10.1 Excavation methods

Excavation methods are the backbone of archaeological fieldwork. They allow researchers to uncover and study physical remains of past human activities. From horizontal and vertical approaches to single context recording, these techniques help piece together the puzzle of our shared history.

The tools and documentation processes used in excavations are crucial for preserving information about sites and artifacts. From trowels and brushes to remote sensing equipment, archaeologists employ a range of tools to carefully uncover and record their findings, ensuring that valuable data is not lost.

Types of excavation methods

• Excavation methods are crucial in archaeology to uncover and study the remains of past human activities
• The choice of excavation method depends on factors such as the site's characteristics, research questions, and available resources
• Different excavation methods provide varying levels of detail and are suited for specific contexts

Horizontal vs vertical excavation

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• Horizontal excavation focuses on exposing and studying a site's spatial layout by removing layers of soil evenly across a wide area
• Vertical excavation involves digging deeper into the ground to examine the stratigraphy and chronology of a site
• Horizontal excavation is useful for understanding the relationships between features and artifacts within a single time period (Pompeii)
• Vertical excavation helps establish the sequence of events and changes over time at a site (Tell sites in Mesopotamia)

Arbitrary vs natural levels

• Arbitrary levels are predetermined, fixed depths (10 cm) used to excavate a site, regardless of the natural stratigraphy
• Natural levels follow the actual layers of soil or cultural deposits, which may vary in thickness and composition
• Arbitrary levels are useful when the stratigraphy is unclear or when consistent measurements are needed for comparative analysis
• Natural levels provide a more accurate representation of the site's formation processes and cultural activities (Ash layers from volcanic eruptions)

Single context recording

• Single context recording is a method that treats each depositional event or action as a discrete unit to be excavated and recorded separately
• This method allows for a highly detailed understanding of the site's stratigraphy and the relationships between different contexts
• Each context is given a unique number and is fully documented through written descriptions, drawings, and photographs
• Single context recording is particularly useful in complex urban sites with multiple phases of occupation (Medieval towns)

Tools used in excavation

• Archaeologists employ a variety of tools to carefully uncover, record, and interpret the remains of past human activities
• The choice of tools depends on the nature of the site, the materials being excavated, and the desired level of precision
• Advancements in technology have introduced new tools that enhance the efficiency and accuracy of excavations

Hand tools

• Hand tools are the most basic and commonly used implements in archaeological excavations
• Trowels, brushes, and dental picks are used for delicate work, such as exposing fragile artifacts or cleaning surfaces
• Shovels, pickaxes, and mattocks are used for removing larger amounts of soil or breaking through hard layers
• Hand tools allow for a high degree of control and precision in excavation (Uncovering a delicate mosaic floor)

Mechanical tools

• Mechanical tools, such as backhoes and bulldozers, are used for large-scale excavations or for removing overburden
• These tools can quickly remove large volumes of soil, exposing deeper layers or features
• Mechanical tools are often used in conjunction with hand tools for more detailed work
• The use of mechanical tools requires careful planning and supervision to avoid damaging archaeological remains (Removing topsoil at a large settlement site)

Remote sensing equipment

• Remote sensing equipment allows archaeologists to gather data about a site without physically disturbing it
• Ground-penetrating radar (GPR) uses electromagnetic waves to create images of subsurface features and layers
• Magnetometers detect variations in the earth's magnetic field, which can indicate the presence of buried features (Hearths or kilns)
• LiDAR (Light Detection and Ranging) uses laser pulses to create detailed 3D maps of a site's surface and topography

Documenting the excavation process

• Thorough documentation is essential in archaeology to preserve information about a site and its context
• Documentation allows for the interpretation, analysis, and sharing of data long after the excavation has been completed
• Various methods are used to capture different aspects of the excavation process and the archaeological remains

Field notes and journals

• Field notes and journals are written records of observations, measurements, and interpretations made during the excavation
• They include descriptions of soil layers, features, artifacts, and any changes or decisions made during the excavation process
• Field notes should be detailed, clear, and organized to facilitate later analysis and interpretation
• Standardized forms and terminology are often used to ensure consistency and comparability between different excavations

Photographs and videos

• Photographs and videos provide visual documentation of the excavation process and the archaeological remains
• They capture the appearance, condition, and context of features and artifacts before they are removed or altered
• Photographs are taken at various stages of the excavation, from the initial site survey to the final recording of contexts
• Videos can be used to document the excavation process, provide virtual tours of the site, or record interviews with team members

Drawings and maps

• Drawings and maps are graphic representations of the site's layout, stratigraphy, and features
• Plan drawings show the horizontal relationships between features and artifacts at a specific depth or context
• Section drawings depict the vertical relationships between layers and features, revealing the site's stratigraphy
• Maps provide an overview of the site's location, topography, and surrounding landscape
• Drawings and maps are created using standardized scales, symbols, and conventions to ensure accuracy and clarity

Stratigraphy and context

• Stratigraphy is the study of the layering of sediments and cultural deposits over time
• Context refers to the physical and temporal relationships between archaeological remains within these layers
• Understanding stratigraphy and context is crucial for interpreting the sequence of events and activities at a site

Law of superposition

• The law of superposition states that, in a sequence of undisturbed layers, the oldest layers are at the bottom and the youngest layers are at the top
• This principle allows archaeologists to establish a relative chronology of the site based on the order of the layers
• The law of superposition can be complicated by natural or cultural disturbances, such as erosion, animal burrows, or later human activities

Harris matrix

• The Harris matrix is a diagrammatic representation of the stratigraphic relationships between different contexts at a site
• It uses lines and boxes to show which contexts are earlier, later, or contemporaneous with each other
• The Harris matrix helps archaeologists visualize the sequence of events and phases of occupation at a site
• It is particularly useful in complex urban sites with multiple layers of occupation and intersecting features (Medieval towns)

Interpreting stratigraphic relationships

• Interpreting stratigraphic relationships involves analyzing the physical characteristics and contents of each layer or context
• The nature of the soil, the presence of artifacts or ecofacts, and the boundaries between layers provide clues about the formation processes and human activities at the site
• Stratigraphic relationships can reveal information about the duration and intensity of occupation, the function of different areas within the site, and changes in the use of space over time
• Interpreting stratigraphy requires careful observation, recording, and comparison of contexts across the site (Identifying different phases of a building's construction and use)

Sampling strategies

• Sampling strategies are used to select a representative portion of a site for excavation and analysis
• Sampling allows archaeologists to gather data efficiently and effectively, especially when dealing with large or complex sites
• Different sampling strategies are employed depending on the research questions, site characteristics, and available resources

Judgmental sampling

• Judgmental sampling involves selecting areas for excavation based on the archaeologist's knowledge, experience, and intuition
• This strategy focuses on areas that are likely to yield the most informative or significant data, such as visible features or artifact concentrations
• Judgmental sampling is useful for targeted investigations or when time and resources are limited
• However, it may introduce bias and limit the representativeness of the sample (Excavating a specific building or activity area within a larger site)

Systematic sampling

• Systematic sampling involves selecting areas for excavation based on a predetermined grid or pattern
• This strategy ensures that the sample is evenly distributed across the site and reduces the potential for bias
• Systematic sampling can be random (selecting units at random within the grid) or stratified (selecting units based on specific criteria, such as soil type or topography)
• This approach is useful for obtaining a representative sample of the site and for making statistical inferences about the population (Sampling a large agricultural field to estimate crop yields)

Flotation and sieving

• Flotation and sieving are techniques used to recover small artifacts, ecofacts, and biological remains from excavated sediments
• Flotation involves immersing sediments in water, allowing light materials (seeds, charcoal) to float to the surface and be collected
• Sieving involves passing sediments through a series of screens with progressively smaller mesh sizes to separate artifacts and ecofacts by size
• These techniques are essential for recovering data about past environments, diets, and economic activities (Recovering charred plant remains from a hearth)

Conservation during excavation

• Conservation during excavation involves the protection and stabilization of archaeological remains as they are exposed and removed from their original context
• Conservation measures are crucial to ensure that artifacts and features are preserved for future study and display
• Different materials and contexts require specific conservation techniques and expertise

Protecting fragile artifacts

• Fragile artifacts, such as textiles, leather, or metal objects, require special care during excavation and removal
• Techniques such as block lifting (removing the artifact with its surrounding soil) or consolidation (applying a stabilizing agent) may be used
• Fragile artifacts are often excavated by conservators or under their guidance to minimize damage
• Once removed, fragile artifacts are stored in controlled environments and undergo further conservation treatments (Excavating a delicate glass vessel)

Stabilizing structures

• Archaeological structures, such as walls, floors, or hearths, may be unstable or vulnerable to collapse when exposed during excavation
• Stabilization measures, such as temporary supports, braces, or protective covers, are used to prevent damage and ensure the safety of the excavation team
• In some cases, structures may be partially or fully reconstructed using original materials or modern equivalents to aid in interpretation and presentation (Stabilizing a mudbrick wall)

Environmental controls

• Environmental controls are used to regulate the temperature, humidity, and light levels during excavation and storage of archaeological remains
• These controls help prevent deterioration, such as metal corrosion, organic decay, or salt crystallization
• Techniques include shading exposed features, using moisture barriers, or creating microclimate storage containers
• Environmental monitoring devices, such as thermohygrometers or data loggers, are used to track and adjust conditions as needed (Maintaining stable humidity levels in a tomb)

Post-excavation analysis

• Post-excavation analysis involves the study and interpretation of archaeological remains after they have been removed from the site
• This process includes cleaning, cataloging, and examining artifacts and ecofacts to extract information about the past
• Post-excavation analysis is a collaborative effort involving various specialists and techniques

Cleaning and cataloging finds

• Artifacts and ecofacts are carefully cleaned to remove dirt, corrosion, or other accretions that may obscure their features or hinder analysis
• Cleaning methods vary depending on the material and condition of the finds, and may include dry brushing, wet cleaning, or chemical treatments
• Once cleaned, finds are cataloged using a standardized system that records their provenience (location within the site), physical characteristics, and any initial interpretations
• Cataloging allows for the efficient storage, retrieval, and comparison of finds across the site and with other collections (Cleaning and cataloging a ceramic assemblage)

Specialist analyses

• Specialist analyses involve the examination of specific materials or aspects of the archaeological record by experts in various fields
• Examples include:
  • Zooarchaeology: the study of animal remains to reconstruct past environments, diets, and human-animal relationships
  • Paleoethnobotany: the study of plant remains to understand past landscapes, agriculture, and plant use
  • Archaeometallurgy: the study of metal artifacts to investigate production techniques, trade, and social organization
• Specialist analyses often employ scientific techniques, such as microscopy, chemical analysis, or DNA sequencing, to extract detailed information from the remains (Conducting stable isotope analysis on human teeth to reconstruct migration patterns)

Interpreting the site

• Interpreting the site involves synthesizing the data from the excavation, documentation, and specialist analyses to create a comprehensive understanding of the past activities and processes at the location
• Interpretation considers the spatial and temporal relationships between features, artifacts, and ecofacts, as well as their broader cultural and environmental contexts
• Multiple lines of evidence are used to support or refute hypotheses about the site's chronology, function, and significance
• Interpretation is an ongoing process that may be revised as new data or theoretical perspectives emerge (Reconstructing the daily life in a Roman villa based on the architectural layout, artifact assemblages, and environmental remains)

Challenges in excavation

• Archaeological excavations often face various challenges that can impact the recovery, interpretation, and preservation of the remains
• These challenges may be practical, financial, or ethical in nature and require careful consideration and mitigation strategies

Site disturbance and looting

• Archaeological sites may be disturbed or damaged by natural processes, such as erosion, animal activity, or plant growth, which can displace or destroy archaeological remains
• Human activities, such as construction, agriculture, or looting, can also severely impact the integrity and preservation of sites
• Looting, or the illegal removal of artifacts for profit or personal collection, is a major problem that can result in the loss of valuable information and context
• Strategies to combat looting include site monitoring, community engagement, and legal protection (Documenting the extent of looting at a Maya temple)

Time and budget constraints

• Archaeological excavations are often limited by the available time and financial resources
• Excavation seasons may be short due to weather conditions, permit restrictions, or academic schedules, putting pressure on the team to work efficiently
• Budgets for excavation, analysis, and conservation can be tight, requiring careful planning and prioritization of resources
• Time and budget constraints may necessitate the use of sampling strategies or the phasing of excavation and analysis over multiple seasons (Conducting a rescue excavation ahead of a construction project)

Ethical considerations

• Archaeological excavations raise various ethical considerations regarding the treatment of human remains, the ownership and stewardship of cultural heritage, and the impact on descendant communities
• The excavation and study of human remains must be conducted with respect, sensitivity, and consultation with relevant stakeholders
• The removal of artifacts and features from their original context can be seen as a form of cultural appropriation or loss, particularly for indigenous or marginalized communities
• Archaeologists have a responsibility to engage with and benefit the communities whose heritage they are studying, through collaboration, education, and capacity building (Developing a memorandum of understanding with an indigenous community regarding the excavation and curation of ancestral remains)