Approaching the beach town of Goderich, Ont., you’ll travel through rolling farmland and pasture. Suppose that once you reach Lake Huron, you continue northeast towards Michigan. Travel past the sandy beaches, and plunge below the clear water to the lakebed to ride along a shallow ridge with two deeper basins flanking either side. In this spot roughly 10,000 years ago, you would have been standing on dry land. And if you listened closely, you probably would have heard the thundering of caribou hooves, or the celebration of a successful hunt.

In the early 2000s, John O’Shea, an archeologist at the University of Michigan, first spotted this conspicuous ridge running the width of Lake Huron, from Alpena, Michigan, to Amberley, Ont., on a detailed bathymetric map. A boat trip using side-scan sonar revealed structures along the ridge that appeared to be human-made. His team of researchers and divers quickly began exploring the Alpena-Amberley Ridge. At the Drop 45 site, they identified a series of stone structures where migrating animals would have bottlenecked on the once-dry ridge, including stacked stones that created a “funnel lane” to corral caribou and blinds where hunters would await their prey unseen.

To explore the now-submerged landscape, dive teams guided by an underwater remote-operated vehicle dubbed “Jake” collected sediment near the structures. Lisa Sonnenburg, then a professor at McMaster University in Hamilton and an expert in reconstructing paleo environments (ancient landscapes), began reconstructing the composition of the ecosystem from amoeba fossils and pollen in these sediment samples. Her team discerned that the ecosystem around the ridge and hunting blinds would have resembled the present-day Hudson Bay Lowlands, with white pine forests and peatlands.

And the sediment continues to reveal the secrets of this submerged landscape. Brendan Nash, a graduate student at the University of Michigan, recently reexamined two unprocessed flakes from a stone tool. Analysis revealed the stone was actually obsidian and likely originated around 9,000 years ago in central Oregon — more than 4,000 kilometres away. Finding these stone flakes so far from their origin indicates there were social networks across the continent much earlier than previously thought. “Trade networks existed across Europe at this time,” says Sonnenburg. “Why wouldn’t they be in North America?”