Dig Deeper Blog,  Exhibits

Dig Deeper: How Old is It? Relative Dating

Dig Deeper is a monthly blog focusing on the basics of archaeology by taking a closer look at the exhibition Archaeology 101, which is currently featured at the Center.


Last month we discussed absolute dating, the science that allows archaeologists to determine definite dates for artifacts; let’s dig deeper and learn about RELATIVE DATING.

How Do Sites Become Buried?

People are generally surprised at the amount of dirt covering archaeological sites. Artifacts and features that archaeologists study have often been abandoned for hundreds and thousands of years. Weather, animals, vegetation, and you guessed it – HUMANS – contribute to the burial and layers uncovered while excavating sites.

Dust and debris may cover remains of a site when it is windy, or perhaps floods bring silt and soil, or during catastrophic events like Pompeii or Herculaneum, sites may be covered quickly and completely by ash and volcanic mud. Before environmental laws were in place, many humans would build over archaeological sites unknowingly — filling in holes to create a surface level in which they could then build upon. There are many attributes that bury history over time.


While artifacts and sites may be found by doing a survey of the surface area, in general most artifacts and ecofacts that archaeologists find are buried underground. Most archaeological sites have many layers corresponding to each event that added soil, dirt, and debris to a site. These different layers are referred to as strata. The deeper the strata, the older it is and the newer, or younger strata are found towards the top.

How Absolute Dating Can Aid Relative Dating

If you read last month’s blog then you know that when artifacts are found and can be dated using a form of absolute dating, like Carbon-14 testing, the other artifacts found at the same site may be dated by using relative dating. One way to use relative dating in conjunction with absolute dating is by assuming that the dates of artifacts found at a site are from around the same time.

Using Stratigraphy to Date Artifacts

This also applies to stratigraphy (or the study of strata). If an artifact is found between two layers of strata, it can be assumed that the artifact is older than the layer above it and younger than the layer below it. This allows archaeologists to determine ages for the layers above and below the artifacts, and not necessarily for just the artifact itself. By using this method, many artifacts can be dated by looking at the strata surrounding them.

If there are artifacts that have known dates in a strata this is even more helpful because for example, if an artifact is found in the same layer as a flip phone, we can infer that the layer dates from 1989 or newer because flip phones were first introduced in 1989.


This concludes the Dig Deeper blog. We hope you learned a lot and can visit the exhibit Archaeology 101 in person soon. In October we will be back talking about ARCHAEOLOGY MONTH. Look forward to “seeing” you then!

By Jessica McPheters, Collections Manager

Learn More

Read more about the ancient Roman sites of Pompeii and Herculaneum.

Archaeology 101 Exhibit
Dr. Arty Fax’s Archy Facts


Volunteers work in the Center’s Research Library, cataloguing materials and organizing on a computer-based system.

Marketing and Administrative Volunteers assist the Development Office or Administration Office with data entry, updating marketing materials and clerical tasks. Computer experience is a plus.

Docents welcome visitors and answer general questions regarding the Center and exhibits. Docents staff the gift shop and help out with administrative and curatorial tasks.

Volunteers support event activities at the Center, such as the Annual BBQ, lectures, workshops, and fundraising events. Be a part of the party!

Volunteer provide support for K-12 programs offered at the Center. These are fun, hands-on programs that kids really enjoy. Teaching experience is a plus, but not required. Background checks are required.


With the assistance of Center staff, the intern will use photogrammetry to prepare one or more archaeological collections for digital preservation, as well as create a virtual museum exhibit for our Public Archaeology department. Per approval, special projects of the intern’s choosing are also available. During the research and planning, the intern will receive guidance as appropriate to their selected project. Prospective interns should already be familiar with photogrammetric procedures, and Agisoft Metashape.

Collections Management

With the assistance of Center staff, the intern will prepare one or more archaeological collections for curation. During the course of the internship, the intern will learn to identify artifacts and ecofacts common to the San Diego region, including lithics, ceramics, historical objects, and faunal, botanical, and mineral specimens. Center staff will instruct the intern on archaeological laboratory procedures such as basic artifact analysis, manual and computer cataloguing, storage requirements, and preventative conservation. In addition, the intern will become familiar with historical trends in archaeological practice in the San Diego area and will be introduced to current legal and ethical issues in archaeological curation as well as the concerns and rights of culturally affiliated groups with regard to archaeological materials.

Development and Marketing

Under the direction of Center staff, the intern will support the department in various activities, including, but not limited to, fundraising and grant research; e-newsletter development; social media marketing; and website maintenance. This internship will give the intern valuable, real-world experience in non-profit fundraising and marketing.

Geographical Information Systems in Archaeology

Prospective Interns must have completed three courses: Introduction to GIS, GIS Database Management, and Intermediate/Advanced Methods in GIS. The intern will be assigned a project where they will create shapefiles and maps for curated archaeological collections, museum exhibits, and/or public outreach using ArcGIS 10.6. Center staff will instruct the intern on archaeological GIS laboratory procedures such as computer cataloguing, storage requirements, and database management.

Library Science

With the assistance of Center staff, the intern will arrange and catalog materials in the Center’s library. During the course of the internship, the intern will take a leading role in the cataloging, sorting and storing of research files and creating user guides for these collections. Center staff will instruct the intern on archival procedures, computer cataloging, storage requirements, and preventative conservation.

Public Archaeology

Harness your passion for Public Archaeology and gain hands-on experience with K-12 museum field trips, lectures, and public outreach. Additional projects may include creating virtual museum exhibits and activities, assisting in the development and implementation of K-12 curricula programs, planning and presenting public facing content, or educational field trip content of your own design. Must be able to pass a Live Scan.