Two early aerial photographs, one from 1938 (Figure 17), and one from 1954 (Figure 18), show Cavanaugh Mound and the surrounding terrain before much of it was covered by urban development. The 1938 photograph may be the earliest image of Cavanaugh ever taken. The mound's location is clearly visible in both images as a patch of trees surrounded by cultivated fields. The cleared summit of the mound is also visible in the 1938 image, but the resolution of the photographs is too low for finer details to be expressed.
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 Figure 18. Aerial photograph taken in August of 1954. North is to the top. Arrow points to the Mound. USDA aerial photo AWA-1N-12. |
Naturally occurring prairie mounds are visible in both photographs, covering the entire landscape for several hundred meters around the mound. Prairie mounds occur throughout much of the western United States, generally occurring in large fields within river floodplains or terraces. In areas where they are not plowed, eroded, or otherwise disturbed by modern land use practices, they are generally one to two meters tall. The prairie mounds surrounding Cavanaugh are about 20 m in diameter and closely spaced, creating a regular pattern across much of the landscape. The soil stratigraphy of prairie mounds is ideally suited to studies of prehistoric landscape modification. Because the upper, organic-rich A horizon contours the surface of the mounds and is darker than the underlying soil, the truncation or leveling of a mound leaves behind a lighter-colored patch where the mound used to be. Such patches are easily identified in aerial photographs as distinct from un-truncated prairie mounds, indicating a landscape modification at least more recent than the time it takes for a well-developed A horizon to form.
Immediately west of the mound (see Figure 17) is an irregularly-shaped area of apparently truncated prairie mounds, not corresponding to any field edge or other historic land use pattern. These are not as well expressed in the 1954 aerial photograph, possibly due to moisture conditions or ground cover. These mounds may have been leveled long before the fields were plowed in historic times, possibly contemporaneous with the mound construction or use. The prairie mounds may have been used for mound fill, or the area may have been leveled flat for use as a plaza within an area of otherwise undulating topography.
The majority of the land in both photographs is in open field. Within 1 km of the mound, only about 13% (42 out of 314 hectares) is covered by trees or buildings that obscure the prairie mound pattern (determined through a simple GIS model derived from the aerial photographs). Besides the patch just west of Cavanaugh, there are no disruptions in the regular patterns made by prairie mounds that are not accounted for by modern land-use practices. Cavanaugh Mound therefore appears to be alone on the landscape, and not part of a group of mounds in close association.