Review paper: Determination of the earth's resistivity by surface measurements

Analyzing a layered earth, regarding its resistivity distribution down to several hundred meters depth is no problem. This fact, often not well known in neighbor disciplines, is demonstrated, outlining the possibilities and limitations of the methods available. After a short introduction into the principle of geoelectrical sounding, practical results are shown by case histories from some selected parts of the world. The main conclusion is that low resistivities ( 50 ohm.m) predominate at the surface even in arid areas and deserts. The reason for this surprising fact is the clay and saline component within the top layers.