Written by: By Dr. Todd Kristensen, Archaeological Survey of Alberta
Archaeologists compare records before and after ancient volcanic eruptions to understand how the lives of people changed. Impacts of ecological disasters on humans can be detected along local and broad scales: how did Indigenous people cope at a specific site and how did human relationships change across vast regions? A massive eruption 1,200 years ago, called White River Ash East, changed the way that people in northern Canada hunted and gathered in areas affected by volcanic ash, which fell in beds up to 1 m thick. Beyond the ash footprint, human networks were forever altered, with ripple effects that spread through Alberta and North America.
Environments
Airborne plant pollen and charcoal preserved in cores of lake muds reveal how vegetation changed after the eruption. Pollen indicates the species of plants that formed local forests, while charcoal levels tell of former wildfires. From there, archaeologists work up the ancient food chain from fires and forests to fish and game to understand how Indigenous diets were disrupted during ecological catastrophes.
Livelihoods in Yukon and Northwest Territories were probably affected the most by impacts of volcanic ash on caribou and fish. Ash would’ve smothered low-lying plants that caribou relied on. Northern plant communities (including reindeer lichen) can take many decades to re-grow after disturbance. The ash, which is made of tiny glass particles, also would’ve caused eye problems, blocked digestive tracts, and led to animal tooth wear that resulted in malnutrition or death. Volcanic ash in water systems reduces oxygen available to fish, scratches their gills, smothers spawning beds and disrupts the ability of fish to relocate ancestral spawning grounds. Taken together, it took an estimated 50-100 years for caribou herds to become predictable food sources again, while fish likely took as little as a decade to return to healthy levels within the White River Ash East footprint.
Clinker and Obsidian
Pre-contact campsites in the north were often lived at for short periods of time and abandoned for long stretches. That makes it difficult for archaeologists to see the impact of an eruption. To remedy this, researchers looked at many sites across the north and measured the distances that people exchanged types of stone (one of the only raw materials that preserves in northern landscapes). Certain stone types, like glassy obsidian and bubble-filled clinker, were good for making stone tools and can be geochemically matched from an archaeological site back to its specific source (like a fingerprint at a crime scene matched to a known criminal). By comparing exchange patterns before and after the volcanic eruption, archaeologists build networks of contact that people maintained and relied on to weather environmental challenges.
Following the White River Ash East eruption, the movement of clinker shrinks. This suggests that people in NWT moved east from the ash footprint and shifted their focus away from long-distance contact to short-term survival among their caribou-hunting kin. In the Yukon, obsidian from the south becomes more common after the eruption. Archaeologists believe that people vacated parts of southern Yukon that were smothered by volcanic ash to live with coastal kin to the southwest. Many of them returned to their homeland up to a century later with a new type of exchange pattern that involved more southern obsidian.
Continental migration
Perhaps not everyone returned home after the eruption. Oral history tells a story of ranked societies of Dene people in southern Yukon. Noble classes gained power and prestige by controlling (monopolizing) key hunting and fishing sites and trade relationships with their coastal neighbours (Tlingit people). One theory is that lower classes, or a band of Dene migrants, who left the volcanic ash footprint decided not to return.
Where did they go and why? Archaeologists argue that, after the eruption, Dene groups may have found a place to thrive on the coasts of northwest British Columbia by helping to move goods through foreign hands and with other Dene neighbours. Small groups of Dene merchants may have continued a southward migration that lasted for several centuries.
Linguistic anthropologists (people who study languages) know that Dene-speakers migrated from somewhere in northwest Canada or Alaska to coastal British Columbia, Oregon, coastal California, the American Southwest and the Great Basin. Based on models of how quickly languages change, some of these linguistic splits happened at about the same time as the White River Ash East eruption (1,200 years ago).
Migration, ideas, and why it all matters
The continent-wide migration of people informs how ancestral groups found homes across North America over thousands of years. The movement of people also helps explain how religion, language, DNA, diseases, technologies and other ideas spread over millions of square kilometers. For example, Dene people who temporarily lived on the coast after the White River Ash East eruption are thought to have returned home with new bow and arrow technology and an interest in exchanging copper, both of which are visible in archaeological records.
Archaeologists have come up with several theories of Dene migration. Some believe that the Dene migrated through Alberta en route to the US with splinter groups that cut off west to the coasts of Oregon, Washington and California. Others argue they moved through interior British Columbia and then split to the coastal US and interior Southwest and Great Basin. Others argue that they moved down the coast and on to the interior of the US, with pockets of Dene people choosing to settle down along the way. Whichever path (or combination of paths) were taken, migrating people helped move ideas and goods. The Dene were not just refugees from the northern interior; they were conduits of cultural change wherever they chose to reside.
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