Field Work Techniques : Deciding Where And How To Dig

Once a good archeological site is found, the archaeological team is on a race against time. Sun, insects, wind, and rain can quickly destroy anything that's unearthed and exposed, putting a pressure on the team to extract as quickly as possible. On the other hand, to avoid damaging items removed from the ground, you have to proceed gingerly and carefully. Extracting artifacts from an archeological site is best described as trying to do the work of a backhoe with a garden trowel.

Before any artifacts are removed, a lot of documentation is done of the initial conditions of the site – what the talus and till looks like, and making guesses about what the site was used for, whether a camp site, a cemetery or village, or something else. After that, the key is taking lots of photographs – knowing how the artifacts are positioned relative to the existing landscape is critical information for setting search patterns for other artifacts. Details gathered include grid coordinates, and a detailed local topological map, usually made with stadia rods and transits.

Artifacts are then noted as to where on the site they've been found. Buried archaeological features are usually "examined" long before they're dug up, using special instruments like the proton magnetometer, which will detect variations in the local magnetic field from things like buried iron artifacts, or fired clay artifacts, or pits that have been dug and refilled (all soil has small amounts of iron in it; variations in this amount show up as minute variations in the magnetic field; disturbing the soil can create variations in the magnetic field as well.)

In some ways, being an archaeologist doing field work can be likened to an episode of CSI, except that it's seldom going to be finished on one nights showing!

If something needs to be excavated, it's done with great care and trepidation. Every time you dig on an archaeological site, you lose information. Things are disturbed, items are broken or buried, or have their position shifted. Before excavation beings, that grid coordinate is laid down with ropes and stakes, and it's all recorded on a site plan for posterity.

Excavation is slow work. Every spade full of material is examined for artifacts or the broken remnants of artifacts, usually by sifting it onto a plate and running a brush over it, or running it through a wire mesh sifter, usually with 1/4" gratings, but sometimes smaller than 1/16th of an inch – this makes it easy to find stone flakes, shards of pottery and bone fragment, which would otherwise be discarded.

If a burial site is being exhumed, bones are drawn in their orientation (or photographed) before they're moved – it's very easy for bones to crumble to dust when exposed to air or moved. At the end of the work day, the archaeologists usually cover the site up with tarpaulins to keep breezes from damaging their work, and it's not unusual (particularly in Biblical archaeology) to use earth movers to re-bury a site and plant grass on it at the end of the digging season.

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