In case you didn’t know what Angel Mounds is, I will link you to the web site. In case you didn’t know what I’ve been doing lately, I’ve been digging at Angel Mounds, to which I link you to our Field School Blog, and you should go read it. Doo eet.
I’ve been here for a week now and we are just now opening units up. Let me explain why it’s taken this long, because it’s actually a really cool reason.
Grad Mentor Matt with the Magnetic Gradiometer, walking lines to get a picture of the ground beneath.
For the first week we checked and set up the equipment we were going to use. Aside from the usual shovels and screens we’re using a Magnetic Gradiometer (aka Magnetomer or Mag for short) this year on pretty much all of the site we’re working on. This awesome little device use two sensors to measure the gradient of the magnetic field in the ground. It then creates a picture from those readings that can fairly accurately show where features are going to be on the site. It can’t show us depth and iron or magnetic metals will create these huge spots in the picture, but otherwise the picture is incredibly helpful in planing where to dig.
Magnetic gradiometer map of Prehistoric fire-hearths (site unknown). Image from Wikipedia.
So, now we have our own image of the site ground showing us a very interesting image of the first terrace of Mound A. This allowed us to put in four 1 meter by 1 meter units on the terrace right where the cool stuff is.
Honestly, this saved us tons of guess work and wasted effort, and really it only took one day to get the area surveyed and the image processed. Granted we did have to prepare the area and make sure any modern metal was well away from the area to be surveyed, so two days at max, and we (by we I mean Matt) covered a 60 meter by 60 meter area in a couple of hours. That’s pretty good.
I really can’t explain how much time and man power this saved us, or really how awesome cool the picture is.
Learning how to sharpen our trowels into razor sharp objects.
But all that was done last week, which means that today we actually BROKE GROUND! (Que Fan-Fair and Confetti!)
We opened four 1 meter by 1 meter units on the first terrace of Mound A. All of them placed over places where the Mag showed us anomalies. Now, I am used to much bigger units, but I am also used to blindly digging based only on land forms and previous surveys. This is much better. Survey taken, spots identified, units opened, done.
Dr. Bill Monaghan from IU using the Total Station to locate and record points on the site grid on the terrace.
For those who don’t know, the first step here is setting up a grid. Which I am not going into this time. (Did I mention our Field School Blog and how you should go read it?) Once we’ve got that done and we have the Mag image, we picked out smaller areas for the units, which also had to be shot onto the grid using the Total Station (pictured above). If you’ve ever seen a survey crew on the side of the road, that’s the camera looking thing on a tripod they’re using. We use them to for the same reasons and then some. (again, go read the blog)
Once we have two points representing our North line recorded by the Total Station we set about laying in the other points using the age old method of tape measures and math.
Learning to lay in the other two corners of the unit via tape.
Once this is done the real fun begins, because now we can begin to dig. Which is much more then just sticking a shovel into the ground. See, we try and preserve the sod cap, or the grass on top. Usually because we plan to replace it afterwards. So because of that, there is a very specific way to remove the grass on top. (Also, we don’t want to screen the grass, because that takes forever and there is rarely anything useful in the grass.) What is this mysterious technique you ask? I call it, Sharpened Shovel Style!
See, we take square shovels (as opposed to spade shovels), sharpen them like knives, and then chop into the grass just far enough to get past the roots, but not really into the dirt much. Then we pry the grass up and roll it up and set it aside till we need it again. It sounds simple, but it can take a bit to get just right.
Popping the top off the unit. Note the perfect form…
Once that’s all gone we begin removing the dirt in arbitrary levels, unless the soil changes or we see a feature, and we begin taking copious amounts of notes. Seriously we take so much paperwork it makes the trees cry! But we have too, see excavation is destruction, and even with doing as little damage as we will be using the Mag image and all, we still need to record everything we do and find so that later we can reconstruct the events of the excavation via the paperwork.
Grad Mentor Erica teaching us how to fill out the paperwork.
We also tag every bucket of dirt that we plan to screen. Which bring me to the next new thing we’re doing here that I’ve not seen done on a CRM site yet. Water Screening! (I’m not saying it doesn’t happen, just that I haven’t seen it yet).
Filling out the tags that will go with the buckets of dirt to the water screens.
So, Water Screening is basically regular screening, where you take a bucket of dirt and sift it through a metal mesh screen stapled to a wooden box frame, and you add water. Lots of water, like from a hose. When you do a big dig, or a phase 3, you move a lot of dirt and to get though all of it, you usually have dedicated screeners that rotate with the diggers. You also have large screen tables so you can work on more than one bucket of dirt at a time, making sure it’s all from the same level.
Setting up the water screening tables.
Water screening works the same way except the screens are a much finer mesh and not metallic, and you get to play with the garden hose. Oh and mud, there is lots of mud.
And mud.
Playing with the hose.
The benefit of this versus dry screening is a near 100% recovery of anything that comes out of the unit. Also, you get to play in the water on really hot days.
So, that was pretty much what happened on day six of my field school here at Angel Mounds. All the hard work from last week payed off and now the new hard work of digging begins. Interesting features await us beneath the soil on Mound A, and we’re going to find them.
Waiting to dig.
“But wait Archy, where are you in all these cool pictures you just showed us?”
Where you ask?
Remember how I was telling you about the Magnetic Gradiometer? I was out there pulling tape so that Matt would know where he needed to walk in order to survey more of the area around Mound A. That’s right, there will be more units, and one of them has my name on it. (Seriously, I’m taking a Sharpie to it or something).
Me and my awesome hat, be jealous, it’s a Tilley.
