Geophysical Technique

Resistance

A resistance survey measures the subsurface variation in soil resistance by passing a current into the ground through two electrodes and measuring the voltage between a second pair of electrodes on the ground surface. The resistance of the earth is dependent upon properties that include the soil compaction, saturation, mineral content, and porosity of rocks and other materials. Resistance surveys can map features where a distinct change in these properties occurs, including pits, trenches, foundations, compacted or disturbed surfaces, and changes in soil type. For example a humic filled pit excavated into a background of well-drained sandy gravels, covered by topsoil provides an example of a feature of relatively good conductivity (low resistance) within a background of poor conductivity (high resistance). The current flow concentrates through the pit fill in preference to the higher resistance of the sandy gravels due to the compaction, saturation level, and mineral content of the fill material. A corresponding disturbance in and around the area of the pit can be measured at the ground surface.

See What Meg Sees: Instructions for Interpreting the Data

Using the tool below, click on individual grids for a closer look at the Resistivity data Meg and her team gathered at the Dillard site. You can toggle between an arieal view of the landsape, the map of the data only, and then read Meg's interpertation of each of the data points as you learn more about what each grid reveals.  Each grid you click on will become highlighted.

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MEET THE TEAM

Dr. Meg Watters

Dr. Meg Watters

Remote Sensing & Visualization Specialist

Bryan Haley

Bryan Haley

Archaeological Geophysist

Dr. Duncan McKinnon

Dr. Duncan McKinnon

Geophysics Specialist

The resistance survey mapped a number of pit house like structures.  What it mapped specifically was the higher resistance of the structure material in contrast to the lower resistance of the surrounding site soils.  Magnetometry survey of this area identified the same and additional pit house like structures.  Magnetometry survey also identified a series of pits, not mapped in the resistance survey, that are thought to represent a fence that would have enclosed the cluster of pit house like structures just north of the Great Kiva. 

INTERPRET MORE DATA

Ground-penetrating Radar

Ground-penetrating Radar

GPR maps features such as walls, trenches, pits, and more.

Magnetometry

Magnetometry

Magnetic survey measures the variation of magnetic fields of the earth.

Magnetic Susceptibility

Magnetic Susceptibility

This survey induces an electromagnetic field into the earth through a transmitting coil.