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1/12/13: Resistivity

We’ve tried two different methods of sub-surface testing at El Kurru this season (both thanks to Mohamed Abdel Wahab of the University of Dongola-Wadi Halfa). I put up some magnetometry images earlier—they were measures of magnetic anomalies under the ground surface, and we’re starting the long process of testing what some of them were.

Dr. Mohamed and his assistant Abdel Halim also did some resistivity measurements. This involves setting up a line of electrodes and passing current through them. Some areas of earth are more conductive, and some are more resistant, and these differences can relate to archaeological structures underground. One disadvantage of resistivity is that it’s much slower than magnetometry, so we ran this test only where there was a magnetic anomaly. One advantage of resistivity is that it gives readings at different levels underground, so it provides a kind of layer cake view.

Here is one of the resistivity charts from one of our grid squares…the darker, redder readings are more resistant, and the bluer readings are more conductive. Dry sand is often quite resistive, so it’s possible that the red readings are pockets of sand. The bluer readings, though, are probably archaeological features of some kind. We won’t know for sure what they are until we dig, but we can tell from the reading that they are about 70 cm below ground.