Archaeology Corner: Excavating 101

class="MsoNormal">Today was my first day of excavating (yay!) so I thought I’d tell you a bit about what that entails. Warning: as the title implies, this whole thing is a bit educational so skip to the pictures if you don’t want to know the nitty-gritty of playing Indiana Jones.

Look, a grid!

We start by laying a grid using string. If you ever wondered in Geometry about real practical applications for the Pythagorean Theorem, here’s one! Of course, since I had been laying grids all last week with GPR I’m pretty great on those by now.

As soon as you have your unit in place you set a Datum. This is your reference point from which you take all measurements. They’re usually in the southwest corner of a unit but that’s only a convention and can change based on convenience. The site I was digging at today, for example, had a datum in the northwest corner. In addition to having a datum for each unit there is also a master datum for the whole site, which everything can be calculated back to. The survey team locates every datum precisely so that the entire site can be mapped through the measurements we take from them.

Next we take the elevations of the four corners and the center of the unit using a line level. This is really helpful in two ways. First, it gives a sense of the unit’s topography for our notes and posterity, and second, it helps us keep track of how far we’ve dug.

Since we are working in the jungle, there is then a ton of organic debris (leaves, etc) that we need to move even to get to the dirt. From there we take careful notes on the “matrix,” or the soil composition, color, density, etc. There are actually these nifty books called Munsell books (no clue if I spelled that right) that serve as the authoritative dictionaries of soil color and we use them to define the exact coloring. This is all important because any change in matrix is a possible cultural feature. For example, we found a platform in our unit that is only recognizable because of a slight increase in density and clay content.

Then you get to actually move some dirt! Using the flat sides of our trowels and brushes we remove the soil (and rocks, sometimes) in ten-centimeter layers. This layer depth is arbitrary but it’s a good starting point if you don’t know what you’re looking at. If you hit something interesting, layer depths are free to change. We scrape the excess dirt into dustpans (who knew?) then dump those into buckets and, when the buckets are full, put the dirt through sifters to make sure we don’t miss anything. Its thorough, slow work, but SO rewarding when you start finding things!