Dig Deeper Blog,  Exhibits

Dig Deeper: How Old is It? Absolute 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.

Introduction

Now that we have discussed debitage, the waste left behind during tool creation, let’s dig deeper and learn about absolute dating.

Absolute Dating vs. Relative Dating

Absolute dating is the science that allows archaeologists to determine definite dates for artifacts. For example, if coins are found during an excavation, the coin is (usually) stamped with a date, and archaeologists are able to use the date stamped on the coin to determine when it was made and when it is from.

When artifacts are found that can be dated this way, other artifacts found at the same site are also dated but by using relative dating. Relative dating uses the dates of artifacts with absolute dates and infers that the other artifacts found are from around the same time and we will explore this further next month.

These types of dating techniques can be useful for archaeologists, but many times, artifacts found at sites have no dates stamped on them at all. So how do they decipher the age of an artifact like this?

Carbon-14 Dating

Scientists use a mass spectrometer for Carbon-14 dating

Another form of absolute dating is called Carbon-14 dating. This type of dating can be used to date organic artifacts. An organic artifact is an artifact that once was living, like bone or shell. Carbon is an element that is absorbed by all living things during their lifetime. A regular carbon element has an atomic weight of 12. To break it down even further, carbon is made of six protons and six neutrons. (To learn more about atoms, protons, and neutrons watch this video on YouTube.)

Carbon-14 is different from carbon in that it is an isotope of carbon. Chemical elements have one or more isotopes and these are defined as, each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons. Carbon-14 has two extra neutrons, giving it an atomic weight of 14 with six protons and eight neutrons.

So, carbon is absorbed by all living things. When a plant or animal dies, the number of carbon-14 atoms start to decline. Scientists and archaeologists know the rate of decay, which helps them to measure the remaining carbon-14 in the object and helps to determine how old it is. Carbon-14 dating can be used for organic objects that are 500 to about 50,000 years old.

An example of carbon-14 dating on shellfish

An example of this carbon-14 dating method is seen in the image to the right. After the shellfish dies, the carbon-14 atoms begin to decay. Carbon-14 has a half-life of 5,730 years, so there would be half as many carbon-14 atoms present in the shell after 5,730 years. By counting how many carbon-14 atoms remain, it can be determined when the shellfish was alive.

Up Next

We have learned about some techniques involving absolute dating, but how do archaeologists use relative dating? Come back next month to dig even deeper and learn more about relative dating!

By Jessica McPheters, Collections Manager

Learn More

Archaeology 101 Exhibit

 

Collections Research

With the assistance of Center staff, the intern will identify, design, and conduct an original research project that uses the Center’s archaeological collections. The intern will formulate a plan for public dissemination of the project results as a journal publication, a museum exhibit, or a public class or lecture. During the course of the research and dissemination planning, the intern will receive training in research design, collections management, artifact analysis, and exhibit design and production as appropriate to the selected project.

Archaeology Lab Positions

Volunteers will prepare one or more archaeological collections for curation. Center staff will instruct the volunteer on archaeological laboratory procedures such as basic artifact analysis, manual and computer cataloging, storage requirements, and preventative conservation.

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.

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; tour web app content creation, integration, and management; 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

With the assistance of Center staff, interns will research, design, and produce a project that educates the public about archaeology or a related field using the Center’s archaeological collections. Interns may create virtual museum exhibits and related activities, develop curricula for K-12 programs in line with current content standards, or plan and present a public class or lecture. Per approval, special projects of the intern’s choosing are also available. During the course of the research and planning, the intern will receive guidance as appropriate to the selected project.