during which a layer of inwash from the surrounding area, at least 1.8 m thick, accumulated in the ditch. There is evidence that some time after the original cutting, partial reexcavation took place, but exactly when is unclear. Carbon dates obtained so far do not tell us when the trench was first excavated, only that it could have been no later than 200 AD – and possibly ages earlier.4
