Week 2: Excavation commences!
Finally after a week of lecture and field trips, the students were allowed to break ground on two excavation trenches. Excavation is performed either with trowels, shovels, or a combination of both. For teaching purposes, trowels are the better way to go to begin with. This way students can get a feel for how the actual process (and sometimes tedium) of excavation works. By troweling, each rock, wood fragment, glass shard and iron nail can be identified by both feel and sound. Over time, excavators may become just as delicate with a shovel as with a trowel but for now, slow and steady is the way to go.
Early on in an excavation there is often more standing around discussing what to do next than actually physical work. Decisions must be made regarding what to ignore, what to keep (artifacts-wise), and how best to document the vertical process of removing earth from a uniform trench. Some crews like to say every 5 or 10 cm is a new level. This means that any artifacts found within that level, regardless of the sediment/soil’s composition, are grouped together in the same context. This is preferable when dealing with uniform sediments and contours, but in the Keweenaw, where rocks, deposited both naturally and by humans exists side by side, this is pretty difficult. For our excavations, we choose to group levels by their sediment/soil context. The topsoil is a surface level for instance, while a stamp sand deposit just under it is another level (level 1). Digging continues until a new composition is unearthed. Maybe its a deposit of clay. Perhaps a wood floor or an ash stain marking an old camp fire. you may just even hit bedrock, which is usually the endpoint of any excavations.
We know from background research that our levels should be comprised of topsoil, followed by stamp sands deposited as fill during the late 19th century after principal mining at the Cliff ended and small-scale tribute work began using a smaller stamp mill that sat atop the original (look forward to a future post on the many phases of stamp mills at the Cliff site). Under that stamp sand deposit, it was hoped to find either a working floor of wood or stone. Maybe some wood machine mounts, and probably some iron bolts and even artifacts like screens and stamp shoes. As we excavate, we take soil samples using a long probe which allows us to know what to expect in the next 20 cm or so going forward.
To begin, we opened two trench units, SM100.T1 and SM101.T3. 100.T1 is at a higher elevation than 101.T3 and this can be seen in the photo at left. Remember, a stamp mill uses gravity to accomplish its work, and as excavation continues this will (hopefully) become more apparent.
In the coming days you will have the opportunity to see if our presumptions were correct. I can tell you there were definitely some surprises.