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Table I
The Benefits of Geophysics for Archaeology
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Archaeological Excavation
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Geophysical Surveying
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Inherently destructive
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Inherently nonintrusive and nondestructive
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Relatively expensive in cost per acre
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Relatively inexpensive in cost per acre
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Data often represent a few tiny windows into the subsurface
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Complete site coverage is feasible
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Characterization of large features or structures is difficult (the “Blind Men and the elephant” problem)
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Large features can be completely mapped
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Complete data collection on multi-layer or multi-component sites can take years
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Complete data collection on multi-layer or multi-component sites can be done in hours to days
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Horizons or features typically recognizable only by color and/or texture
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Horizons or features can be recognized by very subtle differences in texture, moisture content, mineralogy, compaction, magnetization, magnetic susceptibility, electrical conductivity, dielectric properties, or density
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Reconnaissance or prospecting is often a “needle in a haystack” proposition
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Complete site coverage produces rapid, high confidence propsecting
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Difficult to impossible on many flooded sites
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Geophysics is equally effective for underwater and underground targets
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Artifacts and features can be positively identified
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Artifacts and features cannot generally be identified based on geophysics alone
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Minute artifacts can be detected and recovered
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The deeper an artifact or feature, the larger it must be to be detectable
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Back to Archaeological Geophysics
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Table II
Geophysical Techniques for Archaeology
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Method
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Sensitive To...
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Typical Targets
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Typical Application
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Typical Environment
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Magnetic Mapping
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Iron or iron-bearing materials, oxidized soils, fired materials, compacted soils
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Hearths or fire pits, burned structures, iron artifacts, oxidized soils
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Prospecting
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Land or water
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Electromagnetic Mapping
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Metals, moisture content variations, clay vs. sand soils, organic material, stones in soil
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Foundation remnants, wellshafts or privies, artifact caches
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Prospecting
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Land
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Resistivity Methods
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Metals, moisture content variations, clay vs. sand soils, organic material, stones in soil
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Foundation remnants, wellshafts or privies, artifact caches, tunnels or shafts, soil horizon thicknesses
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Prospecting or Imaging
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Land or water
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Seismic Methods
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Large stones, compacted soils, cavities, organic lenses
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Foundation remnants, floors, tunnels or shafts, soil horizon thicknesses
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Imaging
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Land or water
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Microgravity
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Stone, compacted soils, cavities, large organic lenses
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Tunnels, shafts, vaults, buried rock structures
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Prospecting
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Land
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Ground Penetrating Radar
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Differences in nearly any physical property
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Nearly anything underground with sufficient size relative to depth
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Prospecting or Imaging
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Land
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Sonar
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Differences in density or surface roughness
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Nearly anything underwater
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Prospecting or Imaging
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Water
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Back to Archaeological Geophysics
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