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Main article: Archaeological survey Monte Alban archaeological siteThe archaeological project then continues (or alternatively, begins) with a field survey. Regional survey is the attempt to systematically locate previously unknown sites in a region. Site survey is the attempt to systematically locate features of interest, such as houses and middens, within a site. Each of these two goals may be accomplished with largely the same methods. Survey was not widely practiced in the early days of archaeology. Cultural historians and prior researchers were usually content with discovering the locations of monumental sites from the local populace, and excavating only the plainly visible features there. Gordon Willey pioneered the technique of regional settlement pattern survey in 1949 in the Viru Valley of coastal Peru,[43][44] and survey of all levels became prominent with the rise of processual archaeology some years later.[45] Survey work has many benefits if performed as a preliminary exercise to, or even in place of, excavation. It requires relatively little time and expense, because it does not require processing large volumes of soil to search out artifacts. (Nevertheless, surveying a large region or site can be expensive, so archaeologists often employ sampling methods.)[46] As with other forms of non-destructive archaeology, survey avoids ethical issues (of particular concern to descendant peoples) associated with destroying a site through excavation. It is the only way to gather some forms of information, such as settlement patterns and settlement structure. Survey data are commonly assembled into maps, which may show surface features and/or artifact distribution. Inverted kite aerial photo of an excavation of a Roman building at Nesley near Tetbury in Gloucestershire.The simplest survey technique is surface survey. It involves combing an area, usually on foot but sometimes with the use of mechanized transport, to search for features or artifacts visible on the surface. Surface survey cannot detect sites or features that are completely buried under earth, or overgrown with vegetation. Surface survey may also include mini-excavation techniques such as augers, corers, and shovel test pits. If no materials are found, the area surveyed is deemed sterile. Aerial survey is conducted using cameras attached to airplanes, balloons, or even Kites.[47] A bird's-eye view is useful for quick mapping of large or complex sites. Aerial photographs are used to document the status of the archaeological dig. Aerial imaging can also detect many things not visible from the surface. Plants growing above a buried man made structure, such as a stone wall, will develop more slowly, while those above other types of features (such as middens) may develop more rapidly. Photographs of ripening grain, which changes colour rapidly at maturation, have revealed buried structures with great precision. Aerial photographs taken at different times of day will help show the outlines of structures by changes in shadows. Aerial survey also employs ultraviolet, infrared, ground-penetrating radar wavelengths, LiDAR and thermography.[48] Geophysical survey can be the most effective way to see beneath the ground. Magnetometers detect minute deviations in the Earth's magnetic field caused by iron artifacts, kilns, some types of stone structures, and even ditches and middens. Devices that measure the electrical resistivity of the soil are also widely used. Archaeological features whose electrical resistivity contrasts with that of surrounding soils can be detected and mapped. Some archaeological features (such as those composed of stone or brick) have higher resistivity than typical soils, while others (such as organic deposits or unfired clay) tend to have lower resistivity. Although some archaeologists consider the use of metal detectors to be tantamount to treasure hunting, others deem them an effective tool in archaeological surveying. Examples of formal archaeological use of metal detectors include musketball distribution analysis on English Civil War battlefields, metal distribution analysis prior to excavation of a 19th-century ship wreck, and service cable location during evaluation. Metal detectorists have also contributed to archaeology where they have made detailed records of their results and refrained from raising artifacts from their archaeological context. In the UK, metal detectorists have been solicited for involvement in the Portable Antiquities Scheme. Regional survey in underwater archaeology uses geophysical or remote sensing devices such as marine magnetometer, side-scan sonar, or sub-bottom sonar.[49] Excavation__Main article: Excavation (archaeology) Excavations at the 3800-year-old Edgewater Park Site, Iowa Archaeological excavation that discovered prehistoric caves in Vill (Innsbruck), Austria An archaeologist sifting for POW remains on Wake Island.Archaeological excavation existed even when the field was still the domain of amateurs, and it remains the source of the majority of data recovered in most field projects. It can reveal several types of information usually not accessible to survey, such as stratigraphy, three-dimensional structure, and verifiably primary context. Modern excavation techniques require that the precise locations of objects and features, known as their provenance or provenience, be recorded. This always involves determining their horizontal locations, and sometimes vertical position as well (also see Primary Laws of Archaeology). Likewise, their association, or relationship with nearby objects and features, needs to be recorded for later analysis. This allows the archaeologist to deduce which artifacts and features were likely used together and which may be from different phases of activity. For example, excavation of a site reveals its stratigraphy; if a site was occupied by a succession of distinct cultures, artifacts from more recent cultures will lie above those from more ancient cultures. Excavation is the most expensive phase of archaeological research, in relative terms. Also, as a destructive process, it carries ethical concerns. As a result, very few sites are excavated in their entirety. Again the percentage of a site excavated depends greatly on the country and "method statement" issued. In places 90% excavation is common. Sampling is even more important in excavation than in survey. It is common for large mechanical equipment, such as backhoes (JCBs), to be used in excavation, especially to remove the topsoil (overburden), though this method is increasingly used with great caution. Following this rather dramatic step, the exposed area is usually hand-cleaned with trowels or hoes to ensure that all features are apparent. The next task is to form a site plan and then use it to help decide the method of excavation. Features dug into the natural subsoil are normally excavated in portions to produce a visible archaeological section for recording. A feature, for example a pit or a ditch, consists of two parts: the cut and the fill. The cut describes the edge of the feature, where the feature meets the natural soil. It is the feature's boundary. The fill is what the feature is filled with, and will often appear quite distinct from the natural soil. The cut and fill are given consecutive numbers for recording purposes. Scaled plans and sections of individual features are all drawn on site, black and white and colour photographs of them are taken, and recording sheets are filled in describing the context of each. All this information serves as a permanent record of the now-destroyed archaeology and is used in describing and interpreting the site. Analysis__Main article: Post excavation Once artifacts and structures have been excavated, or collected from surface surveys, it is necessary to properly study them, to gain as much data as possible. This process is known as post-excavation analysis, and is usually the most time-consuming part of the archaeological investigation. It is not uncommon for the final excavation reports on major sites to take years to be published. At its most basic, the artifacts found are cleaned, cataloged and compared to published collections, to classify them typologically and to identify other sites with similar artifact assemblages. However, a much more comprehensive range of analytical techniques are available through archaeological science, meaning that artifacts can be dated and their compositions examined. The bones, plants and pollen collected from a site can all be analyzed (using the techniques of zooarchaeology, paleoethnobotany, and palynology), while any texts can usually be deciphered. These techniques frequently provide information that would not otherwise be known and therefore contribute greatly to the understanding of a site. Virtual archaeology__Some time around 1995 archaeologists started using computer graphics to build virtual 3D models of sites such as the throne room of an ancient Assyrian palace or ancient Rome.[50] This is done by collecting normal photographs and using computer graphics to build the virtual 3D model.[50] In more general terms, computers can be used to recreate the environment and conditions of the past, such as objects, buildings, landscapes and even ancient battles.[50] Computer simulation can be used to simulate the living conditions of an ancient community and to see how it would have reacted to various scenarios (such as how much food to grow, how many animals to slaughter, etc.)[50] Computer-built topographical models have been combined with astronomical calculations to verify whether or not certain structures (such as pillars) were aligned with astronomical events such as the sun's position at a solstice.[50] |
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