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Archaeology and Science

 Raji Sinha

Academic setting

This unit will be used at Rio Grande High School (RGHS).  I am designing this unit to be used for tenth to twelfth grade students.  The typical class size will be twenty five to thirty students.  RGHS serves a predominately low-income, Hispanic, semi-rural population (about 2000 to 2500 students).

Goals of this Unit

The goal of this unit is to introduce to students a general knowledge and awareness of Archaeology and the scientific methods used to analyze the past.  Many of my students have a problem of understanding how our past tells the story of present human culture and development of civilization.  How we can have some idea to make a better future if we understand our past and take care of our present.  This paper describes some scientific methods used in Archaeology to study the past. My intention is to teach the students about the modern technology available and how much the technology has contributed in analyzing the archaeology. Although these scientific methods are not available in the normal classroom, I tried my best to introduce simple lesson plans which includes simple tools which are available in the high school class room. 

Narrative 

What is Archaeology?

Archaeology is the study of the material remains and environmental effects of human behavior: evidence which can range from buried cities to microscopic organisms and covers all periods from the origins of humans millions of years ago to the remains of 20th and 21st century industry and warfare. It provides us with the only source of information about many aspects of our development. Milestones such as the beginning of agriculture, the origin of towns, or the discovery of metals, can only be understood through the examination of physical evidence. Archaeology also provides essential information for periods of the past for which written records survive. Archaeology links with many subjects, including geography, history, social sciences, math, physics, biology, chemistry, art, religion, and technology.

History of Archaeology 

The discipline had its origins in early efforts to collect artistic materials of extinct groups, an endeavor that can be traced back to the 15th cent. in Italy when growing interest in ancient Greece inspired the excavation of Greek sculpture. In the 18th cent. the progress of Greek and Roman archaeology was advanced by Johann Winckelmann and Ennio Visconti and by excavations at Herculaneum and Pompeii; in the 19th cent., by the acquisition of the Elgin Marbles. The study of ancient cultures in the Aegean region was stimulated by the excavations of Heinrich Schliemann at Troy, and of Arthur Evans at Crete. The work of Martin Nilsson, Alan Wace, and John Pendlebury was also significant in this area, and the decipherment of the Minoan script by Michael Ventris raised new speculations about the early Aegean cultures.

     The foundations of Egyptology, a prolific branch of classical archaeology because of the wealth of material preserved in the dry Egyptian climate, were laid by the recovery of the Rosetta stone (Rosetta) and the work of French scholars who accompanied Napoleon Bonaparte to Egypt. Investigations that have reconstructed the lives and arts of elite segments of ancient Egyptian society and rewritten Egyptian history were carried on in the 19th cent. by Karl Lepsius, Auguste Mariette, and Gaston Maspero, and in the 19th and 20th cent. by W. M. Flinders Petrie, James Breasted, and others.

     Interest in the Middle East was stimulated by the work of Edward Robinson (1794–1863) on the geography of the Bible and by the decipherment of a cuneiform inscription of Darius I, which was copied (1835) by Henry Rawlinson from the Behistun rock in Iran. Archaeology in Mesopotamia was notably advanced in the 19th cent. by Jules Oppert, Paul Botta, and Austen Layard and in the 20th cent. by Charles Woolley, Henri Frankfort, and Seton Lloyd. The discovery of the Dead Sea Scrolls, beginning in 1947, aroused new interest in biblical studies (biblical archaeology).

     Interest in New World complex societies was stimulated by the publication by John Stephens of an account of his travels (1839) in Central America, which excited the interest of archaeologists in the Maya. In the 19th cent. studies began of the Toltec and the Aztec in Mexico and of the Inca in South America. In 1926 the discovery of human cultural remains associated with extinct fauna near Folsom, N.Mex. (Folsom culture), established the substantial depth of prehistory for the New World (please see more references in documentation). 

Morden Archaeology

In contrast to the antiquarianism of classical archaeology, anthropological archaeology today is concerned with culture history (i.e., the chronology of events and cultural traditions) and the explanation of cultural processes. A variety of different dating techniques, both relative (e.g., stratigraphy) and absolute (e.g., radiocarbon, obsidian hydration, potassium-argon), are used to place events in time. Attempts at explaining evolutionary processes underlying prehistoric remains began with the conclusion advanced in 1832 by the Danish archaeologist Christian Thomsen that cultures may be divided into stages of progress based on the principal materials used for weapons and implements. His three-age theory (the Stone Age, Bronze Age, and Iron Age) was essentially based on prehistoric materials from Scandinavia and France.

     Concerted investigations began in the mid-19th cent. with the stratigraphic excavation of such remains as the lake dwelling, barrow, and kitchen midden. At first the sequences of culture change uncovered in Western Europe were generalized to include all of world history, but improved techniques of field excavation and the expansion of archaeological discoveries in Africa, Asia, and the Americas challenged the universality of rigid classifications. Technological traditions ceased to be regarded as inevitable concomitants of specific cultural stages.

     Later interpretations of prehistoric human life emphasize cultural responses to changing demographic and environmental conditions (see ecology). Thus the Paleolithic, Mesolithic, and Neolithic periods are evaluated in terms of subsistence technologies, and explanations are sought for the causes underlying these transitions. Advances in the recovery and analysis of botanical remains have allowed investigators to model changes in the prehistoric environment with increasing precision, improving the accuracy of such explanations. Paleobotany, the analysis of ancient plant remains, and ethnobotany, the study of the cultural utilization of plants, therefore play a vital role in modern archaeology.

     Faunal analysis, the recovery and analysis of animal remains such as bone, also plays an important part in the study of prehistoric ecology and subsistence patterns. The careful analysis of botanical and faunal material, combined with advances in the analysis of genetic material, have led to the detailed understanding of the process of the domestication of plants and animals in both the Old and New World. Contemporary archaeologists are also concerned with the emergence of various forms of complex social organization, including chiefdoms, class stratification, and states. Among the most important work done in the mid-20th cent. was that of Louis and Mary Leakey, who located the skeletal remains of humans in East Africa dating back 1.7 million years (human evolution). In recent years, a number of archaeologists have turned from traditional concerns and have made efforts to reconstruct ideological elements of extinct cultures.

     Modern museums with valuable collections include the Metropolitan Museum and the American Museum of Natural History in New York City; the British Museum; the Louvre; national museums in Denmark, Norway, and Sweden, rich in remains of the Iron Age; the Vatican and Capitoline museums, Rome; collections from Pompeii and Herculaneum at Naples, Italy; and museums in Athens, Cairo, and Jerusalem. Many universities have established schools and museums of archaeology. Organizations such as the National Science Foundation, the Smithsonian Institution, and the National Geographic Society in the United States promote archaeological studies (please see more references in documentation).

Methods of Analysis

Now a, days there are many methods available to do Archaeological analysis.  Some of them are as follows: Archaeometry, Ceramic Petrology, Dating Techniques, Determining Ancient Measurements from Structures, Dual Energy X-Ray Absorptiometry (DXA), Taphonomy and Archaeozoology, Artifact, Geophysical Methods and Human Osteology etc.  In this paper I will be briefly describing only five methods.

A). Artifacts

What is an Artifact?

An Artifact is any object that was made by or altered by humans for some purpose or task.

How do Archaeologists use Artifact?

Archaeologists use artifacts to teach us about the ways that people lived in the past. The artifacts teach us about the types of food people were eating and how they were preparing it, trade and travel practices, hunting practices, their homes and furniture, behavior patterns, etc. Without the artifacts, most archaeological sites would teach us very little about the past.

Are all artifacts man-made?

An artifact is defined as something that is made by humans. Typically found artifacts are made out of things like glass, pottery, various metals, and sometimes bone (such as bone buttons). Also found some prehistoric Native American artifacts made out of stone (such as the projectile points). Things that are natural, such as unmodified bone or rocks, are not really considered artifacts, but are often called "ecofacts". Of course, depending on where they are found, even the "ecofacts" can often tell us about how our ancestors lived.

Where to find the Artifact?

A lot of times, artifacts are found by archaeologists while they dig, or during screening of dirt excavated from sites. Sometimes we even find artifacts right on top of the ground! Once an artifact is discovered, archaeologists know that is very important to make sure we record exactly where it was found. The locations of artifacts can help us determine if we are on an actual site. Or, if we have already been digging at a site, the locations of artifacts may help us figure out how different parts of a site were used (for example, was the area of the site used as a house, a barn, or a trash pit) or sometimes even the approximate age of the site.

     There are a lot of natural and human-made ways in which sites and artifacts become buried or exposed. Sites can be buried by things like natural decay of vegetation, floods, and volcanic eruptions. Sites can be uncovered by wind action, freeze/thaw action, or even something as simple as a farmer plowing a field. It is worth noting that some sites never are buried. They are located in areas where little soil development occurs or where there are no other natural or human-made ways that could bury the site.

Where would Archaeologists digs take place?

An Archaeologists dig could potentially take place anywhere where human beings may have lived, worked, created, played, ate, etc. in the past. What do you think archaeologists in the future would learn about our present day society by looking at the everyday objects we use today?

What tool archaeologists use?

Archaeologists use a lot of different kind of tools in their work; sometimes the kinds of tools used depends on the kind of work we are doing. Of  they, use shovels, buckets, and screens, but also use trowels, measuring tapes, brushes, hoes, plastic bags to preserve etc.

Are kids allowed on site? How would one can obtain access?

Typically, many archaeological sites that are undergoing major excavation, will hold "open-house"-type days where the public can come and see the site and talk with archaeologists while they are actually working. Of course, a lot depends on whether or not the site can be easily reached. Also, not all sites hold advertised public open-house days; and, in this case (principally for safety's sake), it is usually a very good idea to call ahead to the institution doing the dig to see if the site is open to visits and/or to make an appointment with the site's director. In the United States, almost every state has an "Archaeology Month" where the public is invited to attend special lectures or classes, visit sites, and even participate in ongoing excavations.

             To learn about Artifact one should visit many placeless.  I have described some sites of New Mexico which might be good to visit and see the Artifact (see documentation, Archaeological Sites of the Southwest).

B) Radio carbon dating  

What is Carbon Dating?

Archaeological dating methods are used to understand the history of earth; how life has spread and which life forms have existed. Archaeological findings reveal e.g. changes in climate, which enable scientists to predict future changes. The findings also visualize the development of modern man; technique, way of life, culture, eating habits. The possibility of establishing dates of archaeological findings is essential to the archaeologists work. Unfortunately, there is no standardized method that ranges over unlimited time or that can be applied on any material. The archeologists must therefore combine different methods to achieve optimal results. The most common methods are introduced in this paper. My aim is to survey the chemical part of archaeological dating methods.

An overview of different chemical methods for Archaeological dating purpose 

Method	Matter	Time range
Radiocarbon	organic matter	50 000-80 000 years
Thermoluminescence	Pottery	500 000 years
Amino acid	Organic matter	1 000 000 years
Dentrochronology	Wooden objects	-

Reference to Table: The Cambridge encyclopedia of archeology, Andrew Sherratt, Cambridge U.P: 1980, Arkeologi, Kristina Ambrosiani, Gamleby: arkeo-förl. 1989

What is the method?

The American chemist, Willard F. Libby at the University of Chicago developed the radiocarbon method, (C 14) in the 50 ´s for which he received the Nobel Prize in chemistry in 1960. The method revolutionized scientists` abilities to date the past. Today, there are over 130 radiocarbon dating laboratories around the world. The C14 method has been and continues to be applied and used in many, many different fields including hydrology, atmospheric science, oceanography, geology, archaeology and biomedicine. Although it was almost 50 years since the radiocarbon method was first introduced, it is still among the most commonly used method. Its ascendance is due to these simple but never the less important properties:

ˇ        It can be applied on many different materials, for example bones, wood and textiles.

ˇ        It covers a range of time which corresponds to the entire development of modern man, that is about 50 000 years.

ˇ        It can be applied anywhere in the world.

    The principle:

The principle of the radiocarbon method is based on fact that the earth is constantly subjected to cosmic radiation. These high-energy particles pierce the upper layers of the atmosphere and cause several nuclear reactions, which causes free neutrons. When these free neutrons interact with nitrogen atom, unstable carbon isotopes are formed.

₇ ¹⁴N + ₀ ¹n --> ₆ ¹⁴C + ₁ ¹H

As most elements in nature, carbon exists in more than one isotopic form. The isotopes 12C and 13C are stable, but the third isotope 14C is radioactively unstable, that means it is constantly decaying. All carbon isotopes have the same number of protons, but different numbers of neutrons and different masses. The presence of Radiocarbon (14C) in nature is very rare. Only 0,000 000 00010 %. Whereas the 12 C has 98,89 % and 13C has 1,11 %. The carbon isotopes are oxidized by the oxygen atoms in the air and CO2 is formed. 14 6 C + 2O ? CO2 The carbon dioxide enters the ecological system by the photosynthesis and become distributed in the atmosphere, the ocean and the biosphere. A certain level of carbon isotope is established in all living organisms this way.

         As long as the organism is alive its ratio of 14 C /12 C in the molecules is the same as in the atmosphere. But when it dies, the ratio of radiocarbon can no longer be maintained, and the level of 14 C starts to decrease, according to its radioactively half- life. (The level of 12 C will be the same because it is stable.) The formula when 14C decompose is: 14 0 14 6 C ? -1 e + 7 N The half-life for radiocarbon is 5730 years. After one half-life, half of the atoms in a sample are still there. After two half-lives a quarter of the original sample is left, and so on. When the amount of radiocarbon in a sample is measured and the radiocarbon’s disintegration rate is known, then the sample’s age can be calculated. After 10 half-lives, there is a very small amount of radiocarbon present in a sample. At about 50 – 80 000 years, the limit of the technique is reached. (Beyond this time, other radiometric techniques must be used for dating.).

What are the objects that can be dated using the Radiocarbon method?

Because carbon is very common on Earth, there are a lot of different types of materials, which scientists can date. Here are some examples: Hair, bone, leather, soil, bird eggshell, blood residues, fish and insect remains, iron, wall painting and rock art work, etc.

Famous things that have been Radiocarbon dated

The Iceman is a very famous frozen body found in northern Italy in 1991. Samples of his grass boot, leather, hair and bones were dated. The results showed that he lived almost 5500 years ago. One of the most controversial examples of the use of radiocarbon dating was the analysis of the Turin Shroud, the supposed burial cloth of Jesus. The results were very consistent and showed the shroud dated between 1260-1390 AD. This fits closely with its first appearance in the historical record and suggests strongly that this is a medieval artifact, rather than a genuine 2000-years-old burial cloth.

What kind of problems one will face with Radiocarbon dating method

Only organic matter can be dated by this method. It doesn’t work on fossils for example.

ˇ        Radiocarbon dating only works on relatively recent specimens, even if recent technological advances have increased the time depth.

ˇ          There are many opportunities for carbon contamination. If plant roots grow into a specimen they bring in “young” carbon. The result of radiocarbon dating will be a younger date than is actually true.

    Technique:        

The Geiger Counter  

Using a Geiger counter is the most common method of measuring radioactive levels. It makes the particles from the radioactive decay process produce ions when it passes through matter. The probe (see appendix 1) can be filled with argon gas, and when the high-energy particles passes through it, the gas will be ionised according to the formula: Ar (g) ? Ar+(g) + e- When this happens, there will be a momentary current to flow, which can be measured by electronic equipment, and the number of events can be counted. In this way can the level of a radiocarbon sample be determined. One negative thing with this method is that it requires a rather large amount of purified carbon, which means that as much as 10-20 g of wood or charcoal, and 100-200 g of bone is required from the original sample.

Mass Spectrometer  

This method only requires 10-3 g of pure carbon. The carbon atoms are ionized, and the particles are accelerated into an electric field. Their course will be bent by the magnetic field. The heavier particles are separated from the lighter particles and they can be counted separately. A detector can determine the masses of the different particles, and because the atomic mass of radiocarbon is known one can calculate the ratio of 14C/12C in the sample.

Amino Acid Dating  

The amino acid method is useful when the age of an organic matter is to be determined. The range of the method is 1 million years, which makes it practical when the radiocarbon method is no longer useful.

The principle

The method is based on that there are certain types of amino acids that exist in two alternative structural forms. Their chemical composition is identical but the atoms arrangement is reversed in one of the forms. They are called enantiomers and the two different forms are called L (laveo-) and D (dextro-) form. In living systems the L-form is synthesized, thus these L-forms undergo a slow transformation and change to D-form. The process is called racemization. This process is measurable during a lifetime, which has made it possible to gauge the rate at which bone undergoes the process. When a bone is examined, the extent of the razemization is measured and compared to the known rate of the process in bone. With this information, the age of the bone can be determined.

Dendrochronology

The science of dendrochronology is the oldest and the most accurate of all methods. The uncertainty lies within only one year. It is not much if it is compared to the radiocarbon method which uncertainty lies within 150 years.

The principle  

The dating is based on that trees create annual growth rings. For example when a tree is cut down, its age can be determined by counting its rings. The rings also tell the archaeologists if the years have been good or bad, depending on if the rings are thick or thin. An old oak can be 200 or 300 years old and that can be the base for a growth ring timetable. To reach further back in time, wood pieces from wooden houses or boats can be patched up to form a schedule that covers a longer period. When you have a sample without a date you can just compare it to the schedule and find a match.

Thermoluminescent

This method is limited to dating pottery, but considering that clay items are one of the most common findings, this method is of great value to the archaeologist’s work.

Clay contains quartz crystals which are thermoluminescent (they give off light) when heated. When a sample lies buried in earth for many centuries it is exposed to natural radioactivity. The lettice of the crystal structure has defects or imperfections where electrons are missing. The natural surrounding radiation contains free electrons, which fill these gaps. It takes about half a million years to fill all the structural gaps. This is the methods time limit.

         When electrons are stored this way, energy gets transferred into the crystal structure. If the sample is allowed to rest in the earth at the same temperature, the electrons will remain trapped in the gaps for eternity. But if the clay is heated to 500 Celsius degrees, the energy is immediately removed. When the energy flows out, the electrons are disengaged and emit glowing light. The more radiation stored in the sample, the more intensive light is emitted. There are three steps in the process of determining age:

ˇ        The intensity of the light emitted is measured.

ˇ        The light intensity is related to radiation dose by irradiating the sample in the laboratory.

ˇ        The yearly dose of radiation that the object has been exposed to is determined.

The age can now be calculated by the Age equation:
                      Age = (Accumulated radiation dose/ (radiation dose per year).

The Clock Resting Event   

When a sample is heated and the energy flows out as light, the intensity determines the time since the object was last deprived of light. That was when the object was manufactured. This point is called the “clock resetting event”. New radioactivity then starts to build up inside the object (please see references for Radio Carbon Dating in the documentation).

C ) Geophysical Methods in Archaeology

Introduction

World war on brought the discovery that photographs behind enemy lines taken from airplanes could be of great value in warfare. Not longer after this, observers taking random photographs from the air over rural England noticed that traces of old Roman walls, forts and roads could be seen on aerial photographs but otherwise went unnoticed under cornfields and pastures when archaeologists wandered about the countryside on foot. Terrain photos from captive balloons had been made even earlier (1860) but it was only in the 1930's and 40's that archaeologists began to take advantage of photos from the air over archaeological sites. Today, of course, stereo-pair color and color infra-red film photographs (or even the newer multi-spectral imaging methods) from the air, are the place to begin in mapping and understanding an archaelogically interesting area.

         In addition to highly evolved aerial photography, airborne and satellite multi- spectral imaging instruments, good ground based geophysical instruments began to be commercially available in the 30's taking advantage of various physical phenomena. Some basic geophysical methods include the following: (1) Seismic Reflection & Refraction, (2) Gravity, (3) Magnetics, (4) Electrical, and (5) Radioactivity. Method (1) is commonly used in oil exploration, engineering geology, and regional geology studies. The gravity method (2) is especially useful in oil exploration. Methods (3) and (4) find common application in mineral exploration, oil exploration, and regional geology studies. Finally radioactive methods are used in exploration for radioactive minerals.

Technique:

Metal Detectors  

A wide variety of "metal detectors" are commercially available today; they have the advantage of being easy to use and most cost only a few hundred dollars. The larger the search coil, the deeper the penetration; however coins and small metal objects can be detected only a few inches deep and very large metal objects only to depths of a few feet. Non-metal objects are not detected. Some areas are too "noisy" for metal detectors. "Noise" can originate from power lines, or from obscuring signals caused by nearby parked cars, scattered nails, re-bar or metallic litter at the site. Highly mineralized areas are difficult to work in, and certain rocks such as iron-rich basalt can be troublesome for metal detector work.

     Metal detectors are active" instruments. A battery-powered transmitter in the unit radiates a relatively low-frequency alternating current signal into the ground by means of a transmitting coil. If the signal from the transmitter encounters any type of conducting metal or mineral in the ground an induced current flows in the subsurface target. This induced current then re-radiates a weak signal back to the surface. The latter signal is out-of-phase with the transmitted signal and thus is easily detected by a receiving coil. Modern metal detectors have circuitry for carefully balancing out any direct signal leakage between transmitter and receiver coils and for discriminating between large and small, shallow or deep, and ferrous or non-ferrous metals.

     The simpler instruments of this type are useful for "coin shooting" at old ghost town sites, or archaeological sites (on land or under the sea), and for locating gold or silver deposits within a quartz vein in a lode mine. Small objects such as coins usually must lie within a few inches to a foot of the surface to be detected by metal detectors.
The sensitivity of metal detectors is a steep function of the coil diameter, however with large coils and ample transmitter power larger metal objects can be located to depths of 10 or 15 feet using metal detectors. Claims for detection at greater depths as well as identification of metals by type are suspect.

Ground Penetrating (GPR)   

Radars designed for probing into the earth typically operate from 30 to 300 MHz-the frequency being determined by the length of the dipole antennas used. It is necessary to use relatively low frequencies because the earth almost always is a good absorber of radar waves. Unfortunately, low frequencies imply long probing wavelengths and long wavelengths imply low resolution. A very short pulse is used allowing accurate measurement of depth to the target, however the antenna beam is very broad (90-120 degrees usually) and can not easily be narrowed because the antennas become too big and bulky.
    
        Very often GPRs are mounted on a small wheeled cart which is hand towed across the area of interest, that is, if the search area is reasonably flat and relatively free of brush and boulders. The echoes are displayed in a continuous strip oscilloscope false color record for ease of interpreting results. In recent years the state of the art in GPR technology has been greatly improved by computer signal processing methods, since the performance of these radars is almost always "clutter limited." Clutter signals are unwanted reflections, off-axis echoes, and multiple scattering echoes. These signals obscure the target of interest under bands of signals but in many cases digital processing improves radar performance by many orders of magnitude.
    
        When cart-mounted radar can be used, an experienced operator can often traversing large areas of surface at a site in a single day. The radar output can be recorded on a standard home video tape for archiving and detailed study, ant also printed out on strip-chart paper for immediate on site analysis. GPRs are usually limited not only by clutter but also by attenuation of the radar signal in the soil. This is most severe in clay soils and damp soils where the salt content is high. The depth of penetration at some sites may be less than 1 foot, or under favorable conditions, many tens of feet or even hundreds of feet. Commercial cart GPRs are priced from about $18,000 to $40,000 and operator training and experience is necessary to interpret the records.
    
          Very often cart radars can not be used because of rugged surface terrain. Or perhaps the area to be explored is underground---inside a tunnel or cistern or along a confined area such as a hillside. Portable individual transmitting and receiving dipoles are useful in such cases. But the data must now be recorded point by point, usually by taking Polaroid photos. Targets of interest can be triangulated and mapped if these targets can be viewed from various aspect angles. Portable GPRs are well suited for discovering cavities and voids, and when soil attenuation values are low they can detect caves, tombs, or chambers one hundred feet or more in depth. Interpretation of GPR records of all types is unusually difficult requiring operator skill and experience for satisfactory results.

Magnetometery

The earth's magnetic field is slightly disturbed by some kinds of archaeological anomalies such as fired clay pottery. The magnetic signals associated with archaeological features are very small and easily obscured by trash metals, power lines, nearby automobiles, and the like. Magnetometers are most suited for remote, isolated sites away from modern buildings and debris. Magnetometers cost from about $1500 to $10,000 and can be used in pairs (a "differential magnetometer" to subtract out all but the wanted signals. Modern magnetometers are sensitive to field changes of about 1 gamma-the earth's weak magnetic field intensity is of the order of 50,000 gammas. Magnetometry has been successfully used to located imported stone at some well-known archaeological sites. Fired mud brick has a reasonably high magnetic anomaly and of course ferrous materials such as one might expect at an Iron-Age or later site, give rise to very large magnetic anomalies.

Microgravity

Gravity is one of the weakest of all forces found in nature. Yet, the earth's gravity field is very slightly altered by such features as subsurface voids or caves. Suitable gravity meters, known as "microgravimeters" cost of the order of $50,000 and require a very experienced trained operator. Point by point measurements must be made, which may be time consuming. The data must be carefully corrected for such things as surface topography and diurnally varying "earth tides." For these reasons gravity surveys have been little used in archaeology to date.

Ariel Photography and Imagery     

Conventional aerial (stereo-pair) photos of a site are very useful, as has been suggested, since outlines and features not visible from the ground frequently show up in aerial photos. Thermal infra-red (IR) imagery requires a scanner, usually cooled by liquid nitrogen, (instrument cost $15,000 to 50,000), but surface temperature differences of a small fraction of one degree can be measured. At night radiation cooling of the ground is not uniform if there are subsurface features that impede or enhance heat flow. In additional to diurnal heating and cooling, seasonal heat flow temperature changes can often be detected providing information on deeper archaeological anomalies.

     Heat flow through rock and soil is very slow---rock is an excellent heat insulator---so infra- red measurements give information about temperatures near the surface, not about temperatures deep within the earth. In spite of the limitations, false-color images showing temperature contours can thus provide interesting clues for the archaeologist at some sites, especially if such measurements can be made carefully at periodic intervals through an entire year. The Temple Mount in Jerusalem is an ideal site for on-going thermal infra-red imaging studies and Tuvia Sagiv, an architect from Tel Aviv, has already obtained some fascinating thermal IR images of the Temple Mount area. These can all be done from a distance or from the air.

General Comments   

If an archaeological site is complex and important, likely to be excavated for many field seasons, geophysical methods can be most useful since they are non-destructive and rapid. The archaeologist can hope to chose digging priorities based on survey findings. Some sites (monuments or parks) contain sites or buildings that can not be disturbed at all, so geophysical sensing may provide the only means of studying the site. A combination of geophysical methods can be helpful as each method has its strengths and limitations. Archaeology is a time-honored exacting scientific discipline which provides us with some of our best information on human history and the past. It is to be hoped that more opportunities and sources of funding will develop so that modern geophysical methods can assist the archaeologist even more frequently than has been possible in recent years (please see more references in documentation).

D) Fluoride Dating      

What is Fluoride Dating?

Fluoride (or fluorine) dating is a relative dating method that can be used to date archaeological bone. As a relative dating method, it can determine the relative age of specimens, but cannot provide a calendrical date unless the fluoride chronology is calibrated with an absolute dating method. Bones are primarily composed of the mineral calcium hydroxy apatite. When exposed to water that contains fluoride, a fluoride ion (F) can replace a hydroxyl ion (OH-) in the bone mineral. The resulting fluor-apatite is more stable than the original form, thus the fluoride content of a bone will increase over time if it is exposed to a solution containing fluoride ions. Fluoride ions are present in trace amounts in most soils and ground waters. Over time, buried bones pick up fluoride ions from soil moisture or exposure to groundwater. Older specimens have higher fluoride contents than younger ones when burial conditions are identical. The requirement of identical burial conditions means that fluoride dating works best when it is applied within a single site with little variation in soil chemistry.

How is Bone Fluoride content measured?

Many different techniques can be used to measure bone fluoride content, but measurement by ion selective electrode is the easiest and simplest method available today. The fluoride selective electrode uses the same principle as the familiar pH electrode. When the electrode is placed in a solution that contains fluoride, it produces a

voltage that is proportional to the amount of fluoride in the solution. A calibration curve can be produced by measuring standard solutions of known fluoride concentration. The calibration curve is then used to determine the fluoride content of unknowns. A description of the method is given in: Schurr, Mark R.1989. Fluoride dating of prehistoric bones by ion selective electrode. Journal of Archaeological Science 16: 265-270.

What does Fluoride Dating offer?

It can be used to determine the relative dates of faunal materials. The relative dates can be used to date contexts that did not contain diagnostic artifacts or that did not provide carbon suitable for radiocarbon dating.

ˇ        It can be used to evaluate the integrity of an archaeological context. Relative dates can be used to identify the degree of mixing in contexts that were not obviously mixed or stratified.

ˇ        It can be used to study changing patterns of faunal utilization over time within a single site.

ˇ        It is economical, costing less than $20 per sample (with three replicate measurements).

ˇ        Fluoride dating uses very small samples. This example used 5mg samples, but one can successfully analyze samples as small as 0.5 mg. Compare this with a conventional radiocarbon date, which requires about 10 grams of bone and costs around $400.

ˇ        Fluoride dating can measure very small chronological differences. Samples with fluoride contents that differ by as little as 0.024 % can be statistically distinguished from each other. Under favorable conditions, this can represent a time resolution of 10 to 20 years!

Will Fluoride Dating work at any site?  

Fluoride dating has been successfully used in a wide variety of settings, ranging from extremely arid Sudanese Nubia, to the humid eastern USA. It has been applied to sites ranging from very old to very recent (for example, the famous Piltdown specimens contained both), and with bones that range from partially fossilized to less than a thousand years old. Fluoride dating of control samples and burial treatment clusters was used to establish the contemporaneity of the burial treatments at the Middle Mississippian Angel site in southwestern Indiana. Each of the clusters represents a different type of burial treatment.

What type of samples are required?

Fluoride dating works best when bones of similar density are compared. Therefore, it is rarely possible to mix results from skeletal elements with widely differing densities (i.e., femur cortical bone versus vertebral fragments), or to compare juveniles with adults, or to compare bones from very large or very small mammals. For faunal specimens long bone fragments are recommended, which are usually very abundant. For humans, either ribs or cortical bone fragments both give good results, as long as one type of bone is consistently used (for more reference please see Documentation)..

E) Chemical Analysis: Ceramic Petrology

What is Chemical Petrology?

Chemical analysis of pottery is the study of either presence/absence or, more usually, quantitative data on the chemical content of a ceramic body. It is almost always used in a comparative study, normally to establish an artifact's source, but can also be used to study the technology of ceramic bodies and glazes and the use of ceramics in metallurgy or glass working.

Why should I want it?

Chemical analysis can be carried out using very small samples. Indeed, results can be obtained non-destructively using X-Ray Fluorescence (XRF). It is thus a less destructive technique than thin-sectioning, the principal method of study used in Ceramic Petrology.

Despite the ability to get results from extremely small samples, there are disadvantages, of which the most obvious is that chemical analysis of a heterogeneous body will give wildly varying results, depending on which particular rocks or minerals are present in the sample. This, and other potential sources of error (or, to be more accurate, variation) are discussed below.

Technique:       

X-Ray Fluorescence (XRF)      

XRF is a bulk characterization technique for the rapid, simultaneous, and non-destructive detection of all elements heavier than fluorine. The sample is irradiated with x-rays and re-emits x-rays characteristic of its composition. The measurement process itself is non-destructive and thus in theory could be used on a complete or displayable artifact.

The X-Ray beam can either be focussed to analyze a small area, in the order of 100 microns across, or defocused to analyze a wider field. However, even in this mode the sampled area will be minute in comparison with that of other methods. This can be an advantage, in that a specific inclusion or feature can be studied, but for characterization it is a disadvantage.

     XRF is useful for identifying the colourants used on painted pottery and glazes. However, unless the machinery has been adapted it is not possible to analyze complete vessels or large fragments. When measured in air the results are at best semi-quantitative but greater accuracy is obtained when measuring in a vacuum. However, producing the vacuum slows down the measuring process.

     One way around the problem of variability and small sample area is to crush a sample of pot and produce a homogeneous pellet either by compression or fusing. However, the method is then no longer non-destructive, or quick, thus negating the major strengths of the method. One unique feature of XRF is the ability to measure silica and there is therefore a case for using this method for analyzing refractory clays.

Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES)

Both ICP-AES and ICP-MS work by vaporizing a sample of pottery dissolved in acid. This produces a stream of excited atoms which can either be measured through their mass (ICP-MS) or the wavelength of light (ICP-AES). Mass spectroscopy is much more powerful than Atomic Emission spectroscopy, but the measurement process is also up to four times as expensive.

Inductively Coupled Plasma Mass Spectroscopy

ICP-MS is an extremely accurate method of measuring element concentrations in the parts-per-thousand and parts-per-million range and can not only measure elements but separate isotopes. A large number of elements are measured by default and to a greater precision than with ICP-AES. In comparison with ICP-AES the increased accuracy has to be balanced against the fact that the major elements, measured in percent, cannot be measured. For ceramics, this could be a big disadvantage depending on the objectives of the analysis.

N eutron Activation Analysis

Nutron Activation Analysis uses powdered samples of pottery, as with ICPS. These samples are irradiated in an atomic reactor and the radioactivity of the samples is measured in two stages, to measure both short-lived and longer-lived radioactive isotopes (for reference please see documentation).

Implementation

LESSON  #1: Vocabulary words of Archaeology.

Objective: To increase student’s vocabulary.

Grade Level:   8 to 12 grades.

Time: As long as course last.

Procedure:

Since archaeology is very unfamiliar subjects for many students, it is my intention to teach them vocabulary of this subject.  One can even create a puzzle or word search from these vocabulary.   Students will write the definition of the words and discuss about them.

Activity

Vocabulary words    

Archaeology, Paleontology, Artifact, Site, Archaeologist, Excavation, Survey, Horizontal Distribution, Vertical Distribution, Grid, Unit, Stratigraphy, Strata, Stratum, Profile, Chronology, Context,Radiocarbon Dating, Specialists/Analysis, Prehistoric, Paleoindian Period, Nomadic and Archaic Period (more words will be added as kids will learn more).

More handouts on vocabulary and definitions

Analysis	The study and interpretation of artifacts, usually by scientists or specialists.
Archaeologist	A person who studies ancient people through the artifacts they leave behind.
Archaeology	The study of people through what they leave behind.
Archaic Period	The time after the Ice Age when people lived in North America. (8000-1000 B.C.)
Artifact	Object made, or used, or modified by people.
Chronology	The study of time.
Context	Looking at something in relation to the things around it.
Excavation	An archaeological dig, or the way archaeologists study sites.
Grid	The checkerboard-like system that archaeologists use to divide their sites into smaller digging units.
Horizontal Distribution	The way artifacts are distributed across a site.
Nomadic	A wandering existence in search of food.
Paleoindians	The earliest inhabitants of North America during the Ice Age. (11,000-8000 B.C.)
Paleontology	A branch of geology which studies plant and animal fossil remains.
Prehistoric	The time when people lived before the invention of writing.
Profile	A wall of a unit after it has been excavated, that shows the stratigraphy of a site.
Radiocarbon Dating	A method of dating organic remains (plant, animal, human).
Site	A place that contains artifacts and other remains left behind by people who once lived there.
Specialist	Someone, usually a scientist, who studies a particular area of research.
Strata	(Plural) Many layers.
Stratigraphy	The layers of soil and artifacts found within a site.
Stratum	(Singular) One layer.
Survey	A systematic method of walking and looking at the ground surface in search of sites.
Unit	A small 1x1-meter square in which archaeologists dig a site.
Vertical Distribution	The way artifacts are distributed downward within a site.
Woodland	The time when people settled in villages and planted crops for food. (1000 B.C. - A.D. 1350)

Assessments: Student’s understanding of words.

LESSON  #2: Archaeology Preservation Lab

Objective: This lab will give the children an opportunity to become an archaeologist. They will be imagining themselves excavating their own classroom at a time 5000 years into the future. There are four questions they will be answering in this lab.

1. What types of materials will preserve to be found 5000 years later?

2. What are the purposes of the objects found, assuming that we have never seen these objects before?

3. What does it mean to have found these objects together in one room?

4. What do these objects, collectively, tell us about the people living here 5000 years ago?

Grade Level:   8 to 12 grades.

Time: Approximately two days (or 4 hours).

Materials: All of the materials for this lab will be found in the classroom.

Procedure:

This lab consists of six parts, as follows:

Part 1:What is an archaeologist?
Ask the children what they think an archaeologist is.

(An archaeologist is a person who makes interpretations about the past based on information gathered through techniques of excavation in a systematic manner. This information in interpreted based on the association of the various objects with each other and the entire site. This association involves the relationships based on position, both vertically and horizontally, material, and design.)

Part 2:What types of materials will preserve?

Write a two column chart on the chalkboard. Label one column, "Materials Preserved," and the other, "Materials Not Preserved." Ask the children to give examples of the kinds of materials that will fill this chart.

(Materials Preserved: stone, metal, bone, fired clay, burnt wood. Materials Not Preserved: wood, plants, feathers, cloth, animal skins, paper.)

Part 3: Excavation

Have the children get into pairs. Ask each pair to get an object from the classroom they think will be found in 5000 years and bring it back to their desks.

Part 4: Interpretation

Tell them they are now archaeologists 5000 years in the future, and have just uncovered the object before them from this site. Remind them that they have never seen this object before, and have them fill out the first row on the Data Sheet. When they are done, have them rotate clockwise to the object found by another group and fill out the next row on the Data Sheet. Repeat this until all of the groups have recorded and interpreted each object. Discuss what they found out about each object.

Part 5: Interpretation on a larger scale

Ask the children to look at their data and try and find out what all of the objects seem to have in common, besides their material composition. Write their answers on the chalkboard. Ask them what it means to have found all of these objects together in one room. What was the use of the room 5000 years ago? Again, write their answers on the chalkboard. (How different were the responses of the different groups? Why was this? A good portion of their interpretation will be based on imagination. In this part of the lab we are trying to tie everything together so it may seem necessary to take the interpretations of different groups on different objects. In this sense the entire class is acting as one team. Try explaining this to the class and repeating Part 5 if there are problems with finding a uniform role of the room.)

Part 6: The Big Picture

Ask the children to think about what all of these objects and their interpretations might say about the people who lived here 5000 years ago. Discuss their ideas and write them on the chalkboard. Ask the children what they think is missing. What does this missing evidence do to our interpretations?   (Archaeology is based on fragmentary evidence. Whole industries and collections will vanish over 5000 years. Because of this missing evidence, many things about the past are only speculative, even to an archaeologist.)

Conclusion: What have we learned? We have learned that not everything around us will survive to tell our tale. Archaeologists are people who infer various information about past cultures from the fragmentary evidence they find. The associations of this evidence is the cornerstone of archaeological research. Only through a gathering and discussion of the ideas of various people can any real understanding about the past be achieved.

LESSON #3: Artifact.

Grade levels: 9 to 12 grades

Time: 45 minutes.

Objectives: Teach about Artifact.

Procedure:

Investigative Question:

How do life form, natural and man-made items compare'?
Skills: The students will compare different items found in the ground inside and around the science lab. They will be able to complete the following:

1. Name the items when seen.

2.      State whether the items are life form, natural or man-made.

3.      Explain how the items are the same or different from one another.

4. Group the items found.

Activity:

1.      Memory match

2.      Name the picture

3.       Group me with the friends

 
Procedure:

The students will be given 24 picture cards. Each card will represent either some type of life form, natural materials or man-made items found in the ground of the science lab. There will be a total of 12 different items and each item will have two (2) cards representing it (totaling 24 cards). All of the cards will be faced down, placed in six (6) rows across and four (4) rows down The students will be given ten (10) seconds to review the picture cards faced up. Bach student will take turns selecting two (2) cards . The pictures must be the same in order for them to be a match. The cards must be turned up one at a time. As each card is turned face up the student must state what item is on the card . After naming the item the student must state whether it's a life form, a natural or man- made item. If the student accomplishes the above task (matching the cards, name the item, then categorize the item ) they will win that set. If the student turns up two (2) cards that do not match they must stop and let the next student try. The students only continue when they get a match one set. The student with the highest amount of sets at the end of the game is the winner.

Materials:

Twenty-four (24) picture cards containing twelve (12) different items with two (2) cards of each item.

Life forms - ants, centipedes, earth worms, fossils

Natural items - dirt, pebbles, rocks, roots

Man-made - glass, plastic, metal, wood

LESSON #4: Archaeology and math.

Grade level: 9 to 12.

Time: This activity may be worked on throughout the year, or completed over several days as a review unit.

Objective: Students will practice math skills in a classroom simulation of an archaeological excavation.

Skills: Students will:

1.      Make accurate measurements using the metric system

2.      Find area and perimeter using formulas.

3.      Make accurate scale drawings.

4.      Sort and classify objects.

5.      Record and graph data.

Procedure:

Discuss archaeology with students-what it is, excavation and laboratory methods used, preservation of sites.  Show pictures of a trip to an archaeological site and if possible, visit a site with the students. Preparation:

1.      Set boundaries for a pretended archaeological site, including several units, in an outdoor area.

2.      Draw a mural of one or more walls of a unit.  Include strata changes and one more features in the profile.

3.      Have measuring tapes, graph paper and pencils available.

4.      Have students find perimeter and area of the field, or site, and the units.  Discuss orderly arrangement of units and have students determine how many units would fit in the site.  Have students make a scale drawing of the site.

5.      Inside, discuss how archaeologists excavate units in layers and screen soil to find artifacts.

6.      Give each group of students a bag of artifacts to classify and identify.  If desired add loose soil to the bags and let students screen out artifacts.  If possible, include artfacts related to the culture or time period being studied in history class.   When all artifacts for a unit are classified, have students make one or more graphs of the results:

                 a) Pictograph-number of each kind of artifact 

                 b) Line graph-number of each kind of artifact.

                 c) Bar graph-number of each kind of artifact.

                 d) Circle graph-percentage of each kind of artifact.

Students may choose one or more artifacts of which to make scale drawings.

7. Have students make a scale drawing of the profile on the mural using the same methods used at an archaeological site. Have students make separate drawings of feature plans.

LESSON # 5: Zoo pellet study (Biology)

Grade Level: 8 to 12

Time: Two Days.

Objective: -Students will be able to identify owl's meal by dissecting a pellet. Also, they will understand why buried bones are often incomplete and scattered when they're underground.

Method: Experiment, report - small groups, pairs, individuals (depending on level of students and availability of pellets)

Skills: Hands-on scientific details, writing observations, drawing conclusions, cooperative learning.

Materials:

1.      Owl pellets (already identified by zoo authorities to teacher)

2.      Trays (with an edge)

3.      Surgical gloves

4.      Tweezers

5.      Paper towels

6.      Water in a dish

7.      Paper and pencil (or special sheet prepared by teacher to be completed by students)

8.      Reference book (science encyclopedia)

Procedure:

Day 1 -- Soak pellet so it begins to pull apart. Gently pull "ball" apart with tweezers. Separate hair/feathers from bones. Using reference source, try to figure out what animal owl ate (bone size, skeleton features, hair/feathers)

Day 2 -- Write out the observation sheet and conclusions drawn.

Extensions:

Research digestive systems of owls, other birds, animals.

Special Notes: Project needs early preparation. Owls only produce one pellet per week, so zoos or other animal sanctuaries need to be contacted ahead of time to be able to collect enough specimens.

LESSON  # 6: Determining age of rocks and fossils.

Grade Level: 8 to 12

Time: two to four weeks.

Back Ground Information  

THE AGE of fossils intrigues almost everyone. Students not only want to know how old a fossil is, but they want to know how that age was determined. Some very straightforward principles are used to determine the age of fossils. Students should be able to understand the principles and have that as a background so that age determinations by paleontologists and geologists don't seem like black magic.

     There are two types of age determinations. Geologists in the late 18th and early 19th century studied rock layers and the fossils in them to determine relative age. William Smith was one of the most important scientists from this time who helped to develop knowledge of the succession of different fossils by studying their distribution through the sequence of sedimentary rocks in southern England. It wasn't until well into the 20th century that enough information had accumulated about the rate of radioactive decay that the age of rocks and fossils in number of years could be determined through radiometric age dating.

     This activity on determining age of rocks and fossils is intended for 8th or 9th grade students. It is estimated to require four hours of class time, including approximately one hour total of occasional instruction and explanation from the teacher and two hours of group (team) and individual activities by the students, plus one hour of discussion among students within the working groups.

Objective:

This activity will help students to have a better understanding of the basic principles used to determine the age of rocks and fossils. This activity consists of several parts. Objectives of this activity are:

1) To have students determine relative age of a geologically complex area.

2) To familiarize students with the concept of half-life in radioactive decay.

3) To have students see that individual runs of statistical processes are less predictable than the average of many runs (or that runs with relatively small numbers involved are less dependable than runs with many numbers).

4) To demonstrate how the rate of radioactive decay and the buildup of the resulting decay product is used in radiometric dating of rocks.

5) To use radiometric dating and the principles of determining relative age to show how ages of rocks and fossils can be narrowed even if they cannot be dated radiometrically.

Materials for each group

Block diagram (Table-1). Teacher can provide a diagram of a soil, which will contain different kinds of rock formation.   Students will create a table.

Table 1

Name of the rocks from oldest to most recently formed Radio active age                                              Limestone                           Sandstone   Slate   Pegmatite   Granite

2) Large cup or other container in which M & M's can be shaken.

3) 100 M & M's

4) Graph paper (Table-2)

 

Table-2

Run	Class Total	Team1	Team 2	Team 3	Team 4	Class Average
1
2
3

5) Watch or clock that keeps time to seconds. (A single watch or clock for the entire class will do.)

6) Piece of paper marked TIME and indicating either 2, 4, 6, 8, or 10 minutes.

7) 128 small cards or buttons that may be cut from cardboard or construction paper, preferably with a different color on opposite sides, each marked with "U-235" all on one colored side and "Pb-207" on the opposite side that has some contrasting color.

Part 1: Determining Relative age of rocks

Each team of 3 to 5 students should discuss together how to determine the relative age of each of the rock units in the block diagram (Table 1). After students have decided how to establish the relative age of each rock unit, they should list them under the block, from most recent at the top of the list to oldest at the bottom. The teacher should tell the students that there are two basic principles used by geologists to determine the sequence of ages of rocks. They are:

Principle of superposition: Younger sedimentary rocks are deposited on top of older sedimentary rocks.

Principle of cross-cutting relations: Any geologic feature is younger than anything else that it cuts across.

Part 2:  Radiometric Age-Dating

Some elements have forms (called isotopes) with unstable atomic nuclei that have a tendency to change, or decay. For example, U-235 is an unstable isotope of uranium that has 92 protons and 153 neutrons in the nucleus of each atom. Through a series of changes within the nucleus, it emits several particles, ending up with 82 protons and 125 neutrons. This is a stable condition, and there are no more changes in the atomic nucleus. A nucleus with that number of protons is called lead (chemical symbol Pb). The protons (82) and neutrons (125) total 207. This particular form (isotope) of lead is called Pb-207. U-235 is the parent isotope of Pb-207, which is the daughter isotope.

     Many rocks contain small amounts of unstable isotopes and the daughter isotopes into which they decay. Where the amounts of parent and daughter isotopes can be accurately measured, the ratio can be used to determine how old the rock is, as shown in the following activities.

Part  2a: Activity:

At any moment there is a small chance that each of the nuclei of U-235 will suddenly decay. That chance of decay is very small, but it is always present and it never changes. In other words, the nuclei do not "wear out" or get "tired". If the nucleus has not yet decayed, there is always that same, slight chance that it will change in the near future. Atomic nuclei are held together by an attraction between the large nuclear particles (protons and neutrons) that is known as the "strong nuclear force", which must exceed the electrostatic repulsion between the protons within the nucleus. In general, with the exception of the single proton that constitutes the nucleus of the most abundant isotope of hydrogen, the number of neutrons must at least equal the number of protons in an atomic nucleus, because electrostatic repulsion prohibits denser packing of protons. But if there are too many neutrons, the nucleus is potentially unstable and decay may be triggered. This happens at any time when addition of the fleeting "weak nuclear force" to the ever-present electrostatic repulsion exceeds the binding energy required to hold the nucleus together.

         Very careful measurements in laboratories, made on VERY LARGE numbers of U-235 atoms, have shown that each of the atoms has a 50:50 chance of decaying during about 704,000,000 years. In other words, during 704 million years, half the U-235 atoms that existed at the beginning of that time will decay to Pb-207. This is known as the half life of U- 235. Many elements have some isotopes that are unstable, essentially because they have too many neutrons to be balanced by the number of protons in the nucleus. Each of these unstable isotopes has its own characteristic half life. Some half lives are several billion years long, and others are as short as a ten-thousandth of a second.

        
            A tasty way for students to understand about half life is to give each team 100 pieces of "regular" M & M candy. On a piece of notebook paper, each piece should be placed with the printed M facing down. This represents the parent isotope. The candy should be poured into a container large enough for them to bounce around freely, it should be shaken thoroughly, then poured back onto the paper so that it is spread out instead of making a pile. This first time of shaking represents one half life, and all those pieces of candy that have the printed M facing up represent a change to the daughter isotope. The team should pick up and set aside ONLY those pieces of candy that have the M facing up. Then, count the number of pieces of candy left with the M facing down. These are the parent isotope that did not change during the first half life.

        
            The teacher should have each team report how many pieces of parent isotope remain, and the first row of the decay table (Table 2) should be filled in and the average number calculated. The same procedure of shaking, counting the "survivors", and filling in the next row on the decay table should be done seven or eight more times. Each time represents a half life. After the results of the final "half life" of the M& M are collected, the candies are no longer needed.

        
            Each team should plot on a graph (Number of unselected stones vs. runs :Half Life) the number of pieces of candy remaining after each of their "shakes" and connect each successive point on the graph with a light line. On the same graph each team should plot the AVERAGE VALUES for the class as a whole and connect that by a heavier line. AND, on the same graph, each group should plot points where, after each "shake" the starting number is divided by exactly two and connect these points by a differently colored line. (This line begins at 100; the next point is 100/ 2, or 50; the next point is 50/2, or 25; and so on.)

 After the graphs are plotted, the teacher should guide the class into thinking about:

1) Why didn't each group get the same results?

2) Which follows the mathematically calculated line better? Is it the single group's results, or is it the line based on the class average? Why?

3) Did students have an easier time guessing (predicting) the results when there were a lot of pieces of candy in the cup, or when there were very few? Why?

         U-235 is found in most igneous rocks. Unless the rock is heated to a very high temperature, both the U-235 and its daughter Pb-207 remain in the rock. A geologist can compare the proportion of U-235 atoms to Pb-207 produced from it and determine the age of the rock. The next part of this exercise shows how this is done.

Part 2b:  Activity:

Each team receives 128 flat pieces, with U-235 written on one side and Pb-207 written on the other side. Each team is given a piece of paper marked TIME, on which is written either 2, 4, 6, 8, or 10 minutes.

    
         The team should place each marked piece so that "U-235" is showing. This represents Uranium-235, which emits a series of particles from the nucleus as it decays to Lead-207 (Pb- 207). When each team is ready with the 128 pieces all showing "U-235", a timed two-minute interval should start. During that time each team turns over half of the U-235 pieces so that they now show Pb-207. This represents one "half-life" of U-235, which is the time for half the nuclei to change from the parent U-235 to the daughter Pb-207.

     
         A new two-minute interval begins. During this time the team should turn over HALF OF THE U-235 THAT WAS LEFT AFTER THE FIRST INTERVAL OF TIME. Continue through a total of 4 to 5 timed intervals. However, each team should STOP turning over pieces at the time marked on their TIME papers. That is, each team should stop according to their TIME paper at the end of the first timed interval (2 minutes), or at the end of the second timed interval (4 minutes), and so on. After all the timed intervals have occurred, teams should exchange places with one another as instructed by the teacher. The task now for each team is to determine how many timed intervals (that is, how many half-lives) the set of pieces they are looking at has experienced.

    
            The half life of U-235 is 704 million years. Both the team that turned over a set of pieces and the second team that examined the set should determine how many million years are represented by the proportion of U-235 and Pb-207 present, compare notes, and haggle about any differences that they got. (Right, each team must determine the number of millions of years represented by the set that they themselves turned over, PLUS the number of millions of years represented by the set that another team turned over.)

Part 3: Putting  Dates on Rocks and Fossils

For the block diagram (Table 1) at the beginning of this exercise, the ratio of U-235:Pb-207 atoms in the pegmatite is 1:1, and their ratio in the granite is 3:1. Using the same reasoning about proportions as in Part 2b above, students can determine how old the pegmatite and the granite are. They should write the ages of the pegmatite and granite beside the names of the rocks in the list below the block diagram (Table 1).

         Students will plot the half life on a type of scale known as a logarithmic scale, the curved line like that for the M & MTM activity can be straightened out (Percent of original U-135 vs. Million of Tears). This makes the curve more useful, because it is easier to plot it more accurately. That is especially helpful for ratios of parent isotope to daughter isotope that represent less than one half life. For the block diagram (Table 1), if a geochemical laboratory determines that the volcanic ash that is in the siltstone has a ratio of U-235:Pb-207 of 47:3 (94% of the original U-235 remains), this means that the ash is 70 million years old. If the ratio in the basalt is 7:3 (70% of the original U-235 remains), then the basalt is 350 million years old. Students should write the age of the volcanic ash beside the shale, siltstone and basalt on the list below the block diagram.

Questions for Discussion

1) Based on the available radiometric ages, can you determine the possible age of the rock unit that has acritarchs and bacteria? What is it? Why can't you say exactly what the age of the rock is?

2) Can you determine the possible age of the rock unit that has trilobites? What is it? Why can't you say exactly what the age of the rock is?

3) What is the age of the rock that contains the Triceratops fossils? Why can you be more precise about the age of this rock than you could about the ages of the rock that has the trilobites and the rock that contains acritarchs and bacteria?

    
        Note for teachers: Based on cross-cutting relationships, it was established that the pegmatite is younger than the slate and that the slate is younger than the granite. Therefore, the slate that contains the acritarch and bacteria is between 704 million years and 1408 million years old, because the pegmatite is 704 million years old and the granite is 1408 million years old. The slate itself cannot be radiometrically dated, so can only be bracketed between the ages of the granite and the pegmatite.

    
        The trilobite-bearing limestone overlies the quartz sandstone, which cross-cuts the pegmatite, and the basalt cuts through the limestone. Therefore the trilobites and the rock that contains them must be younger than 704 million years (the age of the pegmatite) and older than 350 million years (the age of the basalt). The limestone itself cannot be radiometrically dated, so can only be bracketed between the ages of the granite and the pegmatite.

    
        The Triceratops dinosaur fossils are approximately 70 million years old, because they are found in shale and siltstone that contain volcanic ash radiometrically dated at 70 million years. Any Triceratops found below the volcanic ash may be a little older than 70 million years, and any found above may be a little younger than 70 million years. The age of the Triceratops can be determined more closely than that of the acritarchs and bacteria and that of the trilobites because the rock unit that contains the Triceratops can itself be radiometrically dated, whereas that of the other fossils could not.

 

Documentation

 
References for History and Modern Archaeology

G. Daniel, A Hundred and Fifty Years of Archaeology (2d ed. 1975)

B. G. Trigger, A History of Archaeological Thought (1989)

R. J. Wenke, Patterns in Prehistory (3d ed. 1990)

G. R. Willey and J. Sabloff, A History of American Archaeology (1990)

I. Hodder, Reading the Past (2d ed. 1991).

Archaeological Sites of the Southwest.

* Aztec Ruins National Monument :{Anasazi} (Aztec, NM), Principal Ruins: Aztec ruin (400-room, 9-kiva pueblo); restored/ recreated great kiva; several other sites not open to public Access: $3/person entrance fee. Open 8am-6pm June-August; 8am-5pm rest of the year. Information: Visitor's Center; Contact Superintendent, Aztec Ruins National Monument, P.O.Box 640, Aztec, NM 87410. Phone 505- 334-6174.

* Bandelier National Monument:{Anasazi) (near Los Alamos, NM), Principal Ruins: Tyuonyi (large pueblo), Long House (cliff dwelling), Ceremonial Cave (and recreated kiva); Stone Lions (still a Indian religious site); Painted Cave. Access: $5/vehicle. Many ruins available via a short hike through Frijoles Canyon. Information: Visitor's Center open 8am-6pm June - August, 8am-4:30pm rest of year. Phone 505-672-3861.

Casamero Ruins {Anasazi} (near Prewitt, NM) [* NPE] Principal Ruins: small pueblo (occupied 1000-1125 AD) and unexcavated great kiva. Access: take Exit 63 off I-40 at Prewitt, then east of exit junction of US Hwy 66, McKinley County Road 19 leads north to the Plains Escalante Generating Station. Follow that road 4 miles. Information:

 *  Chaco Culture National Historical Park: {Anasazi) ,Principal Ruins: Pueblo Bonito, Great Kiva of Casa Rinconada; Chetro Ketl, Una Vida, Hungo Pavi, Kin Kletso, Casa Chaquita, Pueblo del Arroyo; also Sun Dagger Solar/Lunar Observatory (on Fajada Butte - not accessible); over 3.500 recorded sites (most not accessible) Access: $8/vehicle entrance fee. Access to the Park is via long dirt roads: From the north, Chaco can be reached by turning off NM Hwy. 44 at Nageezi and following San Juan County Road 7800 for 11 miles to New Mexico Hwy 57; the Visitor's center is 15 miles ahead on Hwy 57. From the south, pick up New Mexico Hwy 57 via Grants or Crownpoint. Both of these routes include at least 20 miles of unpaved roads. Self-guiding trails explore seven of the Park's ruins including Pueblo Bonito, Chetro Ketl, Pueblo del Arroyo, Casa Rinconada, and 3 village sites. Four other trails for day hiking lead into the back country (permits required). Information: Visitor's Center open 8am - 6pm June-August; 8am-5pm rest of year. Contact: Superintendent, Chaco Culture National Historic Park, Star Route 4, Box 6500, Bloomfield, NM 87413. Phone 505-786-7014. 

* Coronado State Monument {ancient Pueblos} (near Bernalillo, NM), Principal Ruins: Kuaua Pueblo; reconstructed kiva with murals Access: $2 entrance fee. Located along US Hwy 44, 1 mi. w of Bernalillo. Information: Phone 505-867-3304.  

* Dittert Site {Anasazi} (about 45 mi. se of Grants, NM), Principal Ruins: small pueblo and kiva, mostly backfilled/covered over Access: drive 5 miles east of Grants on I-40, then continue 9 miles south on SR 117 to BLM ranger station (ask directions). Information:

* El Morro National Monument: {Anasazi} (40 mi. w of Grants, NM), Principal Ruins: Atsinna ruin - originally over 500 rooms, all that's been excavated is around 20 rooms and 2 kivas. Also Inscription Rock (petroglyphs and grafitti dating back over 500 years) Access: Entrance fee $4/vehicle or $2/person. Located on SR 53, 40 mi west of Grants and 30 miles east of Zuni, NM. Information: Contact Superintendent, El Morro National Monument, Rt. 2, P.O. Box 43, Ramah, NM 87321. Phone 505-783-4226.

* Gila Cliff Dwellings National Monument {Mogollon} (44 mi. n of Silver City, NM) , Principal Ruins: cliff dwellings (about 40 rooms built circa 1270 AD); pithouses dating back to around 300 AD. Access: located at the end of SR 15, 44 miles north of Silver City. Information: Phone 505-536-9461.

* Hawikuh Ruin: {Anasazi} (12 mi. s of Zuni Pueblo, NM), Principal Ruins: large in size, but these are mostly collapsed mounds of rubble. Access: obtain permission to visit the site from the Zuni Tribal Office (505-782-4481); for direction to the site, call the tribal archeology department at 505-782-4814.

* Jemez State Monument: {ancient Pueblos} (near Jemez Springs, NM), Principal Ruins: pueblo mounds plus 1621 AD church and monastery Access: Entrance fee $2. Located on SR 4 just north of Jemez Springs. Information: Phone 505-829-3530.

* Pecos National Historic Park {ancient Pueblos} (near Pecos, NM), Principal Ruins: North Pueblo and South Pueblo Access: $5/vehicle entrance fee. Park is 2 miles south of Pecos on New Mexico Road 63. self-guiding 1.25 mile hike; guided tours available on request. Information: Visitors Center open 8am-6pm June-Aug., 8-5 rest of year. Phone 505-757-6414/6032.

* Poshuouinga Ruins: {ancient Pueblos) (near Abiquiu, NM), Principal Ruins: large pueblo (over 700 ground-floor rooms surrounding 2 large plazas with a large kiva in larger plaza) Access: located on US Hwy 84 2.5 mi. south of Abiquiu. Information:

Petroglyph National Monument {ancient Pueblos} (Albuquerque, NM) [*] Principal Ruins: over 15,000 petroglyphs (most dating from 1300 AD to 1680 AD, but some dating back 3000 years) Access: No entrance fee. Several sections in northwestern Albuquerque. Information: Petroglyph National Monument, P.O. Box 1293, Albuquerque, NM 87103 (Phone 505-768-3316) or call City of Albuquerque Division of Open Space at 505-873-6620.

* Pueblitos of Dinetah : {ancient Pueblos} (NE of Farmington, NM), Principal Ruins: 8 small pueblos dating from 1715 to 1754. Access: get detailed directions from BLM; the ruins are only accessible via long drives on dirt roads. Information: Bureau of Land Management phone 505-761-4505 or 505- 327-5344.

* Puye' Cliff Dwellings: {ancient Pueblos) (Espanola, NM), Principal Ruins: combination of cliff dwellings and mesa top pueblos believed to originally have over 1,000 rooms. Access: $5 admission. 11 miles west of Espanola via New Mexico Roads 30 and 5 in the Santa Clara Indian Rservation. Mesa top accessible via gravel road or hiking. Open 9am-6pm. Guided tours available by reservation. Information: Phone 505-753-7326.

* Salinas Pueblo Mission National Monument:{ancient Pueblos} (Mountainair, NM) Principal Ruins: Gran Quivira, Quarai, Abo Access: No entrance fee. Information: Visitor Center at Broadway & Ripley Streets in Mountainair. Phone 505-847-2585.

* Salmon Ruin:{Anasazi} (Bloomfield, NM), Principal Ruins: Salmon ruin (11th century pueblo and Chacoan outlier) Access: $1 admission. 2.5 miles west of Bloomfield via U.S. Hwy 64. Information: 505-632-2013.

* Three Rivers Petroglyph Site:{Mogollon} (30 mi. n of Alamogordo, NM), Principal Ruins: some 20,000 petroglyphs dating from 900 AD to 1400 AD. Access: go 30 miles north of Alamagordo on US Hwy 54; turn east at the Three Rivers intersection and go 5 miles to the site. One trail leads through petroglyphs and another to the excavated ruins. Information: Phone 505-525-8228.

* Village of the Great Kivas: {Anasazi} (on Zuni Reservation, NM), Principal Ruins: small (18 room) pueblo with 2 unexcavated great kivas. Access: located 17 miles from Zuni Pueblo. To visit the site, contact the Zuni Tribal Office at 505-782-4481 for permission and 505-782-4814 for directions (from tribal archaeology dept.).

* Maxwell Museum of Anthropology: Albuquerque, NM, Located on the University of New Mexico campus.

* Museum of Indian Arts and Culture: Santa Fe, NM, P.O Box 2087, Santa Fe, NM 87504-2087 Phone: 505 827-6344

*Western New Mexico University Museum: Silver City, NM

References for Carbon Dating.

Archaeology by C.Renfrew, ISBN 0-500-27867-9,1998,Third edition, pages 131-149, London, Thames och Hudson http://medicine.wustl.edu/~ysp/MSN/hosts/archives/877696988.Es.r.html

 http://units.ox.ac.uk/departments/rlaha/leaf_are.html

Kemi för gymnasieskolan Y.Lindberg, ISBN 81-27-61033 , First edition, 1995, pages 183 -184, Stockholm, Natur/Kultur

Chemistry S, Zumdahl, ISBN 0-669-41794-7, 1997, Fourth edition, pages 996-1010, Boston, Mass:Houghton Mifflin

Arkeologi, Kristina Ambrosiani ISBN 91-86742-38-8 Gamleby: arkeo-förl. 1989

The Cambridge encyclopedia of archeology, Andrew Sherratt ISBN 0-521-22989-8 Cambridge, Cambridge U.P. 1980

http://kroeber.anthro.mankato.msus.edu/archaeology/dating/thermoluminescence.html

References for Geophysical Methods

Fundamentals of Geophysics, by William Lowrie

Geodynamics, by Donald L. Turcottel, et. Al.

Earth Surface Processes, by Philip A. Allen

Priciple of Geophysics, by N.H. Sleep, K. Fujita

References for Fluoride Dating.

Callaghan, R. T. 1986 Analysis of the fluoride content of human remains from the Gray site,                 Saskatchewan. Plains Anthropologist 31(114):317-328.

Ezzo, James A. 1992  A refinement of the adult burial chronology at Grasshopper Pueblo. Journal of                 Archaeological  Science 19:445-458.

Gregory, David and Mark R. Schurr  2000  Fluoride Dating within an Early Agricultural Period                Settlement in the Tucson Basin.  Poster presented at the Society for American Archaeology                65th Annual Meeting, Philadelphia, Pennsylvania.

Haddy, A. and A. Hanson. 1981  Relative dating of Moundville burials. Southeastern
            Archaeological Conference Bulletin 24: 97-99.  

Haddy, A. and A. Hanson  1982 Nitrogen and Fluorine Dating of Moundville Skeletal Samples              Archaeometry 24:37-44.

Johnsson, K.  1997 Chemical dating of bones based on diagenetic changes in bone apatite. Journal              of Archaoeological Science 24:431-437.

Middleton, J. 1844 On fluorine in bones, its source, and its application to the determination of the              geological age of fossil bones. Proceedings of the Geological Society (London) 4:431-433.

Oakley, K. P. and C. R. Hoskins  1950 New Evidence on the antiquity of Piltdown man. Nature              165:379-382.

Parker, R. B., J. W. Murphy, and H. Toots. 1974  Fluorine in fossilized bone and tooth: distribution              among skeletal tissues. Archaeometry 16: 98-102.

Schurr, Mark R. 1989 Fluoride dating of prehistoric bones by ion selective electrode. Journal of              Archaeological Science 16: 265-270.

Schurr, Mark R. 1989 The Relationship between Mortuary Treatment and Diet at the Angel Site.              Ph.D. dissertation, Indiana University.

1998 Fluoride dating of faunal materials: a neglected tool. Poster paper presented at the Society  for              American Archaeology, 63rd Annual Meeting, Seattle, Washington.

Schurr, Mark R. and David J. Hally  1999  Fluoride Dating Burials from Short-Occupation Sites: A              Mississippian Period Test of the Technique.  Poster presented at the Society for American              Archaeology 64th Annual Meeting, Chicago, Illinois.

Schurr, Mark R. and Sherri L. Hilgeman  1990 Fluoride Dating and Pottery Chronology at Angel.            Midwest Archaeological Conference, Evanston, Illinois.

Wiener, J. S., K. P. Oakley and W. E. Le Gros Clark  1950 The solution of the Piltdown problem.              Bulletin of the British Museum (Natural History). Geology 2(3):139-146.

Reference for Chemical Petrology

John S. Isaacson and Thomas F. Aleto (1989). Petrographic analysis of ceramic thin sections from              La Puna Island, Ecuador. Archeomaterials, 3, 61-67.

Alan Vince (1989). The petrography of Saxon and early Medieval pottery in the Thames Valley. In:              Julian Henderson (ed.) Scientific Analysis in Archeology. University of Oxford, Committee              for Archaeology, Monograph 19, pp. 163-177 (Chapter 7).

J. Donahue, D.R. Watters and S. Millspaugh (1990). Thin section petrography of northern Lesser              Antilles ceramics. Geoarcheology, 5(3), 229-254.

Christopher M. Gerrard (1991). Sedimentary petrology and the archaeologist: the study of ancient              ceramics. In: Morton, A.C., Todd, S.P. and Haughton, P.D.W. (eds.) Developments in             Sedimentary Provenance Studies, Geological Society Special Publications No. 57, 189-197.

Stacey C. Jordan, Carmel Schrire and Duncan Miller (1999). Petrography of locally produced              pottery from the Dutch Colonial Cape of Good Hope, South Africa. Journal of                     
   Archaeological Science, 26, 1327-1337.The following papers by Cordell and Hegmon              are good examples of what you can do with temper and provenance determination.

Ann S. Cordell (1993). Chronological variability in ceramic paste: A comparison of Deptford and             Savannah period pottery in the St. Mary's River region of northeast Florida and southeast             Georgia. Southeastern Archaeology, 12(1), 33-58.

Michelle Hegmon (1995). Pueblo I ceramic production in southwest Colorado: Analyses of igneous              rock temper. Kiva, 60 (3), 371-390.

The paper by Dickinson et al is a nice example of work in the Pacific and especially useful if you are working with either carbonates or volcanoclastic sediments and are trying to figure out how to correlate.

William R. Dickinson, Brian M. Butler, Darlene R. Moore and Marilyn Swift (2001) Geologic              source and geographic distribution of sand tempers in prehistoric potsherds from the Mariana              Islands. Geoarcheology, 16(8), 827-854.