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Earthen Mounds

Excavation Techniques

Objects are removed from a mound in a systematic process of mapping and retrieval known as excavation. To begin excavating a mound, an archaeologist may dig a trench around the periphery and proceed to dig in piewedged sections, exposing each successive layer of burial. The area is sketched and photographed, and the location of each individual object recorded. Skeletal remains are examined for position (for example, extended or flexed) and for the direction of the burial along the cardinal points (north, south, east, or west).

After removal from the mound, objects are assigned a date according to one of several procedures, the most common of which is carbon-14 dating. Carbon-14 (or radiocarbon) is a radioactive isotope that is present in the atmosphere and absorbed into the tissues and bones of all living things. After death, carbon-14 is no longer absorbed but begins to decay to nitrogen at a fixed rate, or half-life, of approximately 5,730 years. Because carbon-14 decays at this fixed rate, an estimate of the age of an object can be made based on the rate of decay of its radiocarbon.

New methods of excavation are being developed to avoid disturbing the underground contents of mounds. At the Cahokia site, researchers at the University of Southern Illinois at Edwardsville are using subsoil remote sensors. Linked to above-ground computers, the sensors relay electrical readings that determine the composition of the underground objects on the basis of their electrical properties.



Hamblin, W.K., and E.H. Christiansen. Earth's Dynamic Systems. 9th ed. Upper Saddle River: Prentice Hall, 2001.

Hancock P.L., and B.J. Skinner, eds. The Oxford Companion to the Earth. Oxford: Oxford University Press, 2000.

Jennings, Jesse D. Prehistory of North America. 3rd ed. Mountain View, CA: Mayfield, 1989.

Mound Builders and Cliff Dwellers. Alexandria, VA: Time-Life Books, 1992.

Myron, Robert. Mounds, Towns and Totems: Indians of North America. Cleveland and New York: World Publishing Company, 1966.

Christine Molinari


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—A radioactive isotope of carbon that decays at a uniform rate in living matter, used to determine the age of archaeological finds.

Charnel house

—A building where dead bodies or bones are kept.

Effigy mound

—A mound constructed to represent a living being or an abstract shape.


—The step-by-step removal of buried objects at an archaeological site.

Grave goods

—Personal possessions, such as weapons and tools, buried with the deceased for use in the afterlife.

Additional topics

Science EncyclopediaScience & Philosophy: Molecular distillation to My station and its duties:Earthen Mounds - The Hopewell Culture (c. 2300 B.c.c. A.d. 400) - Burial mounds