Archaeologists find traces of past activities in the ground. They study these traces, called artifacts, to learn about past people. Most archaeology involves digging. Winds and floods carry sand, dust, and soil alongside abandoned features and artifacts. Over time, these layers build up and bury them.
Before archaeologists dig, they usually do a surface survey. Level Ground Excavation walks straight lines across the area and records what they see.
Archaeological excavation methods vary depending on the type of site and geography. Some techniques focus on the vertical dimension of the site, while others are more horizontal and open up larger areas of a layer to reveal stratification. Each method has pros and cons, and no single method suits all types of sites.
The first step in archaeological excavation is to locate the site. This can be done using various techniques, such as remote sensing (including aerial photography), soil surveys, shovel tests, augured core samples, or trenches. Once the site has been located, it is necessary to record the location of all buried features and the context in which they are located. This information is important for interpreting the data collected during the excavation.
During the excavation, archaeologists work with teams of up to 15 people. Each team member has a specific job and responsibilities, including excavation, recording, and sieving. A supervisor leads the team and helps create and check detailed site records entered into a bespoke archaeological database on-site.
In addition to recording the artifacts found, the archaeological team also takes samples of deposits and soil from each context. These samples are then bagged and tagged with the grid number, square, and layer where they were found. These samples are then sent back to the lab for further analysis.
Archaeologists use various tools to excavate the site. Still, the most basic is the mason’s pointing trowel, a small brush that bricklayers and masons use to scrape away soil and identify features. The trowel is used to carefully and evenly scrape each layer of dirt, looking for changes in soil color or texture that may indicate a new level. The soil is then brushed into a bucket and sifted through the mesh to remove artifacts. The bagged artifacts are then recorded with a context description, and the excavation number is registered on a plan or section.
While many archaeological sites are excavated by choice, others are discovered by accident, such as when construction projects disturb ancient remains. These accidental discoveries are called “non-intrusive” or “non-destructive” excavations and can be quite valuable to archaeology. Artifacts found in these sites are often regarded as useful because they provide clues to the past lives of the ancient people.
Choosing the right location for an archaeological dig is a complex process. It requires a lot of planning and research. Businesses must consider factors such as market potential, cost of operations, transportation, and regulatory compliance. It’s also important to select a site accessible and convenient for workers. The selection process can be time-consuming, but ensuring a successful project is worth the effort.
Archaeologists use various techniques, including remote sensing and soil surveys, to find a good site. These techniques help them locate buried remains. They may also use shovel tests and augured core samples. Then, they can prepare a site map and take photographs of the area before starting excavation. This preparation is important because digging will destroy the original landscape, so it’s essential to have a clear record of how things looked before.
Before an archaeological dig begins, archaeologists must acquire permission from the landowner or government to excavate the site. They also have to write a research design that outlines the “who, what, where, when, and how” of fieldwork. A state historic preservation office must review the plan before a team can start digging. If the dig is on tribal lands, the research design must be approved by the tribes.
Once the site is selected, archaeologists decide which areas to investigate. Normally, they use trial trenches to test the potential for archaeological discoveries. These are small holes in the ground excavated and surveyed, similar to a construction trench. Alternatively, they may use watching briefs, which are cursory examinations of trenches that have been dug for something other than archaeology. These trenches are often associated with development-led excavations.
Archaeologists also make a detailed map of the excavation area. They then screen the soil and remove ground vegetation. They also create a datum point to mark the locations of artifacts and features discovered during excavation. These maps are invaluable for interpreting the results of an excavation.
Most archaeologists want to discover many items at a site, but they must do so in a way that doesn’t damage the ancient environment and culture where they are working. To achieve this, they must carefully choose the dig area and work in stages to avoid ruining valuable items.
Before excavation, archaeologists must conduct a surface survey of the area to determine its potential for sites. They do this by walking in straight lines back and forth across the entire area, looking for evidence of past human activity, such as walls or foundations, artifacts, and color changes in the soil that might indicate features. Any finds are recorded, and any areas of high concentration are noted. This information is then used to plan the excavation.
This information is sometimes combined with other techniques, such as geophysical surveys or aerial imaging, to locate sites. Once a site is identified, the archaeologist must obtain permission to excavate. Permission is usually given by the local state historic preservation office or, in the case of American work on tribal lands, by the appropriate government agency.
After the research design is approved, the archaeologist must obtain all the necessary permits and hire a crew. They may also need to consult with experts in the local area, including museum curators and historians. Often, these individuals have written about archaeological work that has taken place in the past and can help pinpoint the exact location of the site being investigated.
On the survey day, each team member walks straight, using a compass and long tape measure to ensure they cover the whole study area. They look for surface artifacts and other evidence of human activity, recording the findings on a record sheet. Any artifacts found are collected and bagged with a label that identifies the location where they were found on the ground.
As the fieldwork progresses, the results of the surface surveys are compared with the predictions made by analyzing the data from the magnetometry and other surveys. This helps the archaeologist to decide whether or not a dig is worth the cost of excavation.
If a decision is made to proceed with an excavation, the archaeologist must prepare a dig plan that details how each trench will be excavated. These plans are drawn up by a group of archaeological specialists called a ‘dig team’ and are submitted for approval to the local Historic Preservation Office. The plan includes information on the purpose of each trench, which cultural period it represents, and any other relevant factors that will be considered in the excavation process.
There are different ways to excavate sites, depending on the type of site, the area’s geology, time constraints, and what is being sought out. Some techniques favor the vertical dimension of a dig, digging deeper to reveal stratification. In contrast, others are more horizontal in their approach, opening up larger areas within a particular layer to get better spatial relationships between finds and features. Archaeologists usually use a mix of both, but no one method is universally applicable.
Before excavation begins, the archaeological site is surveyed and recorded. This can be done using GPS, tablet computers, digital cameras, and 3D laser scanners. The survey may include surface observation, walk-through surveys, shovel tests, and augured core sampling. This information is used to locate buried deposits and features.
Once the site has been located, it is divided into a grid to study each soil unit. This allows the archaeologists to see what layers of earth are present and which units contain artifacts that can be dated. Some squares on the grid are left untouched, allowing future scientists to study them with more advanced technology.
The actual digging process is often very laborious. The basic tool is the mason pointing trowel (the same tool that bricklayers, or masons, use). Trowels between three and five inches are most effective and are scraped carefully and evenly to expose any features underneath. Archaeologists are constantly looking for changes in soil color and texture that might indicate the beginning of a new level. The layer containing the artifacts is then dug out and recorded, along with its location in the grid and its provenience (a record of where it came from).
As layers are excavated, they can be grouped to form contexts, which are then interpreted. The aim is to understand the sequence of events that created the site, e.g., how a gardener swept soil into a corner and backfilled it over a bush or how a builder built a wall blown down by the wind. These contexts, called phases, can be grouped into larger groups by their relationships.