APAC    Geophysics

Geophysics
Geophysics (resistivity) is undertaken by measuring the relative resistance of an electrical current through the soil between mobile probes by comparison to the fixed value given by a set of control probes.
Newton Tump (click for larger image)

How this works is that soil that is undisturbed will have a background level of resistance to an electrical current. Soil that has been disturbed will have a different resistance which will vary dependent on the nature of its fill.

As an example: If a hole or ditch has been dug at some time in the past it is possible that the fill is looser and retains more moisture than the surrounding soil.

The higher moisture content would then have a lower resistance to an electrical current and would show up on the data as a low resistance feature.

Similarly, subsurface features such as stone walls are more resistant than the background fill and conversely would show up as high resistance.

When an area has been subjected to a resistivity survey the readings produced can undergo process in specialist programs to produce an area plot. Any anomalies to background resistance can then be recognised as patterns of varying resistance.

The experience of the archaeologist is utilised to interpret the patterns of resistance variation from which it is possible to identify the existence or even nature of the sub surface archaeology.

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