Archaeological Sites

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Archaeological Sites

Archaeological sites are those areas that provide information and materials concerning the distant past of humans. Archaeologists are concerned with the activities of people and nature, which have created evidence of a cultural past. Such evidence, which may include any remnant of human habitation, is referred to as the archaeological record. The processes that produce this evidence are called formation processes.

There are two types of formation processes: cultural and environmental. Cultural formation processes are those that follow the actual use of an artifact. Environmental formation processes are those agents that impact cultural materials at any stage of their existence.

Cultural formation

The four cultural formation processes are reuse, cultural deposition, reclamation or archaeological recovery, and disturbance. Reuse might include recycling, secondary use, or use by another party. Cultural deposition processes take cultural materials from the context in which they are used in a culture and place them in an environmental context; examples include discarded dishes, burials, and abandonments. Reclamation processes are those in which archaeological materials are retrieved for reuse by a culture; examples include scavenging, looting of previously deposited artifacts, and archaeological recovery. Disturbance processes alter Earth’s surface and alter archaeological materials, deposits and sites; examples include plowing and land leveling.

Environmental formation

Environmental formation processes include the chemical, physical, and biological processes by which nature alters cultural materials. The scale at which these processes affect cultural material may be at the artifact level (e.g., the rotting of wood or the corrosion of metals), the site level (e.g., the burrowing of animals), or the regional level (the burial or erosion of sites).

Archaeologists must sort out the contributions of the various formation processes to achieve new understandings of past human behavior. An artifact such as a hand axe would be expected to acquire signs of wear in the course of normal use, but could also acquire similar patterns of wear from cultural and environmental processes. By identifying ways that formation processes have altered an artifact, the archaeologist can better assess the way the artifact was used in the culture that produced it.

Finding an archaeological site

Besides drawing on information from large archaeological sites such as Stonehenge (England) and Angkor Wat (Cambodia), archaeologists must also rely on data from a myriad of much smaller sites if they are to construct an accurate interpretation of the economic, environmental, and ideological factors that governed occupation of the larger sites. In many cases, the only evidence of human occupation must come from the remnants of seasonal campsites and artifacts such as stone tools or bones.

In order to efficiently sample sites within a region and locate very small sites, archaeologists have developed a variety of ground-survey and remote-sensing techniques.

Remote sensing and geophysical analysis

Although some archaeological sites can be recognized above ground, the majority lie beneath the ground’s surface. Remote sensing techniques allow archaeologists to identify buried sites. In addition, by examining the ways in which human intervention has altered the surface near a site (e.g., through the construction of refuse pits or hearths), the archaeologist may be able to identify patterns of previous usage.

Archaeologists may employ techniques borrowed from the fields of geophysics and geochemistry to detect and map archaeological sites and features. Many geophysical techniques, including electrical resistance measurements of the soil above a site and magnetic measurements of a pottery kiln, were first employed by archaeologists in the 1940s and 1950s.

Satellite detectors have also been used to monitor the reflected solar radiation above a site. The characteristics of the reflected light allow the archaeologist to identify differences in soil or vegetation covering a site, and, at sufficiently high resolutions, to recognize archaeological features. In this way, archaeologists have been able to map out drainage canals once used by Mayan farmers, which are now lying beneath the umbrella of the Yucatan rainforest.

Airborne thermal detectors, capable of monitoring the surface temperature of the soil and covering vegetation, take advantage of differences in the way materials retain heat to isolate archaeological features from surrounding soil. With this technique, buried Egyptian villages appear to glow at night beneath thin layers of sand.

Electrical resistivity measurements of the soil are sensitive to the presence of water and dissolved salts in the water. Because constriction materials such as granite or limestone have a higher electrical resistance than the surrounding soil, electrical resistivity measurements may be of use in determining the locations of buried structures such as stone walls.

The magnetic properties of soil depend on the presence of iron particles, which when heated to sufficiently high temperatures tend to align themselves with the Earth’s magnetic field. However, Earth’s magnetic field and intensity change over time. Wherever human activity alters the iron compounds in the soil by subjecting them to high temperatures, for example by building fires in a hearth or firing pottery in a kiln, upon cooling the heated soil takes on magnetic properties that reflect the direction and intensity of Earth’s magnetic field at the time of cooling. Since archaeologically related changes in local magnetic fields may only amount to one part in 10, 000, and because of daily fluctuations in the magnetic field due to electrical currents in the ionosphere, this technique usually requires monitoring of Earth’s field at a reference point during the archaeological investigation.

Other electromagnetic measurements used to probe a site may examine the soil for phosphates and heavy minerals often associated with past human habitation.

Three dimensional representations of a buried feature may be constructed using ground-sensing radar or resistivity profiling to obtain vertical geophysical cross-sections across a site. When placed beside each other, these sections create a three-dimensional image of buried objects.

Ground surveys

The techniques of ground surveying date to the 1930s and 1940s. Ground surveys require no special equipment, just an observant archaeologist with some knowledge of what might be found at a site. Ground survey records may include notes about any visible cultural features and artifacts on the site, site measurements, preparing maps or sketches of the site, and sometimes gathering small collections of artifacts. Surface artifacts may be gathered either as random grabs or complete samplings in a given area.

Site assessments

Initially, the archaeologist must determine the size, depth, and stratification of a site. Second, the age or ages of the site must be determined. Third, the types of artifacts and features present at the site must be identified. Finally, information about the environment and the way that it influenced human habitation at the site must be known.

Site assessment techniques fall into two categories: destructive and nondestructive. Surface collecting, testing with shovels, digging pits, and mechanical trenching all disturb the site, and are considered destructive. Nondestructive techniques include mapping and remote sensing.

KEY TERMS

Artifact— An artificially-made object that has been shaped and fashioned for human use.

Electrical resistivity— A measure of the resistance (opposition) an object poses to electrical current flowing through it.

Magnetic field— The electromagnetic phenomenon producing a magnetic force around a magnet.

Radar— A method of detecting distant objects based on the reflection of radio waves from their surfaces.

Solar radiation— Energy from the sun.

Stratification— A method of describing the ages of different strata of rocks or soil, based on the assumption that the oldest material will usually be found at the bottom layer.

Thermal detector— A device that detects heat.

Resources

BOOKS

Fagan, Brian M. Archaeology: A Brief Introduction. Upper Saddle River, NJ: Pearson Prentice Hall, 2006.

Haviland, William A. Evolution and Prehistory: The Human Challenge. Belmont, CA: Wadsworth/Thomson Learning, 2005.

Palmer, Douglas. Unearthing the Past: The Great Archaeological Discoveries that have Changed History. Guilford, CT: Lyons Press, 2005.

Russell, Ian, editor. Images, Representations, and Heritage: Moving Beyond Modern Approaches to Archaeology. New York: Springer, 2006.

Sullivan, George. Discover Archeology: An Introduction to the Tools and Techniques of Archeological Fieldwork. Garden City, NY: Doubleday & Company, 1980. Thomas, David Hurst. Archaeology. Belmont, CA: Thomson/Wadsworth, 2006.

Waters, Michael R. Principles of Geoarchaeology: A North American Perspective Tucson, AZ: University of Arizona Press, 1997.