Fingerprints in Glass: Obsidian and Ancient Human Relationships

Written by: Todd Kristensen, Archaeological Survey of Alberta

A butchered bison leaves bones behind; a fur trade post leaves rotting walls for archaeologists to discover. But humans are more than what we eat and build. To many, our lives are defined by relationships to other people. How do archaeologists in Alberta uncover and reconstruct human relations from 10,000 years ago when not much preserves in the soil?

Archaeologists use microscopic clues to link stone artifacts back to the quarries where the rock originated; this “provenance” work can reveal ancient networks. In a blend of geochemistry and sociology, researchers use volcanic rocks in particular to understand how groups interacted and moved across landscapes for millennia.

Obsidian arrowhead found in the Grande Prairie area of northwest Alberta. Source: Todd Kristensen.

Obsidian and Trace Elements

Obsidian is a volcanic stone born of magma that cools so quickly upon exposure to air that it lacks any crystal structure. This ‘amorphous’ rock is perfect for making stone tools. The edges are sharp and the material has an attractive shine or lustre; it has style and function. And importantly, when obsidian is a liquid bubbling to the surface, it absorbs microscopic elements from its volcanic chamber. Like scars from an igneous fight, these elements make each source of obsidian unique and recognizable to archaeologists.

Obsidian formation from underground magma to surface lava and on to a glassy rock. Source: Todd Kristensen.

The end result of this process is a rock highly valued for making stone tools, and of high interpretive value to archaeologists who can connect every obsidian artifact at a site back to its volcanic origin. 

Images of obsidian in thin section show the flowing lines of movement as the lava quickly cooled. Source: Todd Kristensen.

Connect the Dots

Alberta is an ideal place to study obsidian artifacts. The province lacks any natural sources, so any obsidian found at a site had to be transported from beyond our borders. We have volcanic sources to the west in British Columbia, south in the United States, and northwest in the Yukon and Alaska. By drawing lines from archaeological sites to sources, archaeologists can unravel mysteries of human relationships.

Map of all volcanic sources of obsidian that show up as artifacts in Alberta. Source: Todd Kristensen.

Fingerprints and Obsidian Stories

In 2014, a research team began compiling information about sourced obsidian in Alberta. Since then, a database of over 1,000 artifacts is beginning to shed light on human networks. The earliest obsidian artifacts, whether in northwest Alberta or on the Plains in the south, comes from American volcanoes. If people colonized what is now Alberta from the north, we would expect the earliest obsidian to come from Yukon or northwest British Columbia, which is not the case. The results suggest that the earliest human occupants arrived from the south and maintained social connections with groups in the vicinity of volcanoes in Oregon, Idaho and Wyoming.

Obsidian artifacts from some of the early phases of human occupation in Alberta. Source: Todd Kristensen.

Maps of obsidian occurrences are also revealing contact zones between different people. The four most common obsidians in Alberta are from Bear Gulch (Idaho), Obsidian Cliffs (Wyoming), Edziza (northwest BC) and Anahim (west central BC). Edziza obsidian outcrops in the heart of Indigenous people called Dene, who historically occupied the forested regions of northern Canada. On the other end, Obsidian Cliffs and Bear Gulch obsidian is within the sphere of influence of Plains people like the Blackfoot. By mapping the extent of each obsidian, archaeologists can track movement and contact zones (or avoidance zones) of different groups of people.

Map of sourced obsidian artifacts in Alberta. Source: Todd Kristensen.

The obsidian studies have also detected some unusual occurrences. For example, the projectile point below was reportedly found around the 1920-40s by a rancher in the Trochu area of central Alberta. When it was first noted by researchers in a sealed glass frame at a local museum, the point was assumed to be a modern reproduction or fake. Obsidian sourcing revealed that the decorative weapon tip matches geochemistries of both Edziza in BC and Pachuca obsidian in Mexico. Work is ongoing to determine if this point was purchased at a market in Mexico over 50 years ago or if it indeed originates in BC and was placed at an archaeological site in the province several thousand years ago.

Obsidian sourcing studies are helping to determine if artifacts in local museum and collections are legitimate or modern reproductions. Source: Todd Kristensen.

Obsidian, Relationships, and the Heritage Art Series

Archaeologists are continuing to untangle relationships in the deep past. Provenance studies demonstrate that even small fragments of stone at archaeological sites have interpretive value. New techniques and laboratory discoveries are constantly helping to unlock the potential of Alberta’s historical resources.  

Pictured below is an acrylic and charcoal study of an obsidian artifact by Edmonton-area artist Tom Saunders that captures the lustre and beauty of a raw material valued by people for over 10,000 years. This artifact was found in 1937 just east of Edmonton and was recently matched to obsidian from Mount Edziza, almost 1,800 km away in BC. The Heritage Art Series is a shared project of the Historic Resources Management Branch, the University of Alberta and the Royal Alberta Museum: each artwork tells an important story about the people of our province. We hope it fosters a greater awareness of our past and instils a deeper respect for it.

Acrylic and charcoal study of an obsidian. Source: Tom Saunders.

More stories and colourful scenes from Alberta’s past from farms and fossils to mountains and oil sands, can be viewed here.

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