Archaeology is the study of the past by looking for the remains and artifacts (historical things) left by the people who lived long ago. These remains can include old coins, tools, buildings, and inscriptions. Archaeologists, the people who study archaeology, use these remains to understand how people lived.
Archaeologists think it is important to understand the past, because so many people use the past to know where they come from.
Fields of interest
Archaeologists do not all study the same civilizations, they specialize in different areas of interest. Some fields of interest include Ancient Egypt (these specialists are called Egyptologists), Ancient China, or the Vikings. Archaeologists study every civilization that is known, especially the ones where there is no written history. They can study any time period. For example, one might study the beginning of human life in Africa, or study World War II. Marine archaeologists study things that are now underwater. They search for sunken ships or cities that have been lost under the sea.
Stonehenge, in England, is a famous archaeological site, or place. Other famous sites include the Roman Forum, Angkor Wat, Machu Picchu, and Great Zimbabwe. In many countries, governments and other groups of people protect important sites so that they will not be destroyed and so that visitors can always come and see them.
Sometimes archaeological sites are found when foundations are dug for new buildings. Archaeologists have to work quickly when this happens, because people who are building often don't have a lot of time. Many times as soon as the archaeologists are done with their work, the remains that they have found will be covered over, unless they are very important.
An archaeological investigation usually involves several distinct phases, each of which employs its own variety of methods. Before any practical work can begin, however, a clear objective as to what the archaeologists are looking to achieve must be agreed upon. This done, a site is surveyed to find out as much as possible about it and the surrounding area. Second, an excavation may take place to uncover any archaeological features buried under the ground. And, third, the data collected from the excavation is studied and evaluated in an attempt to achieve the original research objectives of the archaeologists. It is then considered good practice for the information to be published so that it is available to other archaeologists and historians, although this is sometimes neglected.
Before actually starting to dig in a location, remote sensing can be used to look where sites are located within a large area or provide more information about sites or regions. There are two types of remote sensing instruments—passive and active. Passive instruments detect natural energy that is reflected or emitted from the observed scene. Passive instruments sense only radiation emitted by the object being viewed or reflected by the object from a source other than the instrument. Active instruments emit energy and record what is reflected. Satellite imagery is an example of passive remote sensing. Here are two active remote sensing instruments:
Lidar (Light Detection and Ranging) A lidar uses a laser (light amplification by stimulated emission of radiation) to transmit a light pulse and a receiver with sensitive detectors to measure the backscattered or reflected light. Distance to the object is determined by recording the time between the transmitted and backscattered pulses and using the speed of light to calculate the distance travelled. Lidars can determine atmospheric profiles of aerosols, clouds, and other constituents of the atmosphere.
Laser Altimeter A laser altimeter uses a lidar (see above) to measure the height of the instrument platform above the surface. By independently knowing the height of the platform with respect to the mean Earth's surface, the topography of the underlying surface can be determined.
The 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, and survey of all levels became prominent with the rise of processual archaeology some years later.
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.) 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.
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, UAVs, or even Kites. 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.
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.
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. Sampling is even more important in excavation than in survey.Sometimes large mechanical equipment, such as backhoes (JCBs), is 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.
Once artifacts and structures have been excavated, or collected from surface surveys, it is necessary to properly study them. This process is known as post-excavation analysis, and is usually the most time-consuming part of an archaeological investigation. It is not uncommon for final excavation reports for major sites to take years to be published.
At a basic level of analysis, artifacts found are cleaned, catalogued and compared to published collections. This comparison process often involves classifying them typologically and identifying 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. Bones, plants, and pollen collected from a site can all be analyzed using the methods 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 they contribute greatly to the understanding of a site.
Computational and virtual archaeology
Computer graphics are now used to build virtual 3D models of sites, such as the throne room of an Assyrian palace or ancient Rome. Photogrammetry is also used as an analytical tool, and digital 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. Agent-based modeling and simulation can be used to better understand past social dynamics and outcomes. Data mining can be applied to large bodies of archaeological 'grey literature'.
Archaeologists around the world use drones to speed up survey work and protect sites from squatters, builders and miners. In Peru, small drones helped researchers produce three-dimensional models of Peruvian sites instead of the usual flat maps – and in days and weeks instead of months and years.
Drones costing as little as £650 have proven useful. In 2013, drones have flown over at least six Peruvian archaeological sites, including the colonial Andean town Machu Llacta 4,000 metres (13,000 ft) above sea level. The drones continue to have altitude problems in the Andes, leading to plans to make a drone blimp, employing open source software.
Jeffrey Quilter, an archaeologist with Harvard University said, "You can go up three metres and photograph a room, 300 metres and photograph a site, or you can go up 3,000 metres and photograph the entire valley."
In September 2014 drones weighing about 5 kg (11 lb) were used for 3D mapping of the above-ground ruins of the Greek city of Aphrodisias. The data is being analysed by the Austrian Archaeological Institute in Vienna.
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