Underwater Archaeology Reopens the Gateway to the Americas

The earliest people to set foot on North America most likely did so by journeying across a land bridge that connected present-day Alaska and Russia. Today, archaeologists study exactly how these ancient people completed their journey, and what traces of their migration they left behind. Earlier this year, with support from the National Science Foundation (NSF), the Gateway to the Americas project began its second phase of data collection to search for answers to some of these questions.

James Dixon—anthropologist, Gateway to the Americas principal investigator and director of the University of New Mexico’s Maxwell Museum of Anthropology—and Kelly Monteleone—a doctoral student researcher with Dixon—are using novel methods to test the theory that people entered the new world via a coastal migration route along the continental shelf of southeastern Alaska. This is a difficult scientific endeavor, because this area is now under roughly 160 meters of water as a result of changes in sea level.

"The primary objective of this research is to develop and refine methods for identifying and sampling ancient underwater archeological sites on the continental shelf,” Dixon explained. “We are specifically searching for sites, such as small settlements, that were occupied by people prior to the dramatic rise in sea level that occurred at the end of the last Ice Age, between about 16,000 and 10,000 years ago."

Dixon and Monteleone are using a combination of underwater acoustic imaging data, landscape modeling and a remotely operated vehicle to search for the remnants of these immigrants with the hope of understanding what life was like for these travelers.

A New Model

Now in its second year, the first phase of the project began in 2010 and tested methods and modeling techniques that are not routinely used by marine archaeologists in North America.

“We developed a predictive model that we tested using geophysical techniques, such as side scan sonar and Van Veen grab sampling.  Our initial results are very promising, and indicate that these methods are a suitable test for the presence of archaeological sites at depths of at least 50 meters.” Monteleone explained. “We also have an ROV—a remotely operated vehicle—with cameras and lights that dives down to the sea floor. With the ROV, we were able to visually inspect areas where the sonar suggested there might be archaeological features.”

Using geophysical data, as well as ethnographic and archaeological information, Monteleone’s model is able to reconstruct what the landscape may have looked like before the area was flooded 10,000 years ago.

Phase two received NSF funding in 2011 and the first season of fieldwork kicked off in May 2012. Efforts focused on Shakan Bay and the Gulf of Esquibel; both areas are close to known terrestrial archaeological sites.

Navigating the 40-80-meter waters by boat, the researchers use acoustic imaging technology (sidescan sonar and multibeam echosounders) to draw detailed images of the sea floor that would include any potential maritime archeological features. This, together with Monteleone’s landscape model and the sediment data, let the team pinpoint areas of interest that can later be explored with the ROV.

"These methods provide an efficient and relatively safe method to survey large areas of the ocean floor,” Dixon said.

Sunken Secrets

So far what they’ve found using these techniques is eye opening. Initial analysis of the sediments uncovered pieces of wood, pinecones, a thick layer of broken shell called shell hash, and a curious fragment of wood currently undergoing radio carbon dating. The team also discovered what was first thought to be a fishing weir, but further analysis proved otherwise.

According to Dixon, "What appeared to be an alignment of stones that was tentatively interpreted in 2010 as the possible remains of a stone fish weir, were reinvestigated in 2012.  Based on the results of this more comprehensive survey, it appears that this distribution of stones on the ocean floor is probably not cultural in origin.  However, the discovery of an undated fragment of cut wood and unusually high frequencies of shellfish remains suggest that this locale may warrant further investigation."

In 2010 the team also stumbled upon something that’s not nearly so old. While surveying, they located a shipwreck that sank in 1910. The wreck was found just off a peninsula near the study area.

There are no plans to preserve or excavate the shipwreck artifacts. “With underwater archeology in general, the main action plan is to leave sites in situ, as they are currently. We’ll be doing sampling first to identify the site and second for dating purposes,” she said. “We’re not excavating. We just want to identify the locations.”


Another unique characteristic of the Gateway to the Americas project is the sheer size of the study area. Dixon and his team are modeling the landscape of more than 45,000 km2 in all. That’s an area slightly larger than the state of Ohio!

There are many partners with a range of expertise contributing to the project’s success. They include ROV technicians who operate the vehicle and troubleshoot any quirks while in the field and under less than ideal conditions; multibeam echosounder and sidescan sonar specialists from Kongsberg; and research support provided by Sealaska Heritage Institute student interns. Sealaska is a nonprofit Alaskan Native institution. Over the next several years, Dixon and his team will continue to survey the sea floor to locate evidence that tests their coastal migration hypothesis.

"In cooperation with the Sealaska Heritage Institute (the regional Native American organization), we plan to extend our surveys in 2013 to other promising areas of the continental shelf of Southeast Alaska,” Dixon said.  “One area that is particularly exciting is near a source of obsidian (volcanic glass) that we know was used by people at least 10,000 years ago.  There may be evidence indicating even earlier use of that obsidian source preserved in the nearby ocean sediments.” –Alicia Clarke