Wednesday, July 24, 2013

Day 17: Paleoethnobotany and Starbucks Coffee

Day 17- Paleoethnobotany, People and Plants in the Past

Talk about your alliteration! Get it? Well, I enjoyed it. Yes, Paleoethnobotany is the study of ancient peoples through the study of the plants remains, which have survived in archaeological contexts. Paleoethnobotany is an archaeological sub-field of study which uses the identification of plant remains, in combination with the ecological and cultural information we have thanks to modern plants, are able to study the use of wild plants, origins of agriculture and domestication, and the co-evolutionary nature of the human-plant interactions across time.

For this lecture, Dr. Kandace Hollenbach from the University of Tennessee at Knoxville was kind enough to come to Monticello to shine the light of paleoethnobotany on us field school students. Dr. Hollenbach's studies focus on the prehistoric foodways among hunting-gathering and agricultural peoples of the southeastern US, gender and identity roles, and the use and meaning of landscape among those hunting-gathering peoples as well.

Dr. Hollenbach's lecture focused on the rituals, use, and ancient peoples' thoughts of plants, her bottom line to us was, "people effect plants and in return the plants effect the people as well." People use plants for a multitude of reasons, they procure, process, prepare, consume, discard them, and frequently they are not preserved. The fact that they are not preserved leaves no evidence for paleobotanists and archaeologists. In terms of plant (either in the form of pollen or phytoliths) preservation, dry conditions are best, and wet conditions are destructive. Wet conditions can result in water logged, anaerobic conditions, meaning there is not enough oxygen for microbes to live and destroys the botanical remains completely. Plants can also be carbonized, this occurs when botanical remains become trapped and squeezed between sediments, are turned into carbon as they deteriorate, and since animals and plants get zero energy from carbon, the plant is left alone.

The preservation of micro/macro-botanical remains are then left to procurement. Procurement assumes the food item was gathered, harvested, or purchased.
Procurement = eating = digesting = paleofeces (coprolites)
Harvesting = food processing = eating = coprolites
OR Harvesting = processing = byproduct, then burned for fuel or trash disposal
Harvesting can also lead to the byproduct simply decaying on its own, whether it is simply disposed of, or as spill.

In the field of paleoethnobotany, certain biases are necessary to consider when reviewing a sample, these include:

  • byproducts being over-represented relative to the edible portions
  • items not cooked with fire are under-represented 
  • items that burn to ash (e.g. leaves) or unrecognizable mass (potatoes, etc.) are under-represented. 
  • small, fragile items that don't burn well and do not withstand mechanical damage (freeze/thaw and recovery techniques are under-represented
One also cannot go directly from numbers of remains located to the importance of crops in any civilization's lives. Instead, cross-reference your finds (i.e. a high number of corn remains) with the ethnohistorical accounts of crops and diets to enforce the located evidence. However in the reality of the historical record, white European men (early colonial settlers) simply do not write about the native's crops or dietary practices.

The recovery stage of both macro and micro-botanical remains is accomplished a process known as flotation, which can either be mechanized through a "float tank," or by hand. The next step is to analyze the remains under a microscope and identify them. The use of a modern comparative collection can come in handy during this stage and most collections collect and burn modern samples for precise references.

The interpretations of micro and macro-botanical remains focuses in on the subsistence and foodways of ancient peoples, the procurement, processing, storage, preparation/cooking, consumption, and discard practices offer a picture of how people are living on the site. For example, plant domestication can be followed by the changes through time and across location (regional patterns) to the crop. Paleoethnobotanists are finding that people are choosing larger seed sizes as time moves forward as well as a thinning of the seed coat. Wild seeds need their coating in order to survive the winters but domesticated seed are preserved through storage, resulting in the eventually thinning of their coats. Thin coats also sprout first and produce the most seeds for the next season's harvest as well. The importance of the coat lies not only in the agricultural value, aids in the successful identification and separation of wild seeds and domesticated seeds, since coats can be used to differentiate between the two. Plants co-evolve as people interact in their lives and there are changes in both the plants and people. People get tied down to spots with agricultural plots, going from a once continually moving, hunting-gathering society, to a settled, stable one illustrates the mutual domestication plants had on people as well!

Dr. Hollenbach then transitioned into the second portion of her lecture, which surrounded her research involving human behavioral ecology, arguing the costs and rewards of walking to gather or hunt a food source. The central place foraging theory is used to mathematically point out characteristics in people's behaviors, by solving for the return rate of the energy spent to collect the food item, with the energy obtained from the item, in consideration with the time spent to find, collect, or hunt the item. This is achieved through ethnohistorical accounts of the individual peoples, in combination with experimental archaeology, which Dr. Hollenbach admits to sending her grad students on a walking expedition to achieve.

*handling cost outweighs carrying cost
Squirrel = High handling cost (30kg)

  • walking cost (tied to slope and distance of specific landscape)
  • amount of time it takes to actually catch a squirrel
  • minimal gain in energy obtained
  • travel cost doesn't matter as much
Spawning Fish = Low handling cost (30kg)

  • assume the people know their surrounding landscape and know the location and the worth of the river where this resource can be continually found. 
  • travel cost matters
Given this mathematical breakdown of the cost vs. reward of various food sources, Dr. Hollenbach can hypothesis that most campsites of ancient people are made with a low cost food source close in distance. For example, fish are a reliable food source, they can always be found in a nearby river, whereas deer could be anywhere, and would therefore cost more to locate and carry, but if found would outweigh fish in the energy gained category. So it all comes down to how much energy you are willing to spend in the hopes of gaining equal or more energy in return for a specific food source/item.

Back to the micro and macro remains, these can also be used to identify the social and political organization of people, or any socio/politcal shifts which occurred throughout time within that society as well. In today's world think about your own personal reactions when you notice someone walk passed you holding a Starbucks coffee cup rather than a local, fair trade coffee brand/cup, certain social and economic assumptions are made on your end, and a social status signal is put out by the other person (the one holding the coffee cup). Certain aspects of our personal identity can be based on our favorite foods. MIND BLOWING! Think about that the next time you are going to treat yourself to a cup of brew- will you go commercial or local?

I promise to keep catching up on my blog updates- it is such a commitment!

Sunday, July 7, 2013

Day 16: A Tale of Sex, Love, and Romance

Day 16- The Role of Pollen in Archaeology

First, a huge thank you goes out to Dr. John G. Jones, Associate Professor of Anthropology at Washington State University, who was our guest lecturer for this lesson. He exuded energy and passion for the topic of palynology, opening his lecture as a tale of sex, adventure, and romance all about pollen. Needless to say, this gentleman was a true character, and equally kind to us students as he was to the professional staff.

Pollen is essentially and simply plant sperm with an outer shell made out of the genetic material, sporopollenin, which is the tough outer walls of spores and pollen grain, which is chemically very stable and is usually well preserved in sediments. Pollen is capable of being extracted from coal, and a 310 million year old pollen sample was found from a shale fragment from Mongolia, pollen will last. The only exceptions to this are when fungus or bacteria destroy the pollen.

Insect pollination is the most effective- plants attract bugs with pheromones from flowers, some plants make very little pollen and use their pretty flowers or fragrance to attract the insects to carry their pollen, or in the case of the pine tree, the plant may make a ton of pollen, pine trees make a billion polygrains in order to reproduce. Pollen wears and weathers out of rocks and people then breathe them in (allowing for location of bodies for example).

Pollen studies are used in fields such as the oil industry, medicine, bee keeping, forensic science, and of course, archaeology. In the oil industry, the oil has to be a certain age and maturity before it produces, so it is necessary to know how old the maturity of the sediment is, and whether it holds oil or just gas. Approximately 91% of all palynology worldwide is for various oil industries, which pays about $500 a sample, with about 4,000 samples requested a day as “rushed work,” and the lab receives 10% of the profits. Pollen is used in medicine for allergy testing. For example, a single vile of ragweed is $450 and is needed for all main allergy testing done by doctor’s offices. Forensics uses pollen testing just as you have probably seen in any criminal drama television show, such as Law and Order, or Bones.

Most importantly pollen is used in the field of archaeology, mostly coprolites (fossilized feces), and as Dr. Jones likes to say, “Pull up a stool, I’ll tell you all about it.” As in many cases, the bathroom holds the key to the way a society ate and lived. A stool can tell us the origins of agriculture, deciphering the earliest crop dates, and agriculture style (burning, fertilization, etc.). The sediment at Monticello perfectly conserves the pollen from oxidization which kills pollen, and the thick red clay also coats the pollen grains, keeping fungus from killing the pollen. Palynologists have, for example, taken pollen samples from ground stone to tell what people were harvesting, preparing, and eating.

The process of pollen soil sample is extremely complicated. The first step is to dissolve the soil away, leaving the pollen. Hydrochloric acid is used to isolate the pollen, then sands, silts (silicas) are removed with hydrochloric fluoride, the sample is then washed in potassium hydroxide, which can dissolve skin, but leaves the pollen, and in order to remove the organics acetolysis is used, it is explosive in water, but leaves the pollen, the minerals then need to be removed, a pyrite and tourmaline causing the minerals to sink and the pollen to float. The Monticello soils are very difficult to clean, due to the thickness of the clay, and not all pollen collected is identifiable.

Corn (maze) barley, oats, and wheat, along with all grass have similar looking pollens. The oldest maze pollen to have been located to date goes back to 52000 BCE and was produced by plants which did not produce corn cobs, yet still produce a sugary rich stem. Maze in the new world was possibly first domesticated to make sweet beer brew (honey was in Mesoamerica and cocoa), sweets from corn is brewable from the stocks.

Pollen in archaeology is taken with soil cores, samples from parts of the ground never exposed to oxygen, and core samples, used for radiocarbon dating (the chronological record of changes in pollen throughout time). A vibracore collection allows for the soil to be brought to surface without disrupting the sediments. Pollen samples are also collected from sidewalls (profiles) of the strata of a quadrat, what is known as a profile pollen sample, which means that every 5cm of the sidewall a pollen sample is collected from the bottom-up, and then a pollen diagram is created to illustrate the break-down of certain pollens.

Aside from pollen, phytoliths (siliceous plant remains) can also be useful in archaeology. Phytoliths are produced within cells of plants, and are strong in areas where pollen is weak. Whereas with pollen, grass could not be identified, with phytoliths grass is identifiable. The smaller the sample of phytoliths, the better the integrity, and these samples should be taken from the center of your feature (i.e. sub-floor pit found in quadrat). Both pollen and phytoliths are simply more key pieces to the historical puzzle which archaeologists are charged with attempting to solve over years of collecting and putting together piece after piece- slowly but surely. 

Day 15: In Archaeology, Geology, Rocks!

Day 15- Geology and Rocks on Site at Monticello

My apologies, due to the rain and the hectic schedule of the last couple of weeks, my blog updates have fallen behind. But I can quickly update you on the lectures and experiences of the field school- it has been unbelievable!

The first thing you need to know about geology, which may seem simple, but often gets over looked- rocks vary regionally. The second step to understanding geology is being knowledgeable about the Wilson cycle. The Wilson cycle refers to theopening and closing of ocean basins caused by movement of the Earth's plates. The Wilson cycle begins with a rising plume of magma and the thinning of the overlying crust. As the crust continues to thin due to extensional tectonic forces, an ocean basin forms and sediments accumulate along its margins. Subsequently subduction is initiated on one of the ocean basin's margins and the ocean basin closes up. When the crust begins to thin again, another cycle begins. 

In the specific case of the field school, Monticello is located in the Blue Ridge Mountains of Virginia, which have eroded into the coastal plain. A long time ago, when ancient Africa and North American collided, Atlantic fills with lava flows forming black basalt build ups, forming the mountains, the mountains then erode, island chains slams in, thus causing a continual series of mountain forming events. This black basalt build-up was then squashed with heat and pressure and morphed into greenstone. The Atlantic Ocean then erodes these mountains to form modern-day Virginia. The lava continues to build, spills out, and forms tiny payers between basalt, forming beach dunes and various landscapes. Silt stones formed together with heat and pressure to produce quartz. This information is important due to the fact that greenstone and quartz are the most common rocks found at Site 8 on the dig at Monticello. Quartz is also resistant to weathering and the most common and resistant mineral on the planet. It is capable of surviving chemical weathering since it does not oxidize at all.

The teaching assistant who gave this lecture, Devin Floyd, explained to us that rocks in archaeology make up everything that came before the people and the buildings and the history. He also explained that we, as archaeologists need to question what is and is not a rock artifact, and we can answer this question with another question: Has the rock been altered (or worked) by humans? This is how archaeologists know if the rock fragment is an artifact which needs to be kept or simply thrown away.

At Monticello quartz sand has formed into quartz and mineral massive quartz cannot be tested or replicated. Seems and cracks form in the parent material, then groundwater passes through, and silica accumulates and fills the space with quartz crystals, the parent material decomposes, leaving the quartz vein to grow. Along with quartz deposits, Goethite, named after the German polymath Johann Wolfgang von Goethe, has been found. The mineral was used for devil’s dice (the mineral breaks in perfect cubes) and was used to make game pieces and toys at Monticello.

Back to knowing whether or not a piece of quartz has been worked or not, quartz has similar properties as glass, it creates sharp edges when broken and was primarily used for projectile points (weapons, knives, etc.) for prehistoric peoples. Local quartz found on Monticello have lots of heat fractures and small pieces were worked til thick and blunt before they break with concloidal fractures (cone of energy breakage), and the bulb in the rock can tell us if it was struck or worked in any manner to be cut down and used. Slate and soapstone are also very important artifacts which can be found at Monticello. Slate gives off a high-pitched ring if struck and we used in chimney chinking and soapstone is metamorphic and as its surface is refined, it turns black (steatite) and can then be used as gun flints which have been found on slave sites. This is a key piece of evidence which has recently been discovered by archaeologists and has led to the interpretation that the slaves on Monticello (and other sites where the steatite has been found) had access to guns- most likely for hunting. These are the important developments in archaeology which geology has led to and one of the many reasons it is an important aspect of the historical record. 

Sunday, June 16, 2013

Day 10: Stratigraphy, Plan Drawings, and the Harris Matrix

Day 10- Stratigraphy, Plan Drawings, and the Harris Matrix

There are a lot of different terms when it comes to stratigraphy, so here we go! Stratigraphy is the process of recording and analysis of site location. Stratification is the physical layering of deposits on a site. Stratigraphy is governed by three principles (for sedimentary deposits), the law of super position, is the order in which sediments are laid down, the principle of continuity, and the principle of original horizontality, ruling that layers will continue in the same pattern of layering over geological breaks (i.e. earthquakes, etc.). It would look like:

Soil A│(break in the earth)│Soil B

Deposits are defined as the assembling and layering down sediment and its inclusions, they can be divided into single events and episodes of deposits. Context (or stratum) is defined by an excavator, may represent a single deposit, may also be arbitrarily defined (since the excavator defines it), and can be known as stratigraphic units. An interface is a boundary between two or more deposits, the soil color, inclusions, or texture change as seen in quadrats (Horizon A, Horizon B), can be seen laid between the top soil and the sub-soil in some instances. If a relationship is found between two non-contiguous contexts, here at Monticello, we refer to it as a correlation, this involves a level of interpretation, and relating vertical texture to past excavations for reference. As we dig through the various matrices of sediments, we often come across non-movable artifacts (non-portable, i.e. boulder or sub-floor pits), these are referred to as features in the context records and archaeological jargon.

As with anything in archaeology, there are types of stratification, used as various ways of defining the horizons. Lithostratigraphy defines horizons through geological/pedological principles, is based on the natural soil formation processes, and applies to all horizons. Biostratigraphy defines the horizon based on presence/absences of life forms, such as fossils, and pollen analysis. Ethnostratigraphy is defined through evidence of cultural activities, such as plowing, or chemical testing for manure use in farming. All of these various forms of stratification are all not mutually exclusive and all of these are used by the archaeologist to date a site (i.e. not just ceramics).

It is the job of the archaeologist then to map these horizons, as the very act of excavation is destruction, it is important to record every detail, through each step of the dig. The goal of mapping the site is to record and show the natural and arbitrary boundaries of the excavation and to differentiate between the two types of interfaces. Quadrats are the arbitrary boundaries and use the mapping notation of line-dot-dash, natural boundaries (cliff, river, or sediment change) are drawn with solid lines to represent separate contexts. These mapping devices are used to illustrate the physical relationships of the site, as well as the stratigraphic relationships. An example of this vigorous record attention can be found in the field, as whenever we close a context in our quadrats, we have to map and record (known as quadrat drawings) the geometric location of each feature (rocks mostly), in order to record each step of the land we dig out, so that future archaeologists can refer to our notes and drawings in the future if need be.

There are various models to follow when plan drawing, there is the single-level plan (“top” plan), the phase plan drawing, and the single context plan. The “top” plan has no discrete boundaries, mostly used in large open excavations, and requires the mapping of each day’s work. The phase plan is more interpretive, placing all things together on one map which are thought to be from the same time period, this model obviously has a more chronological focus. The single context plan is what archaeologists of Monticello use, focusing on each context as a separate quantity, including the natural interfaces between a context and their relationship physically to one another. In order to pull of these descriptions together from the 266 different quadrats dug at Monticello, a device known as a Harris Matrix is used to date the multiple stratigraphic layers, and also to show the chronological sequence of the several dig sites on the mountain. The Harris Matrix represents a form of reverse engineering, structuring the sediments (including features), in conjunction with the artifacts found within the quadrats, and then placing that structure into a chronological chain, with the youngest top soil on top (labeled “A”) and the oldest on the bottom link of the chain, etc. This is an easy way to collect data from a hundred-some plan drawings, descriptions, and artifact finds into one easily interpreted chart. The Harris Matrix is always defines a temporal relationship and is not a fine scale. (below- an example of a Harris Matrix, not relating to Monticello)

Day 9: STPs and Poisson Distributions

Day 9- STPs and Poisson Distributions

The archaeological record is defined by the scatter of artifacts in their matrices near and on the surface of the earth. There are various ways to think about this record, traditionally as the site versus empty space, and thinking of sites as “natural” empirical units. Recently, however, archaeologists have begun to think of sites as a continuum of artifact densities: high to low and to zero density. This is then divided into “site” versus “non-site” occurrences. “Sites” are analytical units, created by researchers for specific purposes. The process of finding archaeological sites requires a process for investigating patterning in the archaeological record at large spatial scales. In the example of Monticello, the entire mountain serves as our site.

One type of survey is called coverage, due to the fact that total coverage of the study area is investigated in its entirety, usually using a single set of methods (e.g. Shovel Test Pits, surface walkover), and is sample based, meaning that an area is divided into multiple sampling units, only some will be fully investigated. The choice of which units is random, systematic, and purposive. There are three dimensions of variations in surveying, spatial samples, subsurface survey, and site survey. Spatial samples are surface surveys (inspections of the ground), which require some decisions as to the amount of survey exposure, spacing of surveyors, and the speed of movement and work to which the excavation takes.  Subsurface surveys dig using subsurface probes, again this require certain decisions, such as the probes spacing, the probe size (Auger holes, Shovel Test Pits, quadrats), or screenings. Site survey designates “sites” in the field, artifacts are provenienced by “site,” this is problematic because site survey is the most common in archaeology, but leaves the site to be openly interpreted. Whereas, in non-site surveying, artifacts are provenienced without regard to whether they occur to “sites,” but are mapped in regards to the STPs (Shovel Test Pits) in which they occur.

At Monticello, we use STPs on 40ft. centers, if an artifact is found, then we move into 20ft. centers, if another artifact is found, we moved down to 5x5 ft. quadrats and screen the dirt with a 1/4 inch mesh screen. The STPs are mapped on the Virginia State Plane for record keeping purposes. The Monticello Plane Survey uses the coverage survey, subsurface survey, and on site surveys. The non-site survey, however, has its own advantages over site surveys. The act of creating “sites” is purpose driven and transparent for non-site surveys, non-site also has the possibility for others to evaluate the results, and the possibility to do it multiple ways. Defining a “site” otherwise gets you as a researcher and archaeologist into a grey area.

Modeling a Subsurface Surveys requires calculating how close the STPs should be, in order to do this the probability of intersecting a site, and the probability of finding one or more artifacts )given that you intersected a site) must be taken into account. In order to model a subsurface survey you must assume “sites” are “non-sites,” the probability that an STP will go into a site (site size and spacing) as well as the probability of finding one or more artifacts given the intersect site. With this the artifact density (mean or variance), screens, and STP diameter are a part of the equation necessary to find this probability. In order to solve for the probability of finding artifacts in STPs, a couple of equations are necessary, which again for math’s sake I will not go into detail about. The equation’s names are the Poisson Distribution, which is used for rare events, and as the mean increases, the Poisson becomes the Gaussian Distribution.

Friday, June 14, 2013

Day 7: James Fort and Williamsburg Field Trip!

Day 7- Field Trip to the James Fort and Williamsburg

This fabulous field trip was originally scheduled for Friday, June 7, but due to the tropical storms, we decided to push it back to Monday in hopes of better weather, because if you haven't noticed it yet, archaeologists can’t dig or view other dig sites in the rain. Of course, it also rained on Monday, but we continued on with our journey ahead of us and learning goals in mind. In reference to Monticello, visiting the James Fort and the Colonial Williamsburg Foundation Archaeology lab was to compare the differences in the soil textures between the Piedmont region (Monticello) and the Coastal Plain region (James Fort, Williamsburg), but also to view their artifacts collections from the sites, and then compare and analyze them with the artifacts found within our own back at Monticello. One primary example is the use of oyster shells as a dating tool in the Coastal Plain (especially Williamsburg), due to their abundance and popularity, and their natural aging records are marked on the interior arches (similar to tree rings), which is similar to the ceramic techniques used to hypothesis an estimated site occupation date.

First stop of the morning was to meet up with Dr. William Kelso, the Director of Research and Interpretation for the Jamestown Rediscovery (M.A. early American history, College of William and Mary, and Ph.D. in Historical Archaeology from Emory University), who was also once a research archaeologist and director of archaeology (1986-1993) at Monticello and began the field school himself during his time with the Jefferson Foundation. Dr. Kelso is also a long-time mentor and friend of Dr. Neiman.

Once we arrived at James Fort, we headed directly to the yard behind the Fort’s church tower, which dates back to 1639. The tower serves as the key to orientating and interpreting the settlement’s physical structures and recreating the surrounding buildings based off of primary documentation from the settlers. The site in the following photos lies behind the 1639 church, away from the James River. At the time of our visit, the Jamestown Field School program was excavating the yard to determine how far the church yard extended after a mid-18th century donation of land, and to evaluate how much fill (human deposited sediment) during the Civil War when the land was used as Fort Pocahontas, which stood adjacent to the seventeenth-century church tower. The photo reveals what the archaeologists believe to be a continuation of the fencing from the original church. 

(The James Fort 1639 church tower remains)

The next photo is the excavation area where "Jane" was found in the last year of excavations. The evidence on Jane's bones proves that during the year of 1609-1610, the settlement suffered heavy starvation issues due to insufficient supplies and trade relationships with the local Virginian Indians. Jane's skulls had significant scratch marks evident of death by cannibalism. At 14 years old, Jane was the victim of her own community's desperation for relief and survival from the starvation which plagued the young British colony. 

(Excavation where "Jane" was found. This would have been the kitchen- located in the center of the James Fort triangulated community)

(From left to right, Dr. Fraser Neiman and Dr. William Kelso discuss the excavation of the kitchen area and how the discovery of Jane occurred and was confirmed through archaeology, historical documentation, and forensic evidence)

("Jane's" skull with evidence of cannibalism: below the right eye socket a series of small, fine cuts from a knife, made while removing the cheek muscle, the back of the skull shows a series of deep chops, these blows fractured the skull along the mid-line, numerous small knife cuts and punctures to the lower jaw reflect attempts to remove tissues from the neck and jaw, left temporal bone shows results of puncture by a small, rectangular tool, as it tried to gain access to the brain, and the most prominent, the four chops to the middle forehead represent a tentative, failed attempt to open the skull)


The next stop on the fieldtrip was to visit the artifact laboratory to meet with the head of the Colonial Williamsburg Foundation's Department of Archaeological Research. 

(Monticello Field School students look over the extensive collection, thanks to the Department of Archaeology at the Colonial Williamsburg Foundation for hosting us and making us feel more than welcome!)

Stay tuned for more exciting updates!!

Wednesday, June 12, 2013

Day 8- Putting Skill on the Map

Day 8: Putting Skill on the Map

Slowly but surely, catching up with the daily blog, for Tuesday’s lecture Dr. Neiman presented a lecture on datums, map projections, and grids. Most people when they think about archaeology would immediately think about finding artifacts in exotic foreign lands, and well, yes that is true, but another major part of archaeology is being able to know a lot about geology. Since we, as archaeologists, spend our time in the dirt, we know that it can hold a great deal of facts or secrets within its many layers, if you just look close enough to find them. Dirt of course, is just one small element on the bigger picture of Earth, so first we need to have a little background in geodesy.

Geodesy is the science of measuring the shapes of the earth. Traditionally in the past, archaeologists used to use grid systems (local grid systems) to set base lines in order to dig, which meant randomly assigning a zero point (0,0- thinking back to basic geometry). Today however, thanks to the wonderful advances in technology we have the satellite and GPS (Global Positioning Satellite), the once used arbitrary grids formed by archaeologists have been swapped for Real Earth Grid Systems.

Isaac Newton was the first to state the earth was not exactly circular, but rather that it formed an ellipsoid. In the nineteenth and twentieth centuries, different ellipsoid models were developed for different parts of the world in order to make map estimate plan tangent to the curved surface of the earth. A level plane is perpendicular to the local direction of gravity, which varies by very small degrees in different regions, and how specifically gravity varies is described by the geoid.  The geoid is the level at which gravity is sea level. Again, with the technology of satellites, measurements of modern ellipsoids are able to fit global “bumps” in the geoid, making it applicable for the entire world to use. This is done by taking the gravametric center of the earth with satellite technology, and the global geoid used today is called World Geodetic System-84 (WGS84, from 1984).

When discussing datums is it important to keep in mind that latitude and longitude are major and minor axes defined on an ellipsoid fit locally or globally to the geoid (WGS84). In turn, the poles and the equator can be defined as well. Poles are the axis of the revolution of the ellipsoid and the equator is the mid-way between the poles spanning the widest part of the ellipsoid. Together, these define latitude as a natural measurement. Longitude is defined as arbitrary, it has no natural starting place on Earth’s surface- the zero degree point is the Greenwich Meridian in England. The place where latitudes and longitudes are actually located on the ground is termed the “Geodetic Datum.” The Geodetic Datum is a network of controlled points on the ground whose locations are given in terms of estimated latitude and longitude. In order to create a geodetic datum you have to specify an ellipsoidal path on the model of the Earth, and create a network of carefully surveyed locations estimating the latitude and longitude. With WGS84, newer datums are geocentric, meaning it is useful anywhere, whereas the older datums were based on locally ellipsoids, isolating their use. In North America, the North American Datum of 1983 is our geocentric reference ellipsoid locally for our continent, and the World Geodetic Survey of 1984 (created by Doppler satellite) serves as the geocentric reference ellipsoid for the entire world.  

These datums are most commonly used for map projections, which is the process of transferring points from the surface of the ellipsoid to a plane. All map projections created some distortion- some are better than others. Which projection is best, depends on the shape of the area you are trying to map (map surface does not equal ellipsoid surface). There are three projections surfaces: cylindrical, conic, and Planar (Azimuthal) and three projection orientations: equatorial, transverse, and oblique. As well as two different kinds of possible contact: tangent, being in contact at a single point along a line, and secant, cutting, or intersecting the surface.

Here at Monticello, there are two main projections we need to know: the Lambert Conformal Conic and the Transverse Mercator Projection. 

The Lambert conformal conic, means that a cone wrapped around the earth, with the projection surface touching the ellipsoid surface along two standard parallels, and this projection has the least amount of distortion runs along the east and west parallels. The Transverse Mercator Projection means that a cylindrical projection surface touches the ellipsoid surface along one central north and south meridian, and the least amount of distortion is along the north/south parallel. Within the United States, the U.S. State Plane Coordination System is used as an underlying projection, utilizing the Lambert Conformal Conic for states with large east/west areas, and the Transverse Mercator for the states with large north/south areas. On an even larger scale (again), the Universal Transverse Mercator Coordination System (UTM) is the underlying projection for the world.

Now, how does all these datums and map projections relate to archaeology? I’m about to show you. The bottom line is, you need to know your map projections and datums so that you can know what grid your site is on, in order to fully, and accurately record your dig. In the case of Monticello, it is also useful to know that the local grid system (VSP- Virginia State Plane) will be easy for your archaeological research design, than using the global grid (GPS). Officially, Monticello is under the N. Am. Datum of ’83, the Lambert Conformal Conic Projection, and the Virginia State Plane System. So the next time you look at a map- try to test your new geodesy, datum, and map projection skills!

P.S. I will be posting the blog from Monday's fieldtrip to Williamsburg and James Fort by Friday night- with pictures!