Yes archaeology often does involve excavation, but more happens out in the field than just breaking ground! There are many non-invasive techniques that can be used to supplement or even replace excavation.
Two Crow Canyon field school participants using an RM15 electrical resistance meter. (1)
Combining Field Methods
When non-invasive techniques are used to assist excavation, it can make for a faster, more focused, and less intrusive process as a whole since specific targeted areas can be identified first via non-invasive methods. This combining of techniques can help combat the culture of “shovel bumming” where field techs are overworked and often injured. It is also a more respectful approach to archaeology as sites often carry great significance, meaning and/or sacredness for many living peoples who have a stake in its protection and preservation.
Below, we will review five non-invasive techniques implemented within archaeology - their benefits and drawbacks as well as their ideal applications to enrich archaeological findings.
Field Surveying
Field surveys are the easiest and most cost effective to conduct, however, they are time consuming. It entails a group of archaeologists or participants lining up walking across an open area where the ground is easily visible in a methodical manner, recording and/or gathering any visible features or artifacts.
Pros:
most cost effective
doesn't require electronic equipment or experts
beneficial to commercial and rescue excavations
Cons:
can be very time-consuming especially for large sites
requires open, ideally plowed, fields
often only a small percentage of sites are covered during field surveys which does not include the surrounding landscape
Application:
Field walking can be effective in gaining a rough understanding of the type and function of a site. It can be used to expand an excavation and understand a site within its natural context. Field walking is often used as a tool for location sites where environments allow.
Aerial photography
Aerial photography can help identify sites not visible from ground level via discolorations of soils or crops. This is usually conducted via satellite imaging or the use of drones.
Pros:
less demanding than geophysical surveys and LiDAR and more efficient than field walking
allows the site to viewed in its entirety and within its natural context
the type of site or features of a specific period or style can be identified
Cons:
requires extensive planning and favorable conditions
equipment and materials must be used and analyzed by experts
Application:
Aerial photography is most helpful for the initial planning process of excavation and research where mapping, site identification, and locating are all needed.
Geophysical and Geochemical Surveys
Geophysical surveys are easy to conduct and requires little expertise. There are a variety of geophysical surveys such as ground penetrating radar (GPR), magnetic surveying, and resistivity. Geochemical surveys involve sampling soils, waters, bedrock, and other mineral deposits in order to analyze the chemical and elemental concentrations.
Pros:
can estimate the depth of deposits
easy execution with training and relatively little equipment
immediate results and data collection
Cons:
terrain needs to be relatively flat
results can be affect by environmental factors such as moisture or soil discrepancies
does not identify the details or composition of the flagged soil disturbances
Application:
Geophysical and geochemical surveys can provide additional understanding of a site's features or a more holistic understanding of a site's phases if only a small percentage was excavated. They can be implemented at all stages: before during, and after excavation. Geophysical and geochemical surveys can also check the accuracy of aerial photography crop mark sites.
LiDAR
LiDAR can create an accurate and detailed model of the landscape. LiDAR emits a laser in all directions and records the time it takes for the light to return to the sensor in order to calculate its distance.
Pros:
fast and accurate results
can create 3D models of the site and surrounding environment
can recognize and record sites that are obstructed by canopies or thick foliage
Cons:
requires technical experience and training to interpret the data
can be very expensive to rent or buy equipment
Application:
LiDAR can allow for a more detailed and accurate model of the site than aerial photography. LiDAR is usually the initial planning of an archaeological project and can, in some instances, be sufficient in place of excavation.
GIS
GIS or Geographic Information System takes data from geographical surveys, historical maps and accounts, and photographic records to reconstruct a virtual picture of the past.
Pros:
can highlight patterns, relationships, and trends otherwise not seen from one single method of data collection
can accurately predict the location of sites
Cons:
dependent upon maps and recorded data which only a handful of sites have
inaccurate maps or missing data and can result inaccuracies or conflicting analyses
requires significant updating of databases which is not always possible in archaeological setting where excavations, data analyses, and classification are fluctuating throughout the project
Applications:
GIS can be useful in predicting the location of sites and assist the the excavation planning. It can also be useful post-excavation to combine different databases and classifications to highlight trends or patterns within and across sites.
Which should be used?
No one method is better than the others. To determine which methods should be used to replace or supplement excavation, one must consider the time constraints, budget, site climate, community needs, and research questions and goals. Often it is a unique combination of several methods that creates the most holistic and efficient analysis of a site that one method alone could not do.
Referenced Works:
(1) Crow Canyon College Field School. (2015). Electrical Resistivity Survey. [Image]. Crow Canyon Archaeological Center 2015 College Field School. https://crowcanyon2015collegefieldschool.wordpress.com/2015/06/17/wednesday-june-17th-electrical-resistivity-survey/
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