Tag Archives: obsidian

Life from Ash and Ice: A documentary film about Mt. Edziza

Screenshot of Knowledge Network video about Mt. Edziza.

Screenshot of Knowledge Network video about Mt. Edziza. Click to go to site.

For various reasons I’ve been off work for a while and that has meant being off blogging as well. If you’ve commented on posts recently then thanks; if you’ve emailed my gmail account and still would like a reply then maybe try again.

Anyway, what better way to resume making the occasional post here than a film about the place where I did some of my first ever fieldwork: assessing the then-proposed Site Z dam site on the Stikine River in Tahltan territory, far Northwestern British Columbia, in the shadow of Mt. Edziza.  Edziza is well known to Northwest Archaeologists as one of the region’s most important sources of obsidian, a volcanic glass highly suitable for making certain kinds of stone tools.

The video, Edziza: Life from Ash and Ice, can be watched in full on the B.C. Knowledge Network’s web site.  (NB: I had to change the resolution from a default of “lousy”).  Obviously the geology of the Edziza Complex is pretty cool (and is covered in the first half of the video, which features John Clague among others), but there’s quite a bit of more direct archaeological interest in the second half.

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Northwest Research Obsidian Studies Lab

A flake of obsidian from DhRr-18, southern British Columbia. This visually-distinctive glass is from the Mount Garibaldi obsidian source.

Obsidian is a kind of volcanic glass and was highly prized for making certain kinds of stone tools.  Obsidian forms at places of relatively small outflows of magma, or liquid rock.  Small flows can cool quickly, which allows the formation of a glassy crystalline structure ideal for stone tool manufacture.  Small flows also represent a small sample of well-mixed magma, and thus each little patch of obsidian may share a very distinctive chemical signature.  This signature, usually identified by trace elements such as Strontium, Zirconium, Yttrium and Rubidium, then allows for the chemical fingerprinting of each source.  Any obsidian artifact found, whether at a source or not, can also be “fingerprinted” and then compared to a catalogue of known obsidian ources.  Since the artifacts don’t move around on their own but only through the agency of humans, the distribution of obsidian artifacts is a proxy measure for the movement and interaction of people.  When you have hundreds or thousands of such artifacts and a large database of known sources, then you can start to see large scale, long-term social interaction emerge from the silent archaeological record.  Most obsidian isn’t visually distinctive enough to sort out by eye alone, so these geochemical methods are essential.

So far, so Archaeology 101.  I was really happy to find that Oregon’s Northwest Research Obsidian Studies Laboratory has a web site not which not only solicits business, but is a highly educational and informative site about many aspects of obsidian analysis, with a focus on the Northwest. Continue reading