It looks, at first glance, like nothing more than a slight rise in the ground. But winter storms in recent years have torn into its northern side, and what they have exposed is a dense, tightly packed deposit of shells, mainly periwinkle with limpet mixed in, running across roughly five metres of exposed face and reaching up to 0.6 metres deep in places. A midden, in essence, is an ancient rubbish heap, the accumulated food waste of people who gathered shellfish from these shores repeatedly over long periods. The compressed layers here tell of sustained, habitual use of the coastline.

The midden was recorded by R. Long, and the shells begin just 0.2 to 0.3 metres beneath the sod and a layer of sand. Burnt stone and charcoal-stained soil were also noted among the deposit, and a fragment of what may be mudstone was found loose nearby. More telling still is the relationship between this site and a little-used coastal trackway that runs south-south-east from a late-medieval church standing about 450 metres to the north-north-west. The track partially overruns the western edge of the platform, meaning the midden pre-dates the trackway, and the shell material actually extends beneath the track's kerbing, visible intermittently along its edge. A comparable midden at Kerraunngark South, on a neighbouring part of the Connemara coast, has been dated to the Mesolithic, that is, the Middle Stone Age, a period in Ireland broadly spanning from around 8000 to 4000 BC. Given the close similarities in form and coastal location between the two sites, the deposit at Tír An Fhia may share something of the same antiquity.

The site sits along a shoreline that is not heavily visited, and the exposed shell layer is most clearly visible where storm erosion has cut into the northern face of the platform. The intermittent visibility of midden material beneath the old trackway kerbing gives a sense of how much may still lie undisturbed beneath the grass.