Conservation: Underwater Sites

By Katherine Hodge, Public Education Coordinator

In this series so far, we’ve looked at how well artifacts are preserved in wet and dry environments. From textiles preserved in peat bogs to paper in Egyptian tombs. However, have you ever thought about how well archaeological sites and artifacts can be preserved underwater? Today, we look at how well sites are preserved underwater and what these conditions mean for artifact conservation.

Humans have been using bodies of water like oceans, lakes, and rivers as sources of food and transportation for tens of thousands of years. All of this human activity on the water eventually led to submerged archaeological sites and shipwrecks. Many of these fascinating sites and artifacts have been found by archaeologists. Underwater sites, like shipwrecks or structures that slid into the ocean, are especially valuable sources of data because many capture a moment in historical time rather than being composed by layer after layer of occupation.

Shipwrecks

Though a wreck may not sound like something of huge archaeological value, they have the potential to contain valuable pieces of data. By excavating a shipwreck, archaeologists can learn a great deal about important trade routes and goods of the time period, the seafaring technology available, and the details about relationships between many countries.

A small replica of what the Java Sea shipwreck may have looked like (Made by Nicholas Burningham for the Field Museum)

One excellent example of valuable data from a shipwreck is the Java Sea Shipwreck at the Field Museum in Chicago. The wreck itself is around 800 years old, and it was discovered in mostly intact and in great condition. This gave archaeologists a unique glimpse into trade and seafaring history, and they began excavating the site in 1996. The Java Sea Shipwreck contained trade goods from China that were on their way to Indonesia. There were thousands of artifacts, but some of those discovered were valuable porcelain, resins, and even ivory.

Not everything survived in this shipwreck while it was underwater. The wood of the ship disintegrated away and the metal bars became corroded lumps of minerals and sand.  However, even with the sea destroying some of the site, it also had a unique way of preserving it. As the ocean corroded away the metal, chunks of minerals and sand formed on top, creating a sort of negative of what was once there. The empty space without clumps of sand or minerals shows archaeologists where metal once was.

The Conservation of It All

Though artifacts can survive underwater for long periods of time, their conservation differs a great deal from the conservation of objects that are found on land. Artifacts that have been underwater for a long time can be extremely delicate and removing them takes time and experience. Conservators and archaeologists have to study for a long time to learn how to do the complex excavation and stabilization process that ensures their survival for generations to come.

When underwater artifacts are removed from their context and placed on land, they are no longer submerged in water. This change from waterlogged to dry can result in certain types of artifacts disintegrating completely because they are too

A member of Diving With A Purpose on the job

fragile. Others can break and crack due to the sudden lack of moisture. To avoid such damaging changes, conservators will do their best to keep the object in equilibrium and maintain stability, adding things or changing conditions only when it will promote the object’s longevity. It is also important to remember that it is not just the preservation of the object itself that is important, but also the preservation of the data within the object. DNA, chemical composition, isotope analysis of teeth and bones, and XRF analysis can all contribute a wealth of information to the archaeological record, but only if that kind of data is still present in the artifact.

Sometimes, taking an artifact out of the water is not possible because there is a high likelihood of it not surviving on land. Other times, a site is too big and can be studied in a more robust and complete manner by archaeologists diving down. In these special cases, sometimes archaeologists will make underwater museums and memorials for others to dive on and learn from.

One example of this is from Diving With A Purpose, and organization that does incredible work at locating, excavating, researching, and protecting shipwrecks from the African slave trade as well as other underwater archaeological sites. They document sites and artifacts, and members of the organization have helped put underwater plaques and markers down near sites to mark their significance in history.

Another example of this kind of choice is the Baia Underwater Archaeological Park. This underwater part is located in Naples, Italy and consists of a huge, submerged archaeological site of villas, the old port, and other structures. This port became submerged in the bay around 1500 years ago, but it is extremely well preserved and in very shallow waters. This makes it an ideal site for archaeologists to excavate in order to learn more about Roman trade and architecture. As a park, there are also areas of the archaeological site that tourists can scuba dive through, seeing well-preserved statues, intact and beautiful mosaics, and other architectural features. This kind of preservation not only allows visitors to literally submerge themselves in history and archaeology helping them understand the value and important of site stewardship.

Underwater preservation poses unique challenges to conservators, who must work to stabilize artifacts that have been under the sea for hundreds and even thousands of years. Next time you look out to the ocean, a nearby lake, or a local river, think about all the archaeological sites and artifacts that are just below the surface, waiting for archaeologists to carefully study one day.

 

https://www.nationalgeographic.com/culture/article/most-slave-shipwrecks-overlooked-until-now

https://divingwithapurpose.org/

https://ncseagrant.ncsu.edu/coastwatch/previous-issues/2013-2/winter-2013/the-science-of-shipwrecks/

https://www.fieldmuseum.org/blog/what-were-still-uncovering-800-year-old-shipwreck

https://www.mnhs.org/sites/default/files/lhs/techtalk/techtalkjanuary1997.pdf