A prehistoric site at Hadsel, Vesterålen, north Norway

Hadsel is in an area dominated by magnetite-rich bedrock. The superficial deposits therefore contain large quantities of boulders and stones of rock types which emit a relatively high magnetic signal that can lead to confusing magnetic 'noise', but may also reveal hidden patterns. Gradiometer mapping near Hadsel Church has revealed prehistoric structures marked by accumulations of stones, but also evidence that these factors conflict with each other. The mapping was concentrated in three areas:

  1. Near the sea, where there are traces of Iron Age and Medieval boathouses
  2. A flat area with prehistoric graves just north of the churchyard and a farm mound
  3. A tri-radial cairn with a central standing stone just east of the main road
Because farming has ceased, the area is now becoming heavily overgrown.

Area 1
Before the gradiometer mapping began, only two boathouses had been recognised, but some indistinct fragments of walls indicated that several more might be present. Gradiometer scanning and mapping have now helped to reveal traces of perhaps as many as 12 boathouses in two rows. They partly show up in the form of back walls (in the northern row), and partly through the systematising of some accumulations of stones just to the south. East of the boathouse labelled no. 12 is what appears to be a strip of former shore cleared of stones so that boats could be drawn up from the sea. This is about 10 m from the present shoreline.

The present height of the boathouses above sea level, compared with the estimated rate of postglacial sea-level rise, indicates that the boathouses range in age from the earliest Iron Age to the Middle Ages (ca. 2500-800 BP).


Area 2
This map shows the result of the gradiometer mapping of a 60 x 30 m large area. The eastern part is dominated by a large stone setting (marked A). It measures approximately 22 x 22 m in diameter, but is somewhat damaged, particularly in the north. A small trial trench confirmed the interpretation. Anomalies further west indicate two possible prehistoric graves (B) and perhaps a stone ring (C). D marks the margin of a large Medieval farm mound.

Area 3
A large tri-radial cairn (common in parts of Scandinavia) and a boat-shaped cairn are obvious features on a strandline between the main road and a wooded slope down towards the boathouses further east. Gradiometer mapping, however, revealed several hidden surprises. It showed that it is mostly the eastern arm and the southwestern arm that are distinct, along with the central part of the cairn, with its large standing stone in the middle (blue on the gradiometer map). The northwestern arm and the large boat-shaped cairn (A) are scarcely revealed in the magnetic measurements, probably due to poor magnetic contrast with their immediate surroundings. On the other hand, where there is no surface structure, a broad, arm-like, linear anomaly runs NNE from the standing stone.

The northern end of a boat-shaped cairn (A) can be seen at the bottom right in the figure below. Red markings on the lowermost picture show how the structures appear on the surface.