The NRCS Web Soil Survey

A couple years ago, this blog published a post about geology and shovel testing. The purpose of that post was to explain what every field technician should know about geology and soil science while shovel testing during an archaeological survey. If you haven’t read that post, I would recommend reading it here; otherwise this new post will be difficult to follow. My academic sources are listed at the end of that blog post, in case you would like to do additional reading.

To briefly summarize my original post, I explained that soils can either be residual or depositional. Residual soils have formed in situ from weathered bedrock. The horizons that you see in the profile of a residual soil are not chronological layers of sediment; they formed within the existing geological material due to biological and chemical processes. Artifacts left on the surface of residual soil are often buried, but not by the deposition of new sediment. They are buried by bioturbation and incorporated into the A horizon (topsoil). Meanwhile, depositional soils have been transported from their original location and deposited elsewhere as sediment. Soil can be transported by wind, water, glaciers, and gravity. Archaeological sites found in depositional environments, such as floodplains, have the potential to be deeply buried, or possibly stratified by time period.

What I didn’t address in my original post is that it can sometimes be tricky for field techs to determine how the soil beneath their feet was formed or transported, even if they have a good academic understanding of geomorphology. It’s not always easy to tell how old a landform is or how it came to be.

For example, it’s essential for archaeologists to be able to distinguish floodplains from upland landforms, because floodplains have the potential to contain deeply buried sites. In some places, the upland areas grade so imperceptibly into the floodplains that it’s very difficult to notice the elevation change at all, and the upland landforms are sometimes almost as perfectly flat as the floodplains, because they formed from some kind of alluvial activity sometime in the deep past. In the Sam Houston National Forest in east Texas, many of the “upland” areas belong to the Lissie Formation, which formed from fluviomarine sediment during the middle Pleistocene. The Lissie Formation is extremely flat because it is basically a series of deltas that formed along the coast when the sea level was much higher than it is today, during one of the Pleistocene interglacial periods (during the Pleistocene, the climate was generally cooler than it is today, which would cause sea levels to drop, but there were interglacial periods during which the climate was hotter, the sea was higher, and the coastal deltas formed at a higher elevation than they could today). So the Lissie Formation consists of a flat, ancient terrace that no longer accumulates any sediment (and has not done so since the middle Pleistocene). But the bayous flowing through the Lissie Formation are depositing Holocene alluvial sediment along their banks, and often, this alluvial sediment is barely any lower than the upland terrain. While walking through this national forest, sometimes the only way that I can distinguish the upland areas from the Holocene floodplains is that the floodplains have standing water and the upland areas have slightly less standing water.

My point is, understanding the history and formation of a landform can be difficult. There’s an entire academic discipline, known as geomorphology, which is devoted to this endeavor. I don’t think it’s necessary for every archaeologist to formally study geomorphology. But I do think archaeologists should be willing and able to use and (at least partially) understand the data that have been collected by real geomorphologists and soil scientists who have dedicated their careers to understanding the earth.

Luckily, soil scientists have made this fairly easy for us, at least in the United States, thanks to the United States Department of Agriculture Natural Resources Conservation Service (USDA NRCS). And that brings us to the topic of this post—the NRCS Web Soil Survey.

The NRCS is a federal agency dedicated to the study and conservation of soil, particularly in the interest of sustainable agriculture. Soil scientists employed by the NRCS have surveyed most of the land within the contiguous 48 states, classifying the soil into hundreds of different “series” and documenting the vertical profiles of each series. A “soil series” is a taxonomic unit consisting of soils that have been grouped together due to similarities in their formation, chemistry, and physical properties, such as color, texture, structure, pH, consistence, and mineral and chemical composition. The information collected by the NRCS is mainly intended to help farmers, but it is a valuable asset for archaeologists as well.

Archaeologists usually refer to NRCS data in their reports, but almost always in a very superficial way that doesn’t explain why the information actually matters. We list off the different soil series that have been mapped in our project areas and tuck that information into the front matter of our reports, along with other background information about the environment or geology. We seldom give the soil data any context, and I suspect this is because most report authors don’t really understand how to interpret the data in a way that is meaningful for archaeologists. We’ll say something like, “The soils within this project include Houston Black clay, 0 to 1 percent slopes; and Eddy gravelly loam, 3 to 5 percent slopes”—but what does that even mean? Why is it relevant for archaeology, and why bother putting it in a report?

Whether most report authors realize it or not, this information is extremely relevant. So let’s take a look at the soil data that have been published by the NRCS Web Soil Survey, which is free and open to the public. It can be accessed here.

If you open the website and navigate to the map page, you can zoom in to your project area on the map, then select your AOI (Area of Interest). After creating (or uploading) your AOI, you can click on the Soils Map tab, and you will see all the different soil units mapped out. Each soil unit will be labeled with some kind of code (Map Unit Symbol), and on the left side of the screen, that code will be paired with its corresponding soil type (Map Unit Name). It should look something kind of like this:

 

Figure 1: Screenshot of NRCS webpage

The Map Unit Name will include the soil series, the texture of the soil, the slope, and sometimes some other relevant information, such as how frequently the soil floods. One example would be “Houston Black clay, 0 to 1 percent slopes.” “Houston Black” is the soil series. “Clay” is the texture. Slope can vary within most soil series, so the soil scientists divide up each series into multiple units based on the slopes in each area.

If you can determine the soil series within your project area, that can usually tell you the age and/or formation of the soil—and that can tell you how deep you need to dig your shovel test, or whether there is any potential for stratified or deeply buried archaeological sites. The NRCS has another website with information about each soil series. That website can be accessed here.

If you look up the page for the Houston Black series, the very first sentence tells you how Houston Black soil formed: “in clayey residuum derived from calcareous mudstone of Cretaceous Age.” In other words, Houston Black is a residual soil that formed in situ from weathered bedrock. In this case, that bedrock is mudstone. Basically, the mudstone weathered into dark clay over time. That clay was not deposited from elsewhere (the sediment that initially formed the mudstone was transported from elsewhere, but that happened over 65 million years ago). This means, if you are shovel testing or excavating in soil that has been mapped as Houston Black, you can expect all the artifacts to be located on the surface or in the topsoil. There is little to no possibility for deeply buried artifacts, because artifacts would have been buried by bioturbation, not by the introduction of new sediment. There can still be quite a high possibility for buried artifacts if there’s a lot of vegetation, but those artifacts won’t be deeply buried. I would expect to find them in the top 20 cm.

 

Figure 2: NRCS webpage for Houston Black series

On the other hand, if your project area is located in an alluvial environment, there is a very real possibility for deeply buried artifacts. But not all alluvium is the same age, and artifacts are not likely to be deeply buried in ancient alluvium, because there has not been any deposition during the era of human occupation. If you look up the “Kian” soil series, you will see that it consists of Holocene alluvium, meaning that it consists of sediment that has been deposited in the past 11,700 years or so, and possibly continues to accumulate sediment today. But if you look up the “Burleson” series, you will find that this series consists of Pleistocene alluvium. Burleson soil can be found on upland terraces that used to be floodplains during the Ice Age, but as the rivers cut deeper and shifted course, these old floodplains stopped flooding, and new floodplains formed below them during the Holocene. Understanding the difference is key. Some archaeologists assume that all alluvium is recent in origin, but that simply isn’t true. There are still alluvial landforms left over from the Pliocene and Pleistocene, but they do not experience any deposition today.

I don’t think it’s impossible to find a deeply buried site on a Pleistocene alluvial terrace, but the site would have to be very old—as in, pre-Clovis old. I don’t think you should have to shovel test deeply into a Pleistocene terrace during a CRM survey simply out of the unlikely chance you might hit a pre-Clovis site (I certainly don’t want to, but maybe that’s out of laziness). On the other hand, you won’t find anything like that if you don’t look.

Often, the NRCS webpage for any soil series will explain that soil’s origin in the first sentence, but if it doesn’t, just scroll down to the “Geographic Setting:” section. This will tell you the “parent material” of the soil, and that will help you understand when and how the soil formed.

To help you visualize this a little better, I’m going to show you the downloaded soil data for a hypothetical survey area in Collin County, Texas. Below, you can see the satellite imagery of the project area—a patchwork of farmland and pasture between the towns of Melissa and Blue Ridge:

 

Figure 3: Satellite imagery of Area of Interest (AOI) in Collin County, TX

Now, let’s take a look at the soil units within the AOI:

 

Figure 4: NRCS Soil Units mapped within AOI in Collin County, TX

I don’t have them labeled because there are too many units, but these units are a combination of the following soil series: Altoga, Austin, Leson, Eddy, Ferris, Heiden, Houston Black, Stephen, Burleson, Lewisville, Wilson, Frio, Tinn, and Trinity.

Austin, Leson, Eddy, Ferris, Heiden, Houston Black, and Stephen soils are residual soils derived from bedrock that weathered in place. They formed from a variety of shales, mudstones, limestones, and chalks, most of which are probably Cretaceous in age, at least in this location.

Burleson, Lewisville, and Wilson soils consist of ancient alluvium. The NRCS explicitly describes Burleson and Wilson soils as being of Pleistocene age. The NRCS does not say during which epoch the Lewisville series was deposited, only that it is “ancient,” so it is probably Pleistocene as well. The Altoga soil series is a little trickier to place, because the NRCS does not say whether it is modern or ancient. What the NRCS does say is that "these gently to strongly sloping soils are on risers on stream terraces." Stream terraces are generally older than the current floodplains beneath them; often they used to be floodplains themselves, but now no longer accumulate sediment. If the Altoga series has formed on stream terraces, this likely means that the parent material is of significant age. So I have classified the Altoga series as "ancient alluvium" here, with the caveat that there may be some Holocene deposition.

Frio, Tinn, and Trinity soils consist of Holocene alluvium. These are places where you might expect to find deeply buried sites. The NRCS does not explicitly say that these series are Holocene in origin, but the Map Unit Name will often say something like “occasionally flooded” or “frequently flooded” after the soil series name. If these soils are still flooding, they are still accumulating new sediment. And we live in the Holocene, so this is obviously Holocene sediment. The NRCS doesn’t have to explicitly say that this is Holocene alluvium, you just have to use your common sense.

The map of all the soil units within the project area probably wouldn’t convey a lot of information to most people, even if I did label it. But a lot of report authors will add a soil map like that without any additional context.

Hopefully, this map will make the picture clearer:

 

Figure 5: Map of Soil Units within AOI in Collin County, TX, classified by soil formation and history

Figure 6: Legend

In the above map, I’ve classified each soil unit in the project area according to its formation. The soils here consist of residual soils, ancient alluvium, Holocene alluvium, and standing water. The gray units consist of residual soils. The light brown units represent ancient alluvial terraces, now heavily weathered and eroded. The red units represent floodplains consisting of Holocene alluvium. It might be difficult to tell from the map, but the residual soils are found on the upland areas. The Holocene floodplains are located along existing creeks. And the ancient alluvial terraces are generally located roughly alongside the current floodplains.

If you’re a field tech who just wants to know how deep to dig a shovel test, this map should make it fairly simple. In the residual soils, just dig until you reach the B horizon. Or until you hit bedrock, whichever comes first. On the ancient alluvial terraces, it should also be safe to terminate your test at the B horizon, unless you’re dead-set on finding a pre-Clovis site (honestly, I think it could happen). On the Holocene floodplains, just dig as deep as you can with a shovel.

That’s one kind of landscape you might have to survey, especially if you work in north Texas. But North America has a diverse array of landscapes, so I wanted to show another example, containing soils with very different formations and histories.

Below, you can see a satellite image of some farmland in Peoria County, Illinois, not far from where I grew up.

 

Figure 7: Satellite imagery of AOI in Peoria County, IL

And here is an unlabeled map of the soil units within that area: 

Figure 8: Map of Soil Units within AOI in Peoria County, IL

The soils within this AOI include the Rushville, Keomah, Sylvan, Dodge, Sable, Oscro, Virgil, Starks, Camden, Strawn, Rozetta, St. Charles, Fayette, Hennepin, Cresent, Radford, Jules, Beaucoup, Huntsville, Sarpy, Landes, Dorchester, Lawson, and Worthen series.

The Strawn and Hennepin series consist of glacial till. If you’ve read my initial post on geology and shovel testing, you will know that glacial till is the term for geological material that was dragged along and deposited by advancing glaciers. You will also know that finely ground silt was washed out of the melting glaciers and then picked up by the wind, forming upland loess deposits that bury the glacial till in many places. These loess deposits have not accumulated much new wind-blown sediment since the end of the Pleistocene, so most artifacts would be located at the surface or in the topsoil. The Rushville, Keomah, Sylvan, Sable, Oscro, Starks, Camden, Rozetta, St. Charles, and Fayette series soils consist of loess. The Dodge and Virgil series consist of a combination of glacial till and loess. The Cresent series consists of glacial outwash. It is basically alluvium, but very old.

And the Radford, Jules, Beaucoup, Huntsville, Sarpy, Landes, Dorchester, Lawson, and Worthen series all consist of Holocene alluvium, which can be found on the modern floodplains alongside the creeks.

Here is a map that puts this all into perspective:

 

Figure 9: Map of Soil Units within AOI in Peoria County, IL, classified by soil formation and history

Figure 10: Map Legend

The light brown units represent the upland areas where periglacial loess is lying directly on the surface. The orange units represent the slopy areas where glacial till is still exposed on the surface, unburied by loess, and the pink units represent the transitional areas that consist of both loess and glacial till. There are a couple of purple units that represent pockets of glacial outwash. The red units represent a Holocene floodplain along the banks of Senachwine Creek and one of its tributaries.

You’ll notice there is no residual soil, at least not on the surface. The bedrock is too deeply buried beneath thick layers of loess and glacial till in the upland areas, and beneath layers of alluvium in the lowland areas. There are very few places in this area in which the bedrock is naturally exposed. Unlike Texas, this landscape was transformed by the Pleistocene glaciers.

If you just want to know how deep to dig a shovel test, it’s safe to terminate your test at the B horizon if digging in ancient loess or glacial till. If digging in a Holocene floodplain, again, it’s wise to dig as deep as you can.

Fortunately, all this data is available in the field if you have a smart device with an internet connection. You can download the Soil Web app on your phone or tablet, and this can tell you whichever soil unit you’re standing on. The app won’t tell you how that soil series formed though, so you may have to look up more information on the soil series with a web browser.

 

How Not to Use the NRCS Data

Mistakes should always be a good opportunity to learn, so it stands to reason that one way to become more proficient at using and understanding the NRCS data would be to examine the work of people who are not using the data correctly, and seeing where they went wrong. There are probably many examples from which to choose, but a topic like this requires a deep dive into some minute details, and I only have the time or energy to take a deep dive into one body of work. I'm going to take a deep dive into the Texas Department of Transportation Potential Archeological Liability Maps (TxDOT PALM). By the end of this section, it will probably seem like I'm trying to cyberbully TxDOT, but that is not my intention (if I were going to cyberbully TxDOT, it would be for designing roads where I have to yield to people who are approaching from behind, but that has nothing to do with archaeology). I don't think the archaeologists or other specialists at TxDOT are any more incompetent than their counterparts at any other government agency, private company, or academic institution. I think misinformation is probably rampant throughout almost all these organizations, but I don't have the time or insider knowledge necessary to thoroughly critique all of them, so I'm just going to focus my efforts on scrutinizing the TxDOT PALM model for now.

The TxDOT PALM maps constitute a probability model designed to assist archaeologists with planning their surveys, by demarcating those areas that have a high, moderate, or low probability for surface sites or deeply buried sites, or any combination thereof (a deeply buried site would be any site in which artifacts are buried more than one meter deep). If you want to look at the model yourself, you can download the various files by district here. I can tell a lot of work went into this. The people at TxDOT who developed this model aggregated multiple datasets into a single set of maps, and though I was not involved in the model’s production, I’m pretty sure the NRCS Web Soil Survey was one of the datasets employed (along with extant water features), because the NRCS soil units seem to match up too well with some of the units in this model. Having reviewed this model carefully, I’m now going to demonstrate that its recommendations are very much at odds with the original NRCS data.

Let me start by explaining how I think the model was made. Again, I didn’t make it, so I can only speculate, based on my knowledge of GIS. But I’m pretty sure the developers used a polyline shapefile showing all the bodies of water in Texas, even small creeks and rivers. And I think they made buffers around those water features, under the assumption that most prehistoric sites would be found near water. That makes sense, I’ll give them that. Those buffers were probably amalgamated with other datasets, including the NRCS data, to create units with varying degrees of probability for locating deeply buried archaeological sites and/or surface sites.

Those map units that are closest to the bodies of running water are classified as having a high probability for deeply buried sites. That sort of makes sense. Running water deposits alluvial sediment. Alluvial sediment buries artifacts. So far, so good. But the problem is that creeks and rivers often do not have floodplains along their entire length. In many places, they cut through ancient formations without depositing any new sediment along their banks. This model is claiming a high probability for finding deeply buried archaeological sites in places where that is not physically possible—in places where the bedrock is so shallow that no artifact could be buried more than a couple feet deep. Let me show you.

Here is an example of a section of the TxDOT PALM data for TxDOT’s Dallas District. It falls within a portion of the section of Collin County that I showed you earlier:

 

Figure 11: TxDOT PALM Data Closeup in Collin County, TX

Figure 12: Map Legend

Here's a rundown of the numbers in the map legend and what they are supposed to represent:

0. Water

1. Low shallow potential, low deep potential

2. Low shallow potential, moderate deep potential

3. Low shallow potential, high deep potential

4. Moderate shallow potential, low deep potential

5. Moderate shallow potential, moderate deep potential

6. Moderate shallow potential, high deep potential

7. High shallow potential, low deep potential

8. High shallow potential, moderate deep potential

9. High shallow potential, high deep potential

The red units (Map Unit 9) represent areas that supposedly have a high probability for both deeply buried sites and surface sites. Now take a look at a map with one of those red high-probability units selected. Below the TxDOT PALM units, I’ve added the NRCS soil units:

 

Figure 13: TxDOT PALM high-probability selection overlaid above soil units

Now let’s look at a map of those NRCS soil units, with the TxDOT PALM data removed. I’ve selected one of the soil map units that was beneath the selected high-probability area. If you look to the right of the map, you’ll see that the Soil Map Symbol is HoB2, one of the symbols for “Houston Black clay.”

Figure 14: Houston Black selection

So this probability model is claiming that there is a high probability for both deeply buried sites and surface sites in Houston Black clay. Now, I think it’s right to claim there is a high probability for surface sites here. This is an upland area overlooking a body of running water. There are probably plenty of sites on the surface, or shallowly buried by biotic activity. But I can’t agree that there is a high probability for deeply buried sites here, because that is almost physically impossible. Houston Black clay does not contain any deposits of Holocene alluvium. It formed in residuum derived from weathered bedrock.

Maybe that’s a fluke. Let’s take a look at one of the other soil units beneath TxDOT’s high-probability unit:

 

Figure 15: Austin silty clay selection

Well, the Map Unit Symbol is AuB, which is code for “Austin silty clay, 1 to 3 percent slopes.” This belongs to the Austin soil series, another residual soil. According to the NRCS, in a typical profile of Austin series soil, the Cr horizon begins at about 74 cm. below surface. The Cr horizon is just a term for bedrock that is soft enough to break with a shovel. But the TxDOT PALM data claims that there is a high probability for finding sites buried deeper than one meter here. If you try to dig deeper than a meter here, you’ll be chiseling through chalky limestone, not finding an archaeological site. What about the next one:

 

Figure 16: Austin silty clay selection

That soil also belongs to the Austin soil series. The Map Unit symbol is AuC2, or “Austin silty clay, 2 to 5 percent slopes.”

Let’s take a look at another probability unit. I’ve selected a unit that is supposed to have a high probability for deeply buried sites and a moderate probability for surface sites (Map Unit 6):

 

Figure 17: TxDOT PALM model selection for area with high probability for deeply buried sites and moderate probability for surface sites

And now let’s see which soil unit lies beneath it:

 

Figure 18: Houston Black selection

Okay, this probability unit overlies Houston Black clay, which, again, cannot contain deeply buried sites.

Now let’s look at a third probability unit that supposedly has moderate probability for deeply buried sites and low probability for surface sites (Map Unit 2):

 

Figure 19: TxDOT PALM model selection for area with moderate probability for deep sites and low probability for surface sites

It matches up quite nicely with an NRCS soil unit labeled as LeC2, or "Lewisville silty clay, 3 to 5 percent slopes," which belongs to the Lewisville series (the fact that it matches up so well leads me to believe that the NRCS Web Soil Survey provided one of the datasets used in this model):

 

Figure 20: Selection of Lewisville soil series

The Lewisville series consists of alluvium, so at least technically it’s physically possible for it to contain deeply buried sites. However, The Lewisville series consists of ancient alluvium, not Holocene alluvium, so this landform has not accumulated sediment in a very long time. It would be very unlikely for anyone to find a deeply buried site here. Maybe a pre-Clovis site. In fact, all the sites here would most likely be close to the surface, yet the model claims there is a higher potential for deep sites than surface sites. In fact, I think there’s a pretty high potential for surface sites, but almost no potential for deep sites.

The TxDOT PALM model clearly contradicts the NRCS data in some big ways. Of course, who’s to say that the NRCS data are not wrong, at least in this spot? The NRCS Web Soil Survey is not perfect. It does contain inaccuracies. After all, the whole point of this soil survey is to help farmers, not to tell archaeologists about the formation and history of every square inch of land in the United States. So maybe TxDOT knows something the NRCS doesn’t.

I would consider that, except for two reasons. First of all, I’m pretty sure TxDOT used the NRCS data as one of the datasets that were amalgamated into this model. If you’re willing to use the data, the implication is that you think it’s correct, or at least good enough. If you’re using the data but your end product directly contradicts it in some fundamental ways, the implication is that you never really understood the data to begin with.

Second of all, I’ve personally been to the spot that I’m examining with these maps. I’ve walked over the creek exactly where that high-probability unit is supposed to be. There is no floodplain where a site could be deeply buried. The creek cuts through exposed bedrock. On either side of the creek, there is a very shallow layer of residual soil above the bedrock. There is a little bit of fluvial sand in some spots on the creek bed, and I guess that sand could bury a coin if you dropped it in the water. But even that sand isn’t very deep, and the water flows directly over slabs of stone in most places. My observations in the field have confirmed that the NRCS data are correct, at least in this location. Which means that the TxDOT PALM recommendations are at odds with actual scientific data and have no basis in reality.

I wouldn't go so far as to say that the people who created this model are bad archaeologists or pseudoscientists. I've heard, secondhand, that they don't really expect anyone to take the model as gospel. And I suspect that at least some of the people who built this model know that it contains a fair amount of physical impossibilities. So it may have been harsh of me to imply that the TxDOT employees who made the model never understood the NRCS data to begin with. The issue lies probably not with human ignorance but with the way that probability models are generated in ArcGIS. The process by which datasets are aggregated into a probability model is automated in ArcGIS, and the way that soil types are organized in the NRCS Web Soil Survey does not really lend itself to automated workflows. If you wanted to create a new probability model that actually takes into account whether a soil type consists of residuum or Holocene alluvium or something else entirely, you would need to make a list of each soil series that fits into each category and then select each map unit that falls within said category; there is probably no good way to automate that process. Maybe the people who built this model simply never had the time or resources necessary to make one that's actually accurate. So I can't really blame them for the product they made, but I still have to acknowledge that this product is detached from reality in some fundamental ways.

I have to wonder, how far removed can our work be from reality before we have to call it pseudoscience? In my opinion, this model has already crossed that line. I'm not going to call the TxDOT employees who made this model "pseudoscientists," but I'm going to be less charitable with those archaeologists who use this model uncritically to make decisions for them. That, I believe, is tantamount to pseudoscience. And I know that there are archaeologists who use this model uncritically, because I was a contractor for TxDOT, and some of those employees wanted me to conduct deep trenching via backhoe in places where it was not physically possible for a deeply buried site to exist, simply because that was what the model recommended. Aside from the fact that it was a waste of taxpayer money, it was also a waste of my time, and I could have used that time more effectively searching for sites in places where they could actually exist.

Correct (or at least, more correct) scientific information is readily available, it’s free, and at least some of it is fairly easy for laypeople to understand, yet this model largely contradicts it. In any other scientific discipline, if you repeatedly rely on a model that frequently advocates for probabilities that are actually physically impossible, when the data that could help you rectify those mistakes are easy to access, your peers would call you a pseudoscientist. But when archaeologists do it, other archaeologists don’t really notice.

Why don’t we notice? Archaeologists are usually all too eager to lambast laypeople as pseudoscientists if they diverge from the general archaeological consensus (and to be fair, such criticism is often deserved, especially when it comes to frauds such as Graham Hancock or Scott Wolter). But professional archaeologists frequently produce work that contradicts actual science, as in the case of the TxDOT PALM model, and rank and file archaeologists within cultural resources management seldom pay attention. Could it be that many of us don’t know nearly as much about science as we think we do, and our accusations of “pseudoscience” are simply due to deviations from accepted dogma by the accused, rather than an understanding of what actually makes those deviations pseudoscientific? Thus allowing the flimsy work of our peers and supervisors to slip through the cracks? After over a decade of conversing with fellow archaeologists and reading comments online, that’s the conclusion I’ve reached.

To be clear, that last part is just my opinion, and you don’t have to share that opinion. But over the years, it has become increasingly clear to me that cultural resources management is rife with misinformation, all the way to the top. I don’t have any particular ill will towards TxDOT (though I expect some ill will from TxDOT if anyone there ever happens to see this obscure blog post). TxDOT has competent specialists who have called me out on my own careless mistakes, and I might talk about those mistakes in this blog if they become relevant. I just wanted to use the TxDOT model as an example, to illustrate the misinformation and lack of comprehension so pervasive throughout all levels of cultural resources management—in every state, every corporation, every government agency that employs archaeologists. If no one corrects you, how will you learn from your mistakes? And how can the young and inexperienced be corrected if the people at the top don’t know nearly as much as they think they do?

Correction: An earlier version of this blog post mistakenly identified the Altoga soil series as having formed within residuum rather than alluvium. The map has been updated to reflect this correction.

Updated May 22, 2024

 

Field Safety Part III: Man-Made Horrors

As frightening as nature may seem at times, humans introduce a variety of man-made dangers to their own environments. Vehicles, heavy machinery, utilities, and noxious chemicals all pose a threat to field archaeologists.

Driving

The most dangerous thing that any archaeologist does on a daily basis is driving, which is a danger we share with members of every profession, even office workers who never go outdoors. Many motorists don’t seem to understand this danger, which makes the roads more hazardous for the rest of us.

Heavy Machinery

Though most archaeologists don’t operate heavy machinery themselves, we often have to monitor construction projects where backhoes and bulldozers are present. In Texas, many archaeologists use backhoes to test alluvial soils for deeply buried sites; if we aren't operating the machinery ourselves, we generally have to stand near the trench to keep an eye on the soil. This puts us at risk of injury if we’re not careful around the machines. As a general rule, wear a hardhat around these machines, and make sure the operator can see you at all times.

We also survey a lot of agricultural fields, and farmers harvest these fields with combines. It is extremely dangerous to be in a field while a farmer is driving a combine harvester through it, especially if the crops are so high that the farmer can’t see you. In my home state of Illinois, corn usually grows much taller than human height before it is harvested, and anybody walking around in the corn is virtually invisible. If a farmer accidentally runs into you with a combine, the demise you will meet is far more gruesome than I want to think about. If you have to survey a field, but the farmer is harvesting that day, the solution is simple: don’t survey it that day. It can wait, and any employer who says otherwise is not worth working for.

Utilities

We spend a lot of time digging holes, and that means we risk hitting buried utilities. Some utilities are more dangerous than others. If you break a buried water line with your shovel, that’s a problem, but it won’t kill you. If you strike a buried electric line with your shovel, the current could electrocute you.

Figure 1. Junction box connected to buried electric cable. The buried cable provides the power feed to an irrigation control system. The buried cable is not marked, and a misplaced shovel test could come into contact with it.

Gas pipelines can react explosively if broken, but fortunately for field archaeologists, it’s very difficult to penetrate a gas line with a shovel. The pipes are typically made of metal or very thick plastic. This means that you probably won’t blow yourself up by digging a shovel test over a buried gas line, but you shouldn’t do that anyway.

However, sometimes we monitor heavy machinery, and backhoes can easily damage gas lines or other utilities. If a backhoe breaks a gas line, that could be fatal for everyone in the vicinity. If a backhoe comes into contact with an overhead power line or buried electric cable, the result will probably not be immediately fatal, but it could quickly become fatal if people make bad decisions. If this happens, the operator should stay in the cab. Nobody in the vicinity should walk within about 30 feet of the machine, because the ground all around the machine will be energized. Simply walking towards the backhoe could cause you to be electrocuted.

Pesticides and Fertilizers

You should not be walking in an agricultural field while the farmer is having fertilizer sprayed. Many farmers in the United States use anhydrous ammonia fertilizer to replenish the soil with nitrogen. Ammonia fertilizer can severely irritate or burn skin upon contact. Inhalation of ammonia can make it difficult to breathe. If you are sprayed with fertilizer, this will probably be a medical emergency.

Farmers also treat their fields with chemical pesticides. One of the most commonly used pesticides is Roundup, the main ingredient of which is glyphosate. Roundup can irritate skin upon contact, but that isn’t the real danger. Glyphosate is now known to be a carcinogen that can lead to lymphoma or leukemia.

Fencing

We often have to climb over fences as we move from one parcel to the next within our survey areas. On many farms and ranches, the preferred form of fencing is the barbed wire fence. These are not difficult to cross, but a mishap can leave you with an open wound or twisted ankle. The sharp barbs on a barbed wire fence can puncture your skin or even tear large gashes in your flesh. Recently, I was climbing a fence as I’ve done many times before, but this time, my foot got caught as I tried to swing my leg over the top of the fence. As a result, I twisted my ankle and body slammed myself onto the ground.

Some farmers also use electric fences. These can be uncomfortable to touch, but are not life-threatening, because farmers do not put enough amperage through the current to kill someone.

Hunting

Many farmers and ranchers hunt on their property (and many poachers hunt on the property of others). Hunters don’t always pay attention to where their bullets will land if they miss their quarry. If you are surveying during hunting season, the best advice is to wear an orange vest.

The Healthcare and Insurance Industries

It’s no secret that healthcare in the United States is a mess. The cost of healthcare is absurdly high, but employers are required by law to provide workmen’s compensation for injuries incurred at work. Many employers would find it difficult to pay these medical costs out of pocket, so they need insurance. To get insurance, they have to enact the policies that the insurance companies want.

The problem is that insurance agents have no idea what archaeologists actually do, and they tend to lump us in with whatever industry our clients belong to. That means, if you are conducting an archaeological survey for a gas pipeline, the insurance company (and your employer) will want you to follow the same safety rules you would expect for a pipeline welder, even though the work we do is completely different. We don’t face the same dangers that pipeline welders or construction workers face. The dangers we face are just as real, but they are very different. This is irrelevant to most insurance companies, which expect us to wear hardhats all the time, even in wide open fields where there is nothing that can fall on our heads. I once had a client that expected me to wear fire-retardant clothing in the field all day, which actually made my job more dangerous. Since I was not doing any "hot work" (cutting or welding metal), there really wasn't any need for FR clothing, but it did make it a lot more likely that I would overheat while trekking through the mountains all summer.

This is the comical reality of corporate “safety.” Corporate safety rules require us to take measures that are completely unnecessary for the work we do, while overlooking the very real threats we face. Such as angry bulls—no hardhat will protect you from belligerent rough stock. There have been times when I have had to deliberately disobey inane corporate safety rules because I knew that compliance would, at best, make my life much more difficult without making me more safe, or, at worst, actually make my situation more dangerous. I won't name the corporations that made these absurd demands, at least not in this blog post, but I will make it clear that I won't work for them again.

This is all the more reason to know how to handle yourself in the back country. All too often, the people in charge of your “safety” at the corporate level have no idea what you actually do for a living, so you need to be able to trust yourself and your own judgment when the mountains are getting steep and rugged, and lightning starts to flash across the sky. You are responsible for taking care of yourself and looking out for your colleagues.

Closing Thoughts

If you are injured, that doesn’t mean you’re a bad archaeologist, or that you don’t belong in the field. It happens to everyone who does difficult fieldwork. Even if you’re not physically able to perform the duties of a field technician, that doesn’t mean you can’t be an archaeologist. If you’re wheelchair-bound, for example, you can’t realistically participate in an archaeological survey, which comprises most of the paid work in CRM archaeology. But there are other jobs you can do. There are lab technicians who analyze and curate the artifacts found in the field, and GIS technicians who work with the geospatial data. There are even jobs in academia, but to be honest, these are scarce and highly competitive (deciding to become an archaeology professor is probably about as realistic as deciding to be a successful rockstar). If you have the brains to understand the subject matter well, I hope I can welcome you into the world of archaeology, regardless of whatever physical disability you might have. I think every profession could use a little more gray matter.

I don't want to undermine the role that physical prowess plays in CRM fieldwork, but I still wish field techs were valued more for their thinking skills than their digging prowess. This is partially because I was valued more for my physical strength than my cognitive skills for most of my career (at risk of sounding arrogant, I am arguably stronger then most people, and I have personally dug thousands of shovel tests in addition to performing other physically demanding tasks, which made me an asset to my employers during my long career as a field tech—but I would like to think that I had more to offer than just physical strength). We are supposed to be scientists, first and foremost. Crew chiefs are supposed to cultivate knowledge and understanding within their field techs. But the sad truth is that many field techs and crew chiefs barely know the basics, and when they do try to impart information to the younger generation, it is often completely wrong (The man who taught me how to shovel test at my first CRM job had a PhD, and still managed to spread more misinformation than legitimate knowledge).

Safety, fitness, and knowledge are all closely linked. You can't be safe in the field without a certain level of fitness, nor can you be safe in the field without a certain level of knowledge about the dangers you face, and how to react appropriately to those dangers. The job is not worth your life, and your safety should be a higher priority than doing "good archaeology." But at the same time, the whole point of archaeology is knowledge, so if you're not going to do it well—with a solid understanding of the subject matter and the science behind it—it sort of defeats the purpose of doing it in the first place.

Updated April 11, 2024

Field Safety Part II: Dangerous Flora and Fauna

While Part I of this post focuses on the hazards of climate and weather, including extreme heat and cold, the second part will focus on dangerous plants and animals encountered in the field.

Dangerous Wildlife

Dangerous wildlife is not as common in the United States as it once was, as humans have driven grizzlies and bison from their former habitats. But in some places, there are still wild animals that can kill you.

Venomous snakes are common across the United States. The most iconic may be the rattlesnake. There are many different species of rattlesnake, which can be found from coast to coast. If you do fieldwork long enough, you will probably startle a rattlesnake at some point and provoke it into shaking its tail. All species of rattlesnake are highly venomous and their bites are potentially fatal to humans. The eastern diamondback rattlesnake, found only in the Southeast, is the most venomous snake in North America. The Southeast is also home to the copperhead, water moccasin (cottonmouth), and coral snake, all of which are venomous. Of the three, the copperhead is the most innocuous, as its bite is seldom fatal to humans. A bite from a water moccasin or coral snake is much more likely to be fatal if left untreated.

In the event of a venomous snake bite, go immediately to the hospital. If possible, take a picture of the snake so the hospital staff can identify the species and know which type of antivenin to administer. If you have a long drive to the hospital, you may want to tie a tourniquet around the bitten limb to prevent the venom from circulating around your body. The lack of circulation may cause you to lose the limb, but most would prefer that to death. Trying to “suck out the poison” through the wound will achieve nothing.

Snakes are not the only venomous animals in the field. Certain spiders or scorpions can also bite or sting you with potentially harmful (but seldom fatal) venom. The most common venomous spiders in the United States are the black widow and brown recluse. Their bites may hurt like hell but they probably won’t kill you. The same can be said for the tarantula, which has very weak venom, but its bite still hurts because its fangs (chelicerae) are so big. The most venomous scorpion in North America is the bark scorpion, whose sting is incredibly painful, but seldom results in death for adult humans.

Venom is not the only means by which a wild animal can harm or kill you. Some fauna apply trauma more directly—sometimes in an attempt to prey on you, or sometimes in an attempt to defend themselves from you.

The American alligator is one such animal. They occasionally kill and eat people, though they are not as likely to do so as Hollywood would have us believe. They are not as aggressive as the crocodiles of Africa or Australia, and are generally timid around humans. They will probably not pursue you on dry land. But if you wade or swim in water where alligators live, they may see you as an easy meal, and consequently kill and eat you. What you should take away from this is that, if you are doing fieldwork in gator country, stay on land (or in a boat), and refrain from swimming in ponds, canals, or bayous.

The mountain lion is another animal that occasionally stalks and eats humans, though not very often. They are common in the Western states, and though the eastern subspecies of cougar is almost extinct, young western cougars have been found wandering far to the east (as far as Connecticut) in search of mates.

The bear is a creature that is often maligned by pop culture as being more dangerous than it is, but make no mistake—all bears still have the potential to be dangerous to humans. There are three species of bear in the United States. The polar bear can be found in northern Alaska. It actively hunts humans and is very aggressive. You will not survive a polar bear attack, but you will almost certainly not have to worry about that, unless you are one of the few archaeologists who does fieldwork in the Arctic. The grizzly bear (a subspecies of the brown bear) can be found throughout Alaska, and in some small pockets of the lower 48 states, such as Yellowstone National Park in Wyoming. Grizzlies occasionally prey on humans as well, but most field technicians in the United States do not work in places where grizzlies live. The only other subspecies of brown bear found in North America is the Kodiak bear, which lives on Kodiak Island in Alaska.

The vast majority of field techs in the United States don’t need to worry about polar bears, grizzlies, or Kodiak bears. For most of us, the only bear we will encounter in the field is the American black bear. The American black bear is much smaller and more timid than the grizzly, Kodiak, or polar bear, and it seldom attacks humans for any reason. When they do attack, their attacks are typically not motivated by predation. Black bears feed mostly on bugs and vegetation, and raid dumpsters when they get a chance. When humans approach them, they usually flee.

In short, the black bear is basically an over-sized raccoon, but keep in mind that even a raccoon would be dangerous if it weighed 300 lb. Black bears are unpredictable, and capable of immense violence when the mood strikes them, which could be at any time. I know a man who was attacked by a black bear that ate his leg while he was still alive (we once had a contest to see who had the highest tolerance for pain, and he won). So respect the black bear, and try not to surprise and provoke it, because it can still kill and eat you if it wants to do so.

In general, large carnivores are not as dangerous to humans as large herbivores are. Mountain lions and alligators don’t often prey on people, and black bears don’t really see humans as food; if they attack at all, it is usually because they think they are defending themselves against a threat. But large herbivores such as moose, bison, and elk can be highly aggressive and territorial, especially when in rut.

Bison were once common across the Great Plains, but today they live wild in only a few pockets of the United States, such as Yellowstone National Park in Wyoming, or Custer State Park in South Dakota. Most field archaeologists will not encounter a wild bison. However, many ranchers now raise captive bison for beef, so it is still fully plausible for the average archaeologist to survey land where bison are present. I have personally surveyed a couple of bison ranches myself, and the bison that lived there were decidedly unfriendly. If a bison starts snorting at you and approaches you, get away from it. It doesn’t want you to pet it. It’s thinking about trampling you to death.

Moose and elk still live wild in the northern parts of the United States. Moose, in particular, are very dangerous during their mating season. It is very plausible for archaeologists to encounter an angry moose in the north woods of Maine, Michigan, or Minnesota.

In the South, invasive feral hogs are common, and their range is growing. They generally do not attack humans unless threatened, but when they do attack, they can gore and kill people with their tusks.

The animals I’ve discussed above all pose realistic threats to field archaeologists, but the average archaeologist won’t encounter them every day. Keep in mind that even something as small and ubiquitous as a wasp or bee can be fatal to some. A wasp sting may be a minor annoyance to most, but it can kill someone with an allergy. And allergies can onset at any time in life. I was stung by bees and wasps many times when I was young, with no ill effects, but shortly before I turned 32, a wasp sting put me into anaphylaxis and nearly killed me.

If you have a life-threatening allergy of any kind, you should carry a pair of EpiPens (or some other brand of epinephrin injection device) into the field with you. Unfortunately, EpiPens are not meant for excursions into temperatures exceeding 86˚ F, while fieldwork often requires that we spend eight hours a day in temperatures up to 100˚ or more.

In my opinion, the most dangerous animal that most archaeologists will encounter almost every day in the field is the humble tick. The tick’s bite is not life threatening or even painful on its own, but it can transmit any number of debilitating diseases. The most infamous of these is Lyme disease, which is conveyed by the bite of the deer tick. But ticks can infect you with far more than Lyme disease, and every species of hard tick in the United States is a disease vector. In case you think these diseases are not so bad, untreated Lyme disease can lead to arthritis and permanent neurological damage. Alpha gal allergy, which can be caused by the bite of the lone star tick, is a permanent allergy to red meat (meaning you can’t eat steak or cheeseburgers anymore).

Here is a list of some of the tick species in the United States and the diseases they carry:

Deer Tick or Black-Legged Tick (Ixodes scapularis)

• Lyme disease
• Anaplasmosis
• Babesiosis
• Powassan virus
• Ehrlichiosis
• B. miyamotoi disease

Lone Star Tick (Amblyomma americanum)

• Ehrlichiosis
• Heartland virus disease
• Southern tick-associated rash illness (STARI)
• Bourbon virus disease
• Tularemia
• Alpha gal allergy

American Dog Tick (Dermacentor variabilis)

• Tularemia
• Rocky Mountain spotted fever

Brown Dog Tick (Rhipicephalus sanguineus)

• Rocky Mountain spotted fever

Groundhog Tick (Ixodes cookei)

• Powassan virus

Gulf Coast Tick (Amblyomma maculatum)

• Spotted fever

Rocky Mountain Wood Tick (Dermacentor andersoni)

• Rocky Mountain spotted fever
• Colorado tick fever virus
• Tularemia

 Western Black-Legged Tick (Ixodes pacificus)

• Lyme disease
• Anaplasmosis
• B. miyamotoi disease

Soft Tick (Ornithodoros)

• Tick-borne relapsing fever

Ticks are not born with the pathogens that cause these diseases. After hatching, the larvae can become infected with these pathogens when they feed on the blood of infected vertebrates. Then, after growing into nymphs, they can spread these viruses or bacteria when they bite new hosts (including people). Field archaeologists are always walking around in dense thickets or brush where tick nymphs and adults are waiting to latch onto passing animals, and we frequently find ticks crawling on us by the end of the day. Unfortunately, tick nymphs are so small that they can bite you, feed for a while, and be on their way before you even realize they’re attached to you. You can be infected with Lyme disease or some other pathology without knowing you’ve even been bitten by a tick.

If you are bit by a tick, remove it with tweezers, trying to keep the mouthparts intact (rather than letting the mouthparts break off and remain in your skin). Keep the tick’s body in case you need to identify it later, or in case you need to prove you were bitten while at work.

Dangerous Livestock

Domesticated livestock can be as dangerous as the wild herbivores I’ve discussed above, and they are much more common. Every field archaeologist will have to survey a field full of cattle at some point.

Cows are generally as docile and easy-going as any large mammal can be, but many ranchers and farmers will graze bulls alongside their cattle, at least for part of the year. Bulls are not very nice. A bull attack will probably be fatal for you, if you fail to find shelter before it gores or tramples you. And there is often no shelter on the open range.

Even female cows can be unfriendly during calving season (springtime), because they are protective of their newborn calves. If you get too close to a calf, a female cow may charge you. I’ve been charged by a cow during calving season. If that happens, don’t run. In general, don’t turn your back on any livestock that might charge you (especially goats). If a cow charges you while you have your back turned to it, turn to face it and stand your ground. If a bull charges you, standing your ground isn’t going to work.

Even horses can be dangerous to the uninitiated. Horses are not known to be as violent or aggressive as bulls, but a kick from a horse can still be life-threatening. Field archaeologists who are unfamiliar with livestock can absent-mindedly stand behind a horse and take a hoof to the head if something provokes the animal. Even an attempt to feed a horse can result in broken fingers if you don’t know what you’re doing.

Dangerous Plants

Most of the plants you will encounter won’t be able to kill you, unless they’re poisonous and you decide to eat them. I’m not going to discuss the various poisonous plants and mushrooms that you might encounter in the field, because that’s an entirely avoidable hazard. Just don’t eat strange plants you find in the wild.

However, even if you don’t eat them, many plants can still cause irritations or minor injuries.

One of the most infamous is poison ivy. Poison ivy, like its cousins, poison oak and poison sumac, produces an oil known as urushiol, to which many people are allergic. If you are allergic to poison ivy, the urushiol will cause severe itching after coming into contact with your skin. If you accidentally come into contact with poison ivy, you can spare yourself a future of skin irritation by washing away the oil before your skin reacts to it. Tecnu is specifically designed to wash the urushiol from your skin, but ordinary dish soap can be effective as well. Keep in mind that the itching is not caused directly by the plant; it’s caused by your immune system, as it reacts to something it perceives to be a threat. You don’t really build up an immunity to poison ivy because your immune system is the problem; that’s what an allergy is. Even if you’re not allergic now, you can become allergic after repeated exposure.

Figure 1. Poison ivy

Poison ivy is a part of life for field archaeologists, especially if you work east of the Mississippi. You can’t avoid it, even in winter, when all the plants around you seem dead. The leaves of the poison ivy plant may be senescent, but the roots and vines contain urushiol as well, and you can dig up the roots while shovel testing and rub the urushiol all over your hands while screening the soil. If all the leaves are dead, you may not even realize that there is poison ivy in the vicinity, unless you see the telltale red, hairy vines growing on nearby trees. This is yet another reason to wear gloves while working.

Poison ivy is ubiquitous in the eastern half of the United States, but it won’t cause any severe harm. For most, it’s a mild annoyance. Other plants pose a more severe threat.

Giant hogweed and wild parsnip are two invasive weeds currently spreading across the eastern half of the United States. Both produce a sap that will severely burn your skin if it comes into contact with your skin under direct sunlight. Both are extremely harmful, but hogweed is more so. A giant hogweed burn will be painful for several months, and your skin will remain sensitive to sunlight for years to come. This burn is not caused by an allergy. Everyone is vulnerable to giant hogweed and wild parsnip.

Not all plants rely on saps or oils to induce pain in humans. The many species of cactus plant in the United States have sharp spikes that can easily impale clothing and skin. Many other trees, shrubs, and vines—such as the hawthorn, locust, bois d’arc, mesquite, brier, and bramble—have sharp thorns that can also puncture skin (or your eyes, if you are particularly unlucky). As of the time of this writing, I have had the tip of a hawthorn tree’s thorn imbedded in my right leg for over a year.

Figure 2. Prickly pear cactus in west Texas

All the plants I’ve described above can be painful or irritating, but they seldom induce fatalities in human beings. However, dead trees and branches can fall on people and kill them. A dead tree that has been weakened by rot or fire, or perhaps made unstable by the erosion of the soil beneath it, can be at high risk of falling over. If you are beneath a large tree when it falls, it will kill you. Even healthy trees will have dead branches hanging precariously in their canopies, ready to fall on an unsuspecting head at any moment. These dead branches are known to foresters as “widow-makers.” A walk through any forest may reveal dead trees or branches in unstable positions, and field archaeologists should be wary of them at all times.

Figure 3. Dead tree leaning into the branches of a live sycamore. As this dead tree continues to decompose, it will become more unstable, until it falls to the ground.

I wish I had advice on how to treat the victim of a falling tree, but the truth is that if a large tree falls on you, it will probably be fatal. As I’ve been taught by wildland firefighters, the only safe tree is “no tree.”

Updated on April 9, 2023