Throughout my archaeological career one aspect of site recording and report writing always seems to trip everyone up – deposition and depositional context. I think it can be a scary topic because not much time is spent learning about it and it can seem daunting. However, for those of us who practice archaeology for a living, we know how crucial it is to correctly identify the on-site depositional processes and understand how those processes relate to the site’s potential for subsurface cultural deposits.
I know I can create a PowerPoint and lecture my students till the cows come home (which is weird, since I’ve never seen cows leave or come home – but that’s neither here nor there), or I can take it a step further and show them how deposition occurs.
- Bag of sand
- Plastic tub or bin (Photo 1)
- Artifacts & Features (Photo 2)
- We just bought some small rocks, plastic toys, stickers, and a wooden bird house. You can choose whatever floats your boat.
- Squirt bottle
- Watering can
- Wide flat plastic object
- We used a plastic folding cutting board
- Hand fan or any type of air-moving device
This activity has been divided up into four units – with each unit representing a different landform, and their respective depositional contexts.
- Unit 1: Dune landform being affected by aeolian processes.
- Unit 2: An alluvial fan in a valley being affected by alluvial processes.
- Unit 3: A ridge landform being affected by alluvial, colluvial, and residual processes.
- Unit 4: Cliff landform being affected by alluvial/wave action processes.
Pour the sand into the plastic tub, make sure it’s at least 1/3 the way full (Photo 3)
Once the tub is filled with sand, push the sand to one side to create a dune. We chose to have buried objects within the dune as well as exposed objects outside of the dune (Photo 4). We then used the hand fan to blow the dirt around – mimicking aeolian processes which would affect this landform and the artifacts and features within it (Photo 5). As you can see the black rock feature and the bones are now more visible, while the rock ring is now partially buried. This exercise demonstrates that sand dunes make for an unstable environment, and that there is high potential for subsurface cultural deposits within them.
To set up for this lab, all you have to do is use your finger to create a water channel through the dirt (Photo 6). Next you’ll need a full watering can and the funnel. Starting at the top of the alluvial fan, begin to pour water into the funnel and get the channel flowing. Alluvial processes will widen the channel, unearth additional buried objects, and soil will accumulate on/and around the rock ring feature (Photo 7). This exercise demonstrates that alluvial fan environments can be unstable/stable – depending on the sites proximity to the water source, and also highlights the potential for subsurface cultural deposits.
To set up for this lab, you’ll want to create a faux mountain or ridge feature on one end of the tub – it’s ok to leave the rock ring as it is. We buried objects within the ridge and then put a “historic cabin” on top of the ridge (Photo 8). You’ll need a squirt bottle filled with water and possibly the watering can. Starting with the squirt bottle, begin spraying the ridge with water. Dirt will fall down the slope, mimicking colluvial and alluvial processes. If you want a more dramatic effect, use the watering can as well. This exercise demonstrates how erosional processes can wear down large landforms over time, which effects features atop them, and potentially exposes artifacts and features within them (Photo 9).
To set up for this last lab, you want to mash all the dirt into a faux cliff, and then fill the remaining space in the tub up with water so as to mimic a coastline. We chose to bury some artifacts and features within the cliff, we put the “historic cabin” on top, and placed several artifacts along the waters edge/beach (Photo 10). You’ll need that wide flat plastic object for this part – we chose to use a folding cutting board, this object will be used to create waves. The exercise demonstrates how repetitive alluvial erosional processes (i.e., waves), can affect the adjacent landform. Erosion initially removed artifacts from the beach, and then slowly began exposing artifacts and features within the cliff. Eventually the entire landform is worn away and the house atop it falls (Photo 11).
This lab is designed to get your brain parts thinking about the landform and landscape in which you are working, how the associated soils got there, and how those soils have affected, and are affecting your archaeological site. We as archaeologists need to evaluate how stable the environment is, and to determine the potential (if any) for subsurface artifacts or features at a given site. At the very least, it was probably fun to slosh dirt, water and mud around in a big plastic bin right?
If you have done another deposition activity or have ideas for a new activity, I’d love to hear about them! Comment below or shoot me an email at firstname.lastname@example.org. Cheers!