At Perdigões we have recorded 12 ditches. Seven of them were already surveyed in a section. Of course that we do not know if the dimensions of those sections “speak” for the entire perimeter of the ditches. We have evidence from other sites that a ditch volume and shape may change a lot along its perimeter. And Perdigões is not an exception. Ditch 12, the only one surveyed in two different areas, has a different shape and a different filling in survey 1 of Sector Q and in survey 2 of the same sector.
That shows us that we cannot generalize to a whole ditch what we observe in one section. But does not imply that, in general terms, we cannot try to approach the general picture.
For instance, Dicth 1 at Perdigões is a long one: it has a perimeter of almost 1,5 km. It was surveyed in a section near Gate 1, first by the ERA team and in the last few years by University of Málaga team (that is collaboration in the General Program of Research of Perdigões). It showed a “V” shape, with about 3 m deep and 7 to 9 meters wide. It allow us to calculate a volume for a one meter section: 9.61 m3. Multiplying this volume by the perimeter we get a volume of 14232 m3 and using the pattern wait of a m3 of diorite (around 2600 Kg) we have 37 000 tons of rock extracted, just for Ditch 1.
This can gives us an idea of the amount of work involved in Perdigões through its living time. And more interesting: once again, where is that amount of bedrock?
Ah! And do not forget that we have evidences of practices of re-cutting of some ditches after their first filling process. And that enlarges the amount of work that we can calculate to the recorded structures.
These big enclosures were huge public enterprises.
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