Changing Planet

Colonial Shipwrecks of Colombia: Magnetometer Survey of Bahía de la Gloria and Isla Tarena

Archaeologist Bert Ho runs tows the magnetometer from our survey boat, while monitoring the readout and incoming results on the Panasonic Toughbook with the differential GPS mounted on a bamboo pole.
Credit: Andres Diaz/The Meadows Center for Water and the Environment at Texas State University

National Geographic Grantee and Texas State University Research Faculty Frederick “Fritz” Hanselmann and a top-notch team of archaeologists from Colombia and the United States are leading an expedition to locate and document historic shipwrecks off of the Caribbean coast of Colombia. Follow along with Fritz’s updates from the field. 

While Chris, Juan, and I were busy mapping the possible seawall in Bahía de la Gloria, Bert and Andres began the magnetometer survey in and around the bay and Isla Tarena.  Electronic survey is one of the first steps to locating potential shipwreck sites.  In areas with high rates of sedimentation such as river mouths and bays, a magnetometer is often the best tool to read into the sediment on the seafloor.   As mentioned in an earlier post during our work off of Cartagena, a magnetometer functions similar to a metal detector, but has a much higher sensitivity, able to detect large metallic signatures, or anomalies, in the magnetic signature of a given geographic region.  The magnetometer allows us to conduct geophysical and electronic mapping.  What this means for us as archaeologists is that we have a tool that is extremely useful for finding historic shipwrecks as many of them have different characteristics and features that are made of iron.  The mag is towed from the stern of the boat and the boat is driven in lanes predetermined in the GPS and survey software, which allow us to cover an area accurately and efficiently.  If you notice in the picture above, we’ve had to take a certain license to rig up our panga to function as a survey boat, yet it worked great!
Bathymetric mapping results of our initial magnetometer survey in Bahía de la Gloria.  The red indicates the possible wall. Credit: Bert Ho/The Meadows Center for Water and the Environment at Texas State University
Initial bathymetric results of our initial magnetometer survey in Bahía de la Gloria. The red indicates GPS waypoints on the possible wall.
Credit: Bert Ho/The Meadows Center for Water and the Environment at Texas State University

In the case of Bahia de la Gloria, we only have a slight idea as to the kinds of ships that have wrecked in the area, i.e.: merchant or naval vessels, but the magnetometer will help us identify areas of interest to conduct diver visual surveys and determine if there is any material culture that creates the anomaly or signature. Once we’ve surveyed an area, we process the data that we’ve acquired so that we can understand where potential cultural resources might be buried and the overall topography and bathymetry of the seafloor in a project area.  After the initial processing of the data with the few hours of electricity that we have per day, we start to plan our next dives to explore the anomalies that show up in the results.

Frederick "Fritz" Hanselmann is Research Faculty, who serves as the Chief Underwater Archaeologist and Diving Program Director with the Meadows Center for Water and the Environment at Texas State University. He is also the director of The Meadows Center's Underwater Archaeology and Exploration Initiative. Fritz learned how to swim at age three, and has been in love with the water ever since, having been taught to breath hold dive by his grandfather diving for golf balls tied in a sock in the Gulf of Mexico. Having worked on underwater sites from a wide variety of time periods, his research ranges from submerged prehistoric deposits in springs and caves to historic shipwrecks in Latin America and the Caribbean, including the wreck of the Quedagh Merchant, abandoned by Captain Kidd in 1699 off the coast of Hispaniola. Fritz led the first-ever archaeological survey of the mouth of the Chagres River in Panama as the initial phase of the ongoing Río Chagres Maritime Landscape Study. One aspect of this study is the Lost Ships of Henry Morgan Project, the search for the famous privateer's sunken ships. He is one of the Principal Investigators of the Monterrey Shipwreck Project in the Gulf of Mexico, which is the deepest shipwreck excavation ever conducted in North America, in collaboration with three federal agencies, three universities, and three non-profit organizations. Fritz is also the co-director of the Sunken Ships of Colombia project, which focuses on finding, documenting, studying, and managing historic shipwrecks along the Caribbean coast of Colombia. The Spring Lake Underwater Archaeology Project on the university's campus also falls under his supervision and he assists other projects in Mexico and Texas as part of the Initiative. Fritz also focuses on capacity building and training for archaeologists and heritage managers in less developed countries, as well as the development of marine protected areas and underwater preserves. He is a GUE Cave and Technical Diver, a Nautical Archaeology Society Tutor, a certified scuba instructor, an ambassador for Aquadive Watches, and a fellow of the Explorer’s Club. Fritz regularly gives public lectures and presentations for museums, universities, and other organizations.

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