IMAGING OHIO EARTHWORKS USING GEOPHYSICAL INSTRUMENTS

Ohio abounds in ancient earthwork sites—linear embankments and ditches of various sizes and shapes, including circles, squares, octagons, and a variety of others. While perhaps 100-150 of Ohio's 550-600 earthworks have been mapped in detail, most in the 1800s, the majority have not. A mere 15-20 of Ohio's earthworks are protected in parks; the rest are privately owned and thus left to an uncertain fate. Many have already been totally destroyed.

One of the biggest issues in studying Ohio's earthworks is the most fundamental—they can be quite hard to find on the ground or in aerial photographs since most have been flattened by 150+ years of agriculture. This is where geophysical survey plays a vital role in relocating earthworks. Over the past five years, I have surveyed all or part of dozens of earthwork sites all across southern and central Ohio. Gladly I can report that while most are exceptionally difficult to see at the surface with the unaided eye, Ohio's earthworks are readily imaged with geophysical instruments. Of course, at 1000+ feet across, some of these earthworks require a considerable amount of time to survey. But, as I show in this presentation, this is time well spent as nearly every earthwork surveyed to date has something new to offer in the geophysical data, from subtle changes in the shape and size of the earthworks to the presence of totally unknown enclosures.

Geophysical survey is a new frontier in Ohio earthwork research. Though its application is not new to the study of earthworks in Ohio, advancements in instrumentation now allow for the complete survey of even the largest earthwork complexes (i.e., 100+ acres). Like the Nineteenth Century surveyors who pioneered the mapping of Ohio's earthwork sites, today's geophysical surveys are radically changing our image of the ancient past.