The Black Tor (Avon) stone alignment is of the double type and is composed entirely of small stones. The alignment leads from a cairn and extensive views of the sea are available along its entire length. Despite its relatively short length it would appear that the sea views at the top and bottom of the row are different in character.
Viewshed (red) from the top of the Black Tor (Avon) stone alignment. According to Heywhatsthat an incredible ten separate views of the sea are available (Source: Heywhatsthat.com).
The viewshed from the lower end of the row includes eight separate sea views. The disappearance of two sea glimpses may have been significant to the builders of the row or perhaps they were just interested in the sheer quantity of separate views available from this hill. The original length of this row is not known and it is possible that it once extended to a point where the sea views disappeared entirely. If so, the gradual swallowing up of the sea, one element at a time would have been indicated by a series of significant points along its length (Source: Heywhatsthat.com).
Simplified map highlighting those areas (red) which are visible from the lower end of the row, but are not visible from the top (blue). Source: Heywhatsthat.com
The differences in the viewshed between the top and bottom of the row are limited, but despite this a cairn at Old Hill and cairns on Butterdon Hill appear as you walk south eastward down the row. The revealing of one or more broadly contemporary site along the length of a row is a common characteristic of the longer rows and strongly suggests that the row builders incorporated this “treat” into their design. The rows seem to have been carefully sited to maximise limit of visibility features and here at Black Tor (Avon) the long cairn at Corringdon Ball, stone alignment at Butterdon East and cairns at Three Barrows and Grippers Hill are all included. The visual relationships between the longer stone rows and their landscape is obvious and the the way in which they were laid out allows them to interact with maximum effect with other places of contemporary significance. Appreciation of this detail means our understanding of the rows whilst far from complete is less enigmatic.