How does geophysics find buried remains?

It measures contrasts in soil properties, such as magnetism, electrical resistance, or radar reflections, that buried features like walls, ditches, and pits create relative to surrounding soil.

Which method is best?

It depends on the soils and the features sought; magnetometry suits many buried features and large areas, resistance suits stone structures, and radar gives depth information, so methods are often combined.

Geophysical Survey Methods

Geophysical survey detects buried archaeological features by measuring contrasts in the physical properties of the ground, mapping sites rapidly and without excavation.

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Definition

The application of near-surface geophysical techniques, such as magnetometry, resistivity, and ground-penetrating radar, to detect and map buried archaeological features non-invasively.

Scope

This topic covers the principal near-surface geophysical techniques used in archaeology: magnetometry, earth resistance, ground-penetrating radar, and electromagnetic methods. It addresses how each detects features through magnetic, electrical, or radar contrasts, the design and resolution of surveys, the processing and display of data as plots and slices, and the integration of geophysics with excavation.

Core questions

What physical contrasts allow buried features to be detected?
How do magnetometry, resistivity, and radar differ in what they sense?
How are geophysical data collected, processed, and displayed?
How are geophysical results integrated with excavation?

Key theories

Magnetic and resistance prospection: The detection of features through contrasts in soil magnetism, produced by burning and organic enrichment, and in electrical resistance, governed by moisture and compaction, which reveal ditches, walls, and pits.
Ground-penetrating radar: The use of reflected radar pulses to image subsurface interfaces and features in depth slices, allowing three-dimensional mapping of buried structures.

History

Archaeological geophysics began in the late 1940s and 1950s with the first resistivity and magnetic surveys, notably by Richard Atkinson and others. Magnetometry, resistance, and ground-penetrating radar matured through the later 20th century, and motorized multi-sensor arrays now allow rapid, high-resolution survey of large landscapes.

Debates

Interpreting anomalies without excavation: Geophysical anomalies can be ambiguous, so scholars debate how confidently features and their dates can be inferred from survey alone versus requiring ground-truthing by excavation.

Key figures

Anthony Clark
Chris Gaffney
Lawrence Conyers

Seminal works

gaffneygater2003
conyers2013
clark1996

Frequently asked questions

How does geophysics find buried remains?: It measures contrasts in soil properties, such as magnetism, electrical resistance, or radar reflections, that buried features like walls, ditches, and pits create relative to surrounding soil.
Which method is best?: It depends on the soils and the features sought; magnetometry suits many buried features and large areas, resistance suits stone structures, and radar gives depth information, so methods are often combined.