Trick question: where do you look for a 10,000 year old beachside settlement in Southeast Alaska?
Could be near the beach … but more than likely it’s three miles inland, 750 feet above sea level, or somewhere in between.
Glacial rebound is especially pronounced in inland northern Southeast Alaska. But what glacial rebound obscures, shoreline modeling and Tlingit oral narratives can help clarify.
Forest Service Geologist Jim Baichtal has been working on a better way to locate cultural sites for the last 25 years. University of Alaska Southeast Associate Professor of Anthropology Dan Monteith has been working with Southeast Alaska’s ancient cultural sites since the mid-1990s.
In southern Southeast Alaska, researchers can sometimes literally trip over findings on the beach, Monteith said. Northern Southeast Alaska is different.
“Here, you’re going to be up in the hinterlands, so to speak,” he said.
“What became apparent was the incredible differences that you see across Southeast Alaska,” Baichtal said.
Those differences are related to how heavy a layer of ice may lay across the landscape, or how much an advancing glacier pushed up the land in front of it, during the last glacial maximum.
When the ice started to recede, the land that had been beneath the glacier began to decompress and rise, a process known as glacial rebound. In contrast, the land that had been pushed in front of the glacier, especially islands on the outer coast, began to sink, and ocean levels rose — something consistent with Tlingit oral history, which describe tides rising in some locations.
In Juneau, Baichtal estimates about 840 total feet of glacial rebound over the last 13,000 years. In Ketchikan, in contrast, that number is 470 feet. Around Petersburg and Wrangell, it’s 400 feet.
This indicates, Baichtal said, that glacial ice was about half as thick there as compared to Juneau.
Around Prince of Wales, Southern Kuiu, Baranof and westernmost Chichigof, that amount is about 60 feet, he said.
“There was always this huge dichotomy” between the mainland and the outer islands. “If you can figure out where those paleoshorelines were, and where resources were available, you can predict where early habitation sites are,” Baichtal said.
The rate of rebound influence from the Little Ice Age has made northern Southeast Alaska more difficult to predict and figure out, Monteith said.
“Part of it’s figuring out where to look,” he said. “It’s a little counterintuitive.”
Baichtal, Forest Service archaeologist Risa Carlson and others have developed a model that uses Geographic Information Systems and digital elevation models to “flood the landscape.”
Before they applied the model for the first time in 2009, researchers had found only five cultural sites in Southeast Alaska dated at more than 7,000 years old. Most had been found through road construction, timber harvests, foundation digging, or another kind of disturbance.
Since applying the paleoshoreline model, they’ve found 12 new sites by predicting where they might be. They’ve also redated one known site, for a total of 18 ancient locations.
“It’s a whole different way of going about it,” Baichtal said. “We’re looking in places that are totally different from where we would have looked.”
Findings, oral histories
Last May, Monteith taught a class in which students looked for raised marine beaches around the Juneau-Douglas area.
For the most part they found shell clusters, clay, organic materials and sharp bits of rock. They dated those shells to hone the shoreline model.
The UAS campus has “incredible” potential, he said.
In southern Southeast Alaska, researchers have found a number of different types of fish hooks.
Other finds: An 800-year-old small fish weir found on Montana Creek in the 1990s. There are more than 100 weirs in southern Southeast.
They’ve found basketry material on Baranof and Prince of Wales islands that’s 6,000 years old.
“For me one of the exciting things is just seeing how the Tlingit oral narratives are kind of being reconfirmed or verified through geological, geoarcheological work,” Monteith said. “It’s really about trying to understand some of the early habitation and migration of people through and along the coast. I take these oral narratives as oral histories. They tell us the movements and histories of these people — where people lived, camped, fished, worked the land — and how they worked the land and the waterways, too. I definitely think scientists should give these oral histories a lot of credence.”
Baichtal said they’ve found a lot of “microblades” — paper-thin stone blades that were inset in bone or antler to create a serrated edge. They’ve also found a large deposit of charcoal in 73 places, leading to the conclusion Southeast Alaska may have been more susceptible to forest fires, as a warmer, drier, place, prior to the onset of today’s rainforest weather. That’s consistent with pollen records and findings in other areas, as well. It may have been two to three degrees warmer, with half today’s rainfall.
“People were probably sitting down having drinks with little umbrellas on those beaches,” Baichtal joked.
Glacial rebound has an impact even with recent sites. Take Sawmill Creek in Juneau, for example, which is an area with a historical record of barges loading canned salmon about 100 years ago. Now, this area is “high and dry,” a quarter of a mile into the forest, Monteith said.
Monteith also studies how landscape change impacts salmon runs and human activity in northern Southeast Alaska.
“It’s trial and error and guesswork — like any science,” Monteith said.
Archeologists from the U.S. Forest Service’s Juneau Ranger District, along with other scientists, have also been working on the project.
Monteith would like to do more work on Admiralty Island.
“Admiralty is just amazing,” he said. “I think we could learn so much by doing more archeological work on Admiralty, just because of its monument status — there the rebound is much more subtle, but I think Admiralty may yield as much information as a place like Prince of Wales Island.”
Admiralty is important as a historical crossroads, as well.
“If you were living here since time immemorial, that was an incredibly productive, rich, beautiful place to live,” Monteith said.
He also anticipates continuing to research and find sites around Douglas and Juneau. His spring class at UAS will clean samples from Juneau and Douglas at a variety of locations. They’ll send six to eight samples off for radio-carbon dating.
Baichtal expects the shoreline modeling project to go on “forever.”
“It gets you close,” Baichtal said. “It gets you into the realm of possibilities. It’s exciting stuff.”
• Contact Outdoors reporter Mary Catharine Martin at firstname.lastname@example.org.