Friday, August 28, 2015

New Article: "Quantitative analysis of Munsell color data from archeological ceramics" Open Access!

My former student Lana Ruck and I have published an article on how to mathematically analyze Munsell color data. Although we use data from archaeological ceramics as our prime example, the method would work with any body of Munsell color data that was collected to address a hypothesis. The colors could be from soils, minerals, leaves, flowers, birds, and so forth, and the method would still work. We're so convinced that this article will be of wide interest that we paid for open access.

The idea is that you convert the Munsell readings to spatial coordinates in the Munsell color space and then perform spatial or statistical analyses on the coordinates, which are interval scale variables. For the kinds of hypotheses I wanted to test--whether the ceramic colors from one houselot or cluster of houselots were the same as those from another--I decided that logistic regression was probably the right technique because:
  • the dependent variable (the provenience, i.e., the houselot of cluster of houselots) was a categorical variable; and
  • the data were demonstrably non-normal, thus eliminating linear discriminant analysis.
I've been struggling with the issue of how to analyze this kind of data ever since I got back from Mayapan in 1992 or 1993 with thousands of Munsell observations and realized that I didn't know how to perform statistical tests on them. My best guess is that I finally figured out how to do it right, at least in theory, around 2006 or 2007, but it wasn't until a couple of years ago that Lana came along and mastered the logistic regression.

Apparently, the real lesson here is that if you think about something for 20 years, you just might figure out the answer, although I hasten to point out that during those 20 years I studied quantitative techniques pretty intensively.  I wasn't just sitting on the beach pondering the problem solely in thought; I was actually educating myself--howsoever unsystematically--about the general topic of mathematics in archaeology. Nevertheless, there is a push among university administrators to systematize and quantify scientists' goals and productivity. So, if I put down on my annual assignment that I'm going to study how to analyze Munsell colors, presumably I'm expected to produce the article in the year it's listed. If you take into account how long it took to devise the original research design, excavate the artifacts, and record the Munsell colors, this article has been in the works for 25 years! Should I submit a 25-year plan as part of my annual assignment? If I do, I can probably say anything I want because I'll almost certainly be dead in 25 years.

Here is the reference, linked to the article:

Ruck, Lana and Clifford T. Brown (2015). Quantitative analysis of Munsell color data from archeological ceramics. Journal of Archaeological Science: Reports 3:549-557. 

Just in case the link doesn't work for any reason, here is the URL: http://www.sciencedirect.com/science/article/pii/S2352409X15300730#

Enjoy!

As always, comments welcome.

Sunday, August 23, 2015

Soils of Latin American and the Caribbean

For those of you who, like me, sometimes work in areas of Latin America or the Caribbean where soil data are rare, difficult to obtain, unpublished, or simply unavailable, there is a very useful new work that I'm finding helpful: Atlas de suelos de América Latina y el Caribe.


It includes complete maps of the region, although they are published at a scale of 1:3,000,000 which can make identification of the location of individual sites difficult. Nonetheless, I have found it an extremely useful work. Not only are the maps helpful, but the soil taxonomy is explained with great simplicity and clarity, which is convenient for an archaeologist with no meaningful training in soil science.

Here is the citation suggested in the front matter of the document:

Gardi, C., Angelini, M., Barceló, S., Comerma, J., Cruz Gaistardo, C., Encina Rojas, A., Jones, A., Krasilnikov, P., Mendonça Santos Brefin, M.L., Montanarella, L., Muñiz Ugarte, O., Schad, P., Vara Rodríguez, M.I., Vargas, R. (eds), 2014. Atlas de suelos de América Latina y el Caribe, Comisión Europea - Oficina de Publicaciones de la Unión Europea, L-2995 Luxembourg.

Even better, it's available online at:  http://www.fao.org/agronoticias/agro-publicaciones/agro-publicacion-detalle/en/c/239323/

Cheers!
 

Thursday, July 23, 2015

The Elsevier Manuscript Submission System

So, I recently had to use the Elsevier Manuscript Submission System to change the corresponding author on an article that one of my former graduate students and I had submitted. What a nightmare! The system seems like it was designed by Nazi psychologists who got frustrated when the waterboarding took too long to work.

Even though I had previously filled out all their forms, and then consolidated my various journal profiles--a complex and confusing set of tasks--the system would not let me get to the dashboard or do anything until I had filled out several more screens full of additional information.

I was tempted to write to the editor and withdraw the submission, and I might have if doing so would not have caused problems for my colleague.

Am I the only one who hates it when people use their power to force you to do things you don't want to do? Might there be something just a tad unethical about doing that?

The information they were requiring had something to do with my research foci--I wasn't paying close attention because I was so annoyed. I don't remember what I filled out, but I do recall that I didn't do it carefully.

If they start asking me to peer-review articles on the sex lives of dung beetles, I guess that will be an indication of what I put down.

Do you find their system frustrating, or am I being oversensitive?


Rubén Darío ceramics

Posted for a friend...Click on photographs for larger images. More to come...

Exterior, body sherd, striation and roughening zoned with broad grooves.

Exterior, shoulder of jar, roughened with zoned excised geometric designs.

Exterior, shoulder of jar, detail of excised geometric design on previous sherd

Exterior, shoulder of jar, detail of excised geometric design on previous sherd

Exterior, body sherd, zoned striation

Example of paste

Example of paste

Example of paste

Exterior, body sherd, zoned striation in quatrefoil (?) cartouche

Exterior, body sherd, daub of red paint on polished surface

Example of paste

Polished black body sherds, exterior

Polished red body sherds, exterior



Exterior, body sherd, zoned roughened below; polished, white slipped and incised above. Zigzag resembles rocker stamping

Body sherd, exterior, pinched and impressed ridge in brushed or roughened band; no applique?

Exterior, modeled body sherds, eye? (left), nose and mouth (?), right

Red painted tecomate rim, exterior

Red painted tecomate rim, interior
Profile of tecomate rim
Body sherd exterior, polished above, roughened (scraped) below




Body sherd, exterior, polished above pinched-impressed band, roughened below, with excised geometric design



Body sherd, exterior, detail of roughened zone showing excised geometric design


Low, sharply everted, jar rim, neither burnished nor polished
Profile view of previous rim
Example of brown paste

Body sherd, exterior, polished above, excised below

More on the lahar

The "lahar" has been mapped as a lava flow, but it's so unconsolidated that I wonder whether it might not be pyroclastic, or at least of low viscosity. See Figure 1 in

Hazlett, Richard W. (1987). Geology of the San Cristobal Volcanic Complex, Nicaragua. Journal of Volcanology and Geothermal Research 33: 223-230.

I have heard rumors of an archaeological site on the south side of San Cristobal that has mounds partly buried under a lava flow. The edge of this flow would presumably be the best place to look for it. So, we went back to drive up the east side of the flow last Sunday. We saw some interesting stratigraphy in stream cuts, but no sites.

Oh, well. Maybe next time. I'm convinced that if you look around enough, and know what you're looking for, you'll eventually discover something interesting.


Saturday, July 11, 2015

The Crew and the Cosmapa Lahar

Here’s the problem.


The Cosmapa site is buried. In Shovel Test 8, the northeasternmost shovel test, the buried surface is particularly clear (Figure 1).

Figure 1. Sharp Contact between the sterile superposed volcanic sand and the underlying buried soil rich in artifacts in Shovel Test 8, Cosmapa
The buried soil appears at about 100 cm. The first sherd appeared at 102 cm. The contact between the overlying ash or sand and the clayier buried soil is particularly sharp. Last year, while writing the informe, I noticed on Google Earth that there was what looked like a large lava flow that came down the southern flank of San Cristóbal straight toward Cosmapa and stopped just south of the Highway, about 1000 m north of the site (Figure 2).

Figure 2. Lava Flow or lahar? In Yellow. Site is in blue.


A couple of days ago, I was looking at it again in Google Earth, and I came down to ground level and "flew" toward San Cristóbal, and I saw that the “lava flow” looked like a gigantic lahar that came straight from a fissure in the cone of San Cristóbal, where the collapse looked quite sharp and fresh (Figures 3-6).


Figure 3. At the summit, it looks like a lahar. Notice the sharp fissure where part of the cone has given way and a giant avalanche has cascaded downward.

Figure 4. The collapse feature is clearer from an angle in this Google Earth image. See how fresh it looks.

Figure 5. Here you can see the relation between the flow and the lahar above. They are almost, but not quite, aligned.
Figure 6. Same as the previous map, but zoomed in a little.

So, was it a lahar or a lava flow? We drove out to look. It’s only 7.2 km from the rotunda at the entrance to Chinandega. We parked at the north entrance to the Cosmapa road. From there, you can see that the road is humped up where it crosses over the flow, whatever it is. We walked along the highway and looked at the section visible in the drainage ditch. We got to a bridge and went down into the dry streambed. There we could see what looked like a lahar deposit in the lowest stratum with ash deposits sitting unconformably atop it. The lahar deposit had lots of sharp stones (not rounded river stones) all mixed in it and lightly cemented, but I could pry bits off with my trowel. We went back to the car and drove east to a dirt road that runs north just shy of the stream. Then we drove north along the road, which follows the eastern edge of the flow. The flow is pitted with big quarries, which makes sense: the volcanoes must be the only places to get stone in the coastal plain. And this recent flow, whatever it is, is clearly recent—there’s only stunted vegetation growing on it, as you can see on Google Earth—so the stone must be easily accessible. In the quarries and road cuts along this track, we could see that the flow is composed of a jumbled mix of totally unsorted, rough, angular, volcanic stone. The particle size varies from silt to house-sized rock, all tumbled together in piles and ridges (Figure 7).  Although there is some scoria mixed in, it looks to me like a lahar. I drove up the Posoltega lahar in 2000, only two years after it happened, and I have seen ancient, consolidated lahar deposits at Cusirisna in Boaco. They pretty much look like this one on San Cristobal (Figure 8), allowing for differences in parent material and age.

Figure 7. Lahar deposits in a quarry face
Figure 8. Ancient lahar deposit from the Las Lajas Crater near Cusirisna, Boaco, Nicaragua.

So, I think it is a lahar. It doesn’t look a lava flow. It’s largely unconsolidated.

If it's a lahar, it's huge. Look at it at the same scale as the Posoltega lahar, which killed a couple of thousand people in few minutes during Hurricane Mitch in 1998 (Figures 9 and 10). The two images are at the same scale.

Figure 9. Posoltega Lahar, from 1998
Figure 10. San Cristobal Lahar at the Same Scale as the Posoltega Lahar

Here's the crew. They're great (Figure 11).
Figure 11. Kelsey, Grazia, and Ashley, with Agateyte smoking pacifically in the background


Sunday, May 24, 2015

You may have been in the field too long if...

1) you've been listening to the BBC on the short wave for so long that you recognize the voices of all the news readers and can tell if they have a cold;

2) you stopped taking your malaria meds so long ago you can't remember the dosage;

3) you file your nails with the same bastard file you use to sharpen your trowel and your machete;

4) Sunscreen? Ha, ha, ha, ha, ha, cough, snort. Oh, that? That's just a mole;

5) You intuitively recognize whether the GPS coordinates are correct in DMS, decimal degrees, and UTMs;

6) You can spot a sherd on the side of a dirt road while driving by at 50 kph;

7)  You're on a first-name basis with every farmer and hunter in the district/state/department/canton/province;

8) Your athletic socks have evolved to the point that they could pass a Turing test;

9) trenchfoot is a frequent topic of casual discussion;

10) you don't even think about TV any more; and, drum roll please,

11) you've forgotten what it's like not to have diarrhea.

.


Saturday, May 23, 2015

Kelsey Willis, Undergraduate Researcher Guest Blogger




Reporting from Chinandega, Nicaragua:

I am here with my advisor, Dr. Clifford Brown, and one of his graduate students, Ashley Gravlin, to analyze archaeological ceramics. The ceramics are from over 20 sites that Dr. Brown found in his previous fieldwork. We want to analyze the collected ceramics so we can define the people who created them. For our goal, we believe the best way to come to such a conclusion is to classify the ceramics into types, varieties and groups. To classify the ceramics we will be observing the finishes, decorations, colors and forms of the pottery; recording the coarseness by examining the temper particle size, shape and type; and measuring the colors of the ceramic’s paste, slip or paint (if included).

One of the first things I thought would be really amazing to see is where some of the ceramic material came from, so a few days ago, we headed out to some sites. We went to the sites known as Cosmapa Oriental, Santa Cristina, and Rio Chiquito in that order. At Cosmapa Oriental, which is a large peanut field, we walked in our own straight lines and found sherds just lying on the surface. A few of the sherds we found resembled a ceramic type known as Las Vegas polychrome (Figure 1) and we photographed them. We also came across a biface stone tool fragment that was made of chert (Figure 2).


Figure 1. Potsherd of Las Vegas Polychrome from the Cosmapa Oriental Site
Figure 2. Chert biface fragment from the Cosmapa Oriental Site


At Santa Cristina we did not find as much, but we did come across a large painted ceramic support. After spending a little more time there, we headed to Rio Chiquito. In this area, the ground was covered in grass and weeds. It took my eyes a while to adjust to finding geometric shapes on the ground, but once they did I saw sherds every five steps. We even found some obsidian shatter and one obsidian flake.

We didn't collect any artifacts, but it was really exciting and an awesome experience to visit actual archaeological sites!