At Aderrig, a series of enclosures shows up as crop marks in satellite imagery, the kind of subtle discolouration in a growing crop that betrays buried boundaries underneath. Crop marks form when buried walls, ditches, or banks affect the soil's moisture and nutrients above them, causing the vegetation to grow differently, and in dry summers the effect can be striking enough to read almost like a map.

The enclosures were identified in a DigitalGlobe orthoimage captured between 2011 and 2013, and were noted by researcher Tom Condit in March 2015, with the findings compiled by Paul Walsh. They sit along the western and southern boundaries of a known ecclesiastical enclosure at Aderrig, recorded in the Sites and Monuments Record as DU017-028001. The prevailing interpretation is that these crop marks represent the remains of a field system that once served the early church site, the kind of carefully managed agricultural ground that would have supported a monastic or ecclesiastical community. Early Irish ecclesiastical sites frequently organised land around them into defined plots for cultivation, grazing, and other practical purposes, and the boundaries of such systems could persist in the soil for centuries after the structures above ground had disappeared entirely.

There is little to see at ground level, and that is rather the point. The site is one best approached through the aerial photographs now accessible via mapping platforms such as Google Maps, where the crop marks documented in 2015 may still be visible depending on the season and the state of the current crop. If you are in the area, the broader ecclesiastical site at Aderrig provides some above-ground context, and knowing that the faint geometry of old field boundaries lies just beneath the surface of the surrounding land gives the ordinary-looking fields a different quality altogether.