The local Historic Environment Record, SMR 7216, classifies the mound as an artificial mound and reads:
Located <50m from the coast edge. A very large grassy mound is located within the graveyard at Levenwick. It measures some 40m in diameter and stands up to 7m in height. There are sand dunes in the area, along with many small grassy mounds, which are probably of natural origin. It is probable that much of the make up of the mound comprises windblown sand, but the large size and artificial appearance of this feature strongly suggests the presence of substantial buried structures, possibly an ancient church (Fojut, The Ancient Monuments of Shetland, 1993, 111) which may itself have been built over an earlier settlement or broch site. A curvilinear depression to the W side of the mound may mark the location of a ditch.
Following up on this in correspondence with the local archaeologist, Val Turner says,
There are other Shetland examples of graveyards over brochs – Cullingsbrough, Bressay is a classic example; the excavations at Upper Scalloway another. There are also examples of early chapels known under mounds such as the mound in the graveyard at Norwick, Unst. There is also a local folklore suggestion that this is the site of a longship burial. I think this is likely to be local wishful thinking although it cannot be fully discounted.
LiDAR data is available for mainland Shetland from Lerwick down to Sumburgh Head. The data is made available under an open government licence from The Scottish Remote Sensing Portal. The data was collected between 29th November 2012 and 18th April 2014 by the Scottish Environmental Protection Agency (SEPA).
The mound can be seen clearly on the LiDAR, just south of Levenwick beach, at its eastern end. Netherton itself, sits within a low area of land between 0 and 15m, set between the slopes of the Hill of Gord and Hallilee, to the west, and the low cliffs of Levenwick Ness to the east.
The mound is fabiform (bean-shaped) in plan, of which Val Turner says, “I wondered if the shape could be to do with erosion/wind direction”. It is surrounded by a stone wall and to the north and west there is a low area between it and the dunes – interpreted in the HER record as a possible ditch. Val goes on to say, “interestingly no-one has ever reported any finds which could just mean that any finds haven’t been recognisable to the graveyard team.” About 50m to the south, a second lower mound is visible on the LiDAR orientated N-S.
The main graveyard mound is an unusual shape and another possible interpretation might be that the mound was once two taller mounds that have settled into a single mound (see interpretation above). The conjoining of the mounds may have been compounded and consolidated once adopted as a burial ground. It is surprising that no structural remains have been reported. There have been a number of local, high profile excavations of settlements buried in sand (Scatness, Jarlshof, etc) so, it would be likely, that if any structural remains had been uncovered on the Netherton mound, these would have been reported or, at the very least, there would be anecdotal accounts of their existence. It is possible that the absence of reported structural remains hints at the mounds not being settlement mounds but burial mounds. The excavated area to the north and west shows no sign of continuing around the mound. Instead, the form, as shown on the LiDAR, could equally be interpreted as a quarry pit excavated into the back of the dunes. An encircling ditch, even backfilled, would likely show as at least a shallow depression. There is no evidence for this on the sections.
The question is, is there something built or buried under the mound? Geophysics would seem like the obvious tool to use to attempt to answer this question.