Maritime Heritage: Archaeological Survey at Rodanthe

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What is Maritime Heritage?

For much of human existence, people have relied on water as a source of food, energy, transportation, and even recreation.  A narrative of human interaction with bodies of water throughout the course of history are preserved not only in writing, but also in physical objects left behind.  These objects, called material culture by archaeologists, can relay information about the culture of the people that made and used these objects; they can tell us something about ourselves and our shared heritage.  Although we have written records that help inform us of our past, these are often incomplete.  Archaeologists help plug some of the gaps by studying the material cultural remains for clues about their use, value, and meaning.  Maritime heritage is the study of our past in the context of marine environments.  It is about how we used, worked, traveled, and played in, on, and under water.

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Herman Moll Map, 1746

Why is it important?

Knowing where we come from and where we have been can help inform us of where we are going.  The study of history and of people in the context of the maritime world can also offers some advantages.  Objects that are submerged (found underwater) can sometimes be in an exceptional state of preservation.  Despite the passage of years, decades, and even centuries, some objects found beneath the waves look much like they did when they were first lost.  The better the state of preservation, the more an archaeologist is capable of extracting information from the object.

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John Lawson map, 1709

People relied on ships, boats, ferries, flats, and barges to carry cargo, livestock, passengers, and personal belongings.  We hunted whales and walruses, sharks and skates.  We used ships to cross oceans, to find new lands, to explore and interact with new cultures and we used them for war.  Sometimes these varied crafts did not reach their destination.  Bad weather, poor directions, leaky planks, hidden shoals, big waves and shallow water, cloudy skies and sudden squalls could sink a boat and often did.  These vessels went down with all that they contained still in their hold and could sit for centuries before they are rediscovered.  An archaeological study of a shipwreck is a study of culture in a confined space, a microcosm of a larger society.  Not only are the objects found on the vessel helpful and worthy of study, but the ship itself reflects cultural adaptations, innovations and technological advancements.

These submerged artifacts are resources to researchers and can be a source of information to help us answer questions we have about our past.  Like some natural resources, these maritime artifacts are finite and in need of protection.  Once the context of an archaeological site is destroyed, there is no reassembling it and the information that it can offer is severely diminished if not lost forever.

 

Maritime Heritage Survey

Archaeologists at UNC Coastal Studies Institute, instead of focusing their efforts on shipwrecks alone, approached this project with a broad consideration of the ways that humans may have impacted this area over time.  This expansive view gave way to a focus featuring four categories of research which included: 1) impacts from dredging, 2) impacts from commerce, 3) impacts from conflict, 4) impacts from marine accidents.  By doing so, researchers hoped that these areas could highlight potential archaeological sites or give context to archaeological finds in the event of their discovery.  In addition, this approach afforded researchers the opportunity to divulge the history of an area that has never been the subject of an extensive historical investigation.

 

Methodology

 STEP 1: Historical Research

This project, like any thorough and proper archaeological survey, began in the archives where researchers accessed documents, records, letters, wreck reports and other historical information to carefully comb for clues.  Starting with the general and narrowing to the specific, researchers began first with regional histories found in secondary sources and whittled down to wreck reports of first-hand accounts recorded by the United States Life-Saving Service at Chicamacomico.  In consulting a broad array of sources, researchers could contextualize the fluid economic and social conditions that occurred in the larger landscape in order to see if similar activities took place in the Rodanthe research area and provide potential archaeological site locations within that boundary.

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Researchers examine a digital map featuring the research area.

 Step 2: Historic Maps and Geographical Information System

Due to the dynamic nature of the shifting sand banks on the coast, cartographic sources, such as historic maps, illustrate the hazards encountered by contemporaries of various times in history.  By identifying hazards, archaeologists can potentially pinpoint significant areas of risk where mariners may have run into trouble navigating.  Additionally, by comparing maps throughout history, researchers can examine shoreline change through time which may have impacted archaeological remains.  A landscape in flux means that which was once underwater could now be found on land and that which was high and dry may now be resting beneath the sound. Geographical Information System (GIS) is a computer software that researchers use as a tool to overlay these maps on top of one another for comparison.  The process by which these maps are overlayed relies on selecting specific points on the historic map that line up with a modern basemap.  In addition, examining these maps also showcases changing cartographic symbols within the research area, which reveals clues to wrecking events and evolving landscape use.  This preliminary research that occurs before archaeologists even enter the field is crucial to maximizing the productivity of the field survey.

Step 3: Side Scan Sonar and Magnetometer Survey

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A research vessel tows remote sensing equipment near Rodanthe.

Maritime archaeologist rely on remote sensing technology to cover large swaths of submerged areas in a methodical and systematic survey.  For this project, archaeologists utilized two different remote sensing technologies simultaneously to gain a greater sense of what physically remains on the sound floor or a few meters beneath it.  Side scan sonar emits sound waves in the form of a Compressed High Intensity Radar Pulse or CHIRP, which bounces off the underwater floor and returns to the receiver.  Any objects that sit off of the bottom appear on a computer screen aboard the research vessel in the form of relief. It is up to the team of archaeologists to interpret these images and ascertain significance and sites of potential interest.  Researchers also used a magnetometer in concert with side scan sonar to aid in the survey process.  A magnetometer detects distortions in the earth’s magnetic field, which is useful because objects that are capable of distorting the earth’s field are ferrous, meaning they contain iron.  The presence of iron often indicates objects that were constructed by humans such as ships, docks, piers, and duck blinds.  Magnetometers offer the added benefit of detecting ferrous objects buried beneath the sand, providing the opportunity for anomalies or areas of interest not picked up by the side scan sonar.  The survey covered an area of 2.5 kilometers by 2.5 kilometers of sound floor.  To cover that much ground in an efficient and exacting manner, the researchers designed a line spacing grid that allowed for 200% coverage of the sound floor.  This meant that each square meter of the sound, within the research area, was remotely surveyed from two perspectives.  To carry out the survey, researchers performed what is commonly known as “mowing the lawn”.  Beginning at a Global Positioning System (GPS) fixed point, researchers set a heading and follow that heading for 2.5 kilometers.  When they reach the end of the survey area, they position the research vessel over 25 meters to begin another lane, heading in the opposite direction in which they just came, much in the same manner you cut the grass in your yard.  The work is not over upon completion of the survey portion of the project, in many ways it has just begun.  Archaeologists need to assemble the data and perform a set of procedures called post-processing.  This is an opportunity to refine the data and identify anomalies or objects of particular interest.

Step 4: Shoreline Transect Survey and Metal Detection

In areas too close to shore where the remote sensing equipment could not go, the team performed a shoreline transect survey.  This portion of the research was not designed to be a comprehensive survey covering the entire shoreline, but rather just a sample.  The team established a survey grid comprised of a 600 foot by 600 foot section once again defined by GPS units.  In the event of an archaeological find, the researchers could pinpoint its location within the grid with an excellent degree of accuracy.  The team laid a baseline measuring 300 feet long and ran it on a direct northerly course to help construct their grid.  The process by which the team surveyed this sample area followed the same principle as the remote sensing, except this survey was a visual inspection, meaning they “mowed the lawn” using sight rather than equipment, because the water depth allowed it.  When the visibility became poor, sense of touch took its place.  When the water became too deep, the archaeologists donned masks and snorkels.  During the shoreline transect survey, as team members conducted visual inspections, one of the members carried a metal detector.  This waterproof device, unlike the magnetometer, is capable of detecting other non-ferrous metals, while also collecting GPS positions for each anomaly.

Step 5: Photogrammetry

This portion of the research is ongoing.  Visit this site again for future updates on the Rodanthe project.