In a field to the south-west of a turlough, the seasonal lake unique to the karst limestone landscape of the west of Ireland, a set of earthworks at Ballynastaig in County Galway existed clearly enough in December 1982 to be recorded and described in some detail, then disappeared entirely from view a decade later beneath a crop.

When first inspected in 1982, the earthworks lay just south of a fulacht fia, a type of prehistoric cooking site typically identified by a mound of fire-cracked stones left over from repeated use of water-filled troughs for boiling meat. One of the earthworks was square in plan and defined by low, grassed-over walls, which is itself an unusual enough form to warrant attention; most earthwork enclosures of early Irish date tend toward the circular. By June 1992, the field had been brought into tillage and planted with oats, and no surface traces of the earthworks could be found. Whether they had been obscured by the crop and its cultivation, or disturbed more permanently, the record does not say.

What the site illustrates, quietly but effectively, is how provisional the archaeological landscape really is. Features that have survived centuries of weather and grazing can slip from view within a single growing season, leaving only the earlier record as evidence that they were ever there.