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TEACHER'S CORNER: animal tunneled down through a site,, causing artifacts buried above to fall RELATIVE DATING TECHNIQUES to lower levels. Natural processes like
IN ARCHEOLOGY frost heaving, erosion v and the down- The question. How old is it?, is slope movement of soils in colder basic to the science of archaeology. climates (solifluction) can alter the Dating methods, such as radiocarbon original context in which the artifacts dating, dendrochronology or tree-ring were deposited. dating, and potassium-argon dating, that may furnish an absolute date for Stratigraphic levels can be an archaeological site, are a horizontal as well as vertical. On contribution of the physical and the beaches, where the configuration of the natural sciences. But absolute dating shoreline has changed through time y the methods are not always useful; the earliest site may be inland, the later particular circumstances to which they site closest to shore. The stratigraph- apply do not exist at every site. In ic levels would then be spatially such cases, archaeologists may employ horizontal, conforming to the changing relative dating techniques. Relative coastline. Horizontal stratigraphy may dating places assemblages of artifacts also occur when a later culture settles in time, in relation to [artifact] next to an earlier abandoned site, types similar in form and function. thereby appearing to be contemporary to the older site. Despite problems of The classroom exercises below will interpretation, stratigraphy is a
focus on stratigraphy and seriation , powerful archaeological tool in un- dating techniques used by locking the mysteries of past lifeways. archaeologists to establish a relative chronology. Exercises :
I. Stratigraphy or the Law of 1 Ask the students to think of ways Superposition that the vertical sequence of newspapers could be disturbed. (If the Stratigraphy can be described as a newspapers were not dated, the "layer cake" type arrangement of chronological sequence could probably
deposits called strata , with the older still be deduced from their content.) layer beneath the latest. This technique helps the archaeologist arrange the 2 Using the example of the stack of site in a vertical temporal sequence, newspapers, ask the students how they which may then be compared to sites of might apply relative dating using the similar age or type. You might ask concept of horizontal stratigraphy. students to picture a pile of news- papers that have been stacked every day 3. There are many possibilities for for a week. The oldest newspaper will a theoretical sequence, once the be on the bottom, the remainder stacked students are familiar with the material in relative chronological order from culture and history of groups inhabit- the oldest to the latest edition. This ing the United States at various times. is the concept of stratigraphy—or the Better yet, use the chronology Law of Superposition. developed for your local area. The students may then generate a "time Stratigraphic sequences in the line," interpreting the ways in which field, however, are sometimes past peoples may have used the unreliable. Suppose the inhabitants of artifacts at their disposal in their a previous site dug a large hole. The daily lives. top of the heap of excavated dirt would date the oldest. Or perhaps a burrowing .
Have your class develop a poster They make pottery, which is not easily showing a theoretical stratigraphic portable, as well as decorative items. deposit, or archeological sequence. They have access to a regular food Then ask them to analyze the cultural source,- as the grinding equipment materials to deduce what the lives of shows, but probably still also hunt for the people of that time were like. wild game Below is an example of a possible sequence that could be illustrated on a Level III (latest): pictures of a pipe poster. stem (which can be assigned a date of 1794 by its diameter); a coin dated Level I (earliest): pictures of 1802; a bullet casing; a few grains of f ireblackened rocks in a rough circle corn; the skeletal remains of a horse; suggesting a hearth; scattered stone a metal coffee pot lid. What can be tools; and scattered animal bones and said of these people? What cannot be fruit pits. These artifacts suggest a inferred from this level? The coin is people who hunt and gather for a significant because it provides the living; who own few material earliest potential date of the site. possessions , suggesting mobility; and The coin was made in 1802 y but could who have mastered the use of fire and have been dropped any time after that tool making. date, as the pipe stem must have been dropped later than its date of
Level II (middle) : pictures of sherds manufacture. This concept called the (broken pieces) of decorated pottery; a terminus post quem (the date after mortar and pestle for grinding grain; which) is of particular importance to scattered beads and carved figures; archaeologists dealing with the post holes (shown as a regularly historic period. patterned darkened areas of soil) for a dwelling; scattered bones of wild game. Your local archeologist may be able to These artifacts suggest people who are furnish suitable materials, or the settled, at least part of the time. sequences in the publications listed ,
below may be used for illustration. The that has been called the "battleship time line generated by your students curve." An item is introduced, it grows will introduce them to the important in popularity, then its use begins to concept of stratigraphy, as well as to wane as it is replaced by another form. the goal of archaeology: to reconstruct Certain types of artifacts have been past lifeways and place them in a identified as particularly useful chronological framework in order to temporal markers y for example, better understand the present. gravestones, projectile points,, lamps Y pottery sherds. 4. Archaeologists may date deposits on the basis of the newest artifact found Before being able to interpret in the level. To illustrate this materials found at a site, an concept, collect a handful of coins of archaeologist faces the task of sorting varying dates. Which is the oldest? the artifacts into manageable units for Which is the latest? If they were all analysis. This is frequently a buried together, what date could be difficult task. Sorting is usually placed on the level in which they were based on form and function. What does found? The answer is that we can only it look like? What is it made of? Is it say that the coins were deposited decorated in any way? Have you ever sometime after the date of the newest seen it before? coin,
Exercises : 5. For younger students Y the concept of stratigraphy may be reinforced by 1 . To acquaint your students with the gluing the pictures of artifacts to problems faced by archaeologists in cardboard and cutting them up as one determining the form and use of an would make a puzzle. These could then object, ask each one to bring in an be scattered over layers made of unusual item or two, whose function may crumbled tissue paper, to be not be well known. Possible objects "excavated" and "mapped" in levels by are: old kitchen implements, personal the class. A grid of rubber bands or items [shaving brushy buttonhook] string may be placed over the "site" to parts of toys, travel souvenirsy and aid in the accurate mapping of the natural objects such as unusual rocks. artifacts . Students may be divided into teams of excavators and mappers with as Ask the students to exchange their many "sites" as feasible. The students items with others in the class to guess then could make a time line based on their use. Then ask the students to the interpretation of their finds. arrange them in sets according to distinctive characteristics. The kinds of questions they should ask are: Is it II. Seriation made of woody paper, cloth, metal, pottery? Is it large or small? Is it
When a stratigraphic sequence is for personal care, decoration y or lacking, another relative dating amusement, or does it have a technique known as seriation may be utilitarian purpose? applied. This technique dates a site based on the relative frequency of How was it made? Were the materials types of artifacts whose dates of use used in its manufacture from the local or manufacture are known. The basic area or from far away? Where was the assumption underlying seriation is that object itself made? How did it get the popularity of culturally produced here? Who made ity a specialized items [such as clay pipes or obelisk craftsman or an ordinary member of the gravestone markers in America] varies society? The categories for classifica- through time, with a frequency pattern tion will be suggested by the objects ) . , .
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in the assemblage. Are there any patterns apparent in the objects the students have brought to class? Is any item of a greater frequency?
2 . Ask the students what they can deduce about the people who use the objects. This exercise will introduce students to the concept of deducing the lifeways of people from the artifacts of material culture, which were used in everyday activities
For further information :
James Deetz. Invitation to Archaeology . New York: The Natural History Press 1967.
David Hurst Thomas. Archaeology . New York: Holt, Rinehart, and Winston, 1979. (more technical)
Robert L. Humphrey and Mary Elizabeth Chambers. Ancient Washington; American Indian Cultures of the Potomac Valley. Washington, DC: George Washington University, 1977.
( local study containing cultural sequence of eastern U.S.)
Naturalist Center , National Museum of Natural History, 10th & Constitution Ave., N.W., Washington, DC 20560; (202) 357-2804. (Reference materials, self study guides on Indian pottery and stone artifacts, and on human skeletal materials.
Public Information Office , Department of Anthropology, Smithsonian Institu- tion, Washington, DC 20560. ("Local Archeology Resource Packet: District of Columbia,. Maryland, and Virginia"; teacher bibliography and classroom materials on archeology)
Cathy Griggs George Washington University Washington, DC