Historic graves located in a modern city park
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Historic graves located in a modern city park

Archaeologists used several geophysical tools including GPR to search for 19th century graves in a Charleston, West Virginia city park that was once a cemetery.

By Jarrod Burks, Ph.D.
Ohio Valley Archaeology, Inc.


hio Valley Archaeology, Inc. in collaboration with West Virginia State University, conducted geophysical survey work in Ruffner Memorial Park on behalf of the City of Charleston, West Virginia. The work focused on locating graves once associated with the Ruffner Cemetery that is now a city park called Ruffner Memorial Park. The cemetery was founded in 1803 by the Ruffner family, who held an extensive tract of land along the Kanawha River above the fledgling city of Charleston (Figure 1).

As Charleston grew, a one-acre parcel including the Ruffner family cemetery was sold to the city for use as a city burial ground from 1831 to 1871, at which point the new Spring Hill Cemetery became the city’s burial ground. While as many as 50 burials were exhumed from the Ruffner Cemetery and moved over to the Spring Hill Cemetery, many were left in place.

In the 1920s, the land was converted from a cemetery to a park. The remaining stone markers were uprooted, laid flat on the ground, and the entire one-acre parcel was covered over with 2 feet of fill.

The goals of the geophysical surveys were to (1) detect possible graves, (2) locate buried marker stones, and (3) identify other components of the cemetery such as plot boundaries and internal paths or roads.

Figure 1
The location of Ruffner Memorial Park, formerly Ruffner Cemetery in the city of Charleston, West Virginia.

While the survey included data from GPR, magnetic gradiometry, and earth resistance, this story highlights the results from the GPR data.

Detecting Graves with Geophysical Instruments

Graves are notoriously difficult to detect with geophysical survey instruments and often for unpredictable reasons. In some cemeteries every single grave might be detected while in others the graves are totally invisible to the instruments.

Three main aspects of graves determine their detectability in geophysical surveys: the grave shaft and the soils within and around it, the presence of burial vaults, and the type of coffin used and whether it is still intact.

Host Soil: Most of this difference in detectability stems from variability in the types of soils found in the areas used for burial, such as sandy soils versus clayey soils. Some soil types facilitate grave detection more than others.

Figure 2
Idealized examples of graves and their components.

Grave Shaft: Perhaps the most important aspect of older graves (i.e., 19th century and earlier) for successful detection during geophysical surveys is the grave shaft and its fill. Grave shafts are oval to rectangular holes excavated two to six feet into the ground. Their horizontal extent varies widely and is dependent on the size of the grave’s occupant (e.g., adult versus child) and the use of a coffin and/or a burial vault. Larger grave shafts, such as those of adults, are more likely to be detected by geophysical instruments than those of smaller, adolescent burials.

The type of soil placed into the grave shaft is also important for detection with geophysical survey devices. The sediments in grave shafts are detectable because their properties are significantly different (i.e., they are disturbed) than the surrounding, intact soils. However, a grave shaft dug into soil without distinctive layers will be less detectable than one dug into soil with numerous, distinctive layers. In the extreme, a hole dug into a homogeneous medium, such as dune or beach sand, that is then backfilled with the same sand may be even more difficult to detect when looking for soil differences in GPR data.

Several other soil characteristics also factor into grave shaft detectability. Because the soil properties (porosity, compactness, etc.) of grave shaft fill differ from the undisturbed soil that surrounds them, grave shafts tend to hold and drain moisture differently than their surroundings. Thus, differential soil moisture plays a key role in grave detectability. For example, recent heavy rains can make the tops of grave shafts easier to detect with GPR.

Interruptions or disturbances of soil layers, which are common to all graves, can sometimes be detected by GPR. Many graves, especially older ones, experience subsidence when the coffin collapses and the grave shaft fill settles (Figure 2, grave 2). This leaves a depression at the surface. Often, the soil brought in to fill the subsided grave is obtained from a different source than the original grave shaft fill. This different soil is sometimes detectable with GPR.

Burial Vaults: Of course, what is in the grave is also a major contributor to detectability—reinforced concrete vaults are quite easy to detect with nearly every kind of survey instrument and in any soil type (Figure 2, grave 3).

Nearly all modern graves in the United States involve placing a coffin in a subsurface burial vault—this practice is also used in many other parts of the world. Older graves sometimes contain vaults made with brick or wood. Whatever the material, vaults will certainly impact the soil moisture levels present in the grave, making them more detectable with GPR, assuming it can penetrate deep enough into the ground.

Coffins: The type of coffin may also affect a grave’s detectability during a geophysical survey. Most wooden coffins will not be detected, and in older cemeteries many wooden coffins have collapsed and rotted away (Figure 2, grave 2). However, it is possible that intact wooden coffins, if they still contain an air pocket, will be detected by GPR (Figure 2, grave 1).

One type of coffin is much easier to detect with geophysical instruments – cast iron coffins/caskets. The first patent for a cast iron coffin in the U.S. was issued in 1848 and not long thereafter (1850s) iron coffins were used in cemeteries across the country, though in small numbers and largely for affluent individuals. GPR can detect metallic coffins of any type and may even be able to detect coffin hardware if it is large enough (nails are not likely large enough to detect with GPR), assuming the GPR signal can penetrate deep enough into the ground to reach the coffin, which is not always the case.

GPR is the most popular geophysical method that can penetrate deep enough into the ground, and with sufficient resolution for detecting human remains in graves. But even when the GPR can penetrate deep enough, bones and soil have similar GPR properties so there is usually not enough contrast to produce an interpretable reflection. Furthermore, the detection of very subtle features or objects, such as bones in soil, is complicated by the presence of other, more easily detected objects in most cemeteries. For example, tree roots can be very distinctive in GPR data, and they can obscure subtle GPR reflections next to and below them.

Other Subsurface Objects: In addition to graves, cemeteries also contain burial plot markers, walls, paths, roads, small building foundations, perimeter fences, wells, and other kinds of decorative/garden features. Finding the geophysical signatures of these kinds of features can be important to determining the structure of the cemetery, and by extension the general locations of graves, as well as the locations of the cemetery boundary. Cemetery edges can also be distinguished by activities that have occurred outside the cemetery. For instance, plowing around the edges of burial areas or cemeteries often creates distinctive plow patterns in geophysical data that are notably absent within the cemetery.

Soil Conditions at the Survey Site

The soil at Ruffner Memorial Park consists of darker fine sandy loam with a notable increase in clay that starts around 41 cm below surface and extends down to about 132 cm below surface, where a fine sandy loam picks up again. Sandy soils are ideal for GPR surveys as they allow the GPR signals to penetrate much deeper into the ground than silt or clay loam.

GPR Data Collection

A Noggin 500 system was used to collect the GPR data at Ruffner Memorial Park (Figure 3). A 500 MHz center frequency GPR is a mid-range frequency system that is suited to most archaeological applications. A 54-nanosecond time window was used to “listen” for return reflections from the transmitted GPR pulses to a depth of approximately 2 meters.

Figure 3
NOGGIN 500 MHz SmartCart system collecting data at the site.

At 500 MHz, GPR traces or “readings” are collected every 2 cm which translates to 50 traces per meter. GPR survey lines 20 meters long (1000 traces) were collected in grids with transects spaced at 25 cm intervals. A total of about 11,200 meters of data and 560,000 traces were collected for this survey.

GPR cross-sections showing the reflections interpreted as buried marker stones are shown in Figure 4.

Figure 4
GPR profiles showing examples of probable headstone-related anomalies (indicated by white arrows), which generally occur from 50-80 cm below surface.

The GPR amplitude depth slice from 65 to 85 cm is shown in Figure 5 with 15 possible headstones interpreted.

Figure 5
The GPR amplitude slice map from 65-85 cm below surface showing probable headstones—the yellow arrow indicates one of at least 15 probable headstones visible in this map.

Based on the GPR results, five locations thought to be marker stones were tested with a soil coring device and stone was encountered between about 55 cm and 80 cm (i.e., about 2 feet) below surface in all five cases.

GPR cross-sections showing the reflections interpreted as graves are shown in Figure 6.

Figure 6
GPR profile with white arrows indicating the distinct and subtle indications of graves—note how they occur deeper than 120 cm in the profile, below the many hyperbolas associated with tree roots, which are generally shallower than 80 cm below the surface.

The GPR amplitude depth slice from 120 to 140 cm is shown in Figure 7. High amplitude, localized reflectors are interpreted as graves.

Figure 7
The GPR amplitude slice map from 120 to 140 cm below surface showing probable graves—the yellow arrow indicates one of many graves visible in this map.


The geophysical survey results detected 207 probable graves and at least 41 buried marker stones, as well as a possible path original to the cemetery and two other large rectilinear features of uncertain origin (Figure 8). The detected stones and probable graves occur in distinct lines/rows, with a dense cluster near the middle of the park.

Figure 8
Interpretation of the geophysical survey results, showing probable and possible graves, as well as utilities and other features of possible interest.

The results of the geophysical survey work show that the cemetery was laid out in a regular grid pattern with rows running perpendicular to the road and the river. While probable graves and markers were detected across the park, the bulk of the detected graves are located near the center of the park, between the memorial monument and the road. Three iron burial containers were detected in both the GPR and magnetometer surveys (marked by stars in Figure 8). Two of these are associated with the original Ruffner plots at the western edge of the cemetery.

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