Field systems of this kind are among the more quietly remarkable survivals in the Irish archaeological record. They appear as low earthen banks, stony ridges, or subtle changes in vegetation, the remnants of organised agricultural land use that can date anywhere from the Bronze Age through to the medieval period, depending on the site. In the boggy terrain of Mayo in particular, such features are sometimes preserved almost by accident, sealed beneath layers of peat that protected them from the plough and from generations of later land improvement.