Geophysical prospecting

Geophysical prospecting

Geophysical prospecting is the use of high-resolution geophysical methods to discover archeological sites. It is common for this procedure to also be called “remote sensing” or “archeogeophysics”. There are great advantages to using geophysical methods because they are nondestructive and provide rapid reconnaissance.

Their major limitation is that they use non-contact techniques. The best they can do is detecting anomalies, which archeologists must then investigate directly to interpret. These methods are also instrument-intensive and initially very costly. Metal detectors do have legitimate archeological uses.

Metal detectors are electromagnetic devices that work at low frequencies. They are effective to the depth that is approximately the width of the search coil. Depth also depends on the size and orientation of the buried object and the amount of corrosion. Geophysical techniques have been used in mineral prospecting for several hundred years, beginning with the use of magnetic compasses in exploring for iron ore. Resistivity measurements followed in the search for base metals.

The use of applied geophysics for mineral and hydrocarbon exploration as we know it today, likely began in the 1950’s, with the advent of sensitive magnetometers, gravity meters, battery-powered electronic equipment, and the application of information theory and computer processing to seismic data acquisition.

Geophysical techniques are routinely used in an exploration program to help the project geologist find areas that are favorable for the type of target being pursued. They can be used to directly detect some minerals, indirectly detect others, and to map geological and structural features in exploration programs.

Other uses of metal detectors include the detection of land mines, the detection of weapons such as knives and guns, especially at airports, malls, geophysical prospecting, archaeology and treasure hunting. Metal detectors are also used to detect foreign bodies in food, and in the construction industry to detect steel reinforcing bars in concrete and pipes and wires buried in walls and floors.