Boiling mound

A burnt mound is an archaeological feature consisting of a mound of shattered stones and charcoal, normally with an adjacent hearth and trough. The trough could be rock-cut, wood-lined or clay-lined to ensure it was watertight. Radiocarbon dates vary quite widely, the earliest being late Neolithic, with clusters of dates between 1900–1500 BC and 1200–800 BC, with some outliers in the Iron Age. There are also some dates that go into the early Medieval period. The technology used at burnt mounds has much greater antiquity and is found from the palaeolithic onwards.

The shattered rock fragments are thought to be the remains of stones heated in fires, which were used to heat water for cooking, bathing, dyeing or leather treatment. The shattering of the rock appears to have been the result of thermal shock when the heated stones were dropped into liquid, normally believed to be water. The mound is assumed to result from the periodic clearing out of the trough, with the stone fragments and charcoal being cast up into a mound. The mound is frequently a crescent shape, which is seen as being the result of the upcast.

The vast majority of burnt mounds are found in the uplands of Britain, and in Ireland where they are called fulachtaí fia. Recognised from the nineteenth century onwards, they attracted little significant interest until the 1980s. In Ireland they are often found in low-lying ground close to water. In Britain, they appeared to have a distribution pattern confined to the higher ground. However, this may be illusory, as examples have been found at lower altitudes during linear route excavations. The reason that they had not been recognised before was that the mounds have been ploughed out, although the trough may partially survive and there will be layers of the burnt mound material surviving as a spread of material. The mixture of burnt and shattered rock with charcoal, labelled as burnt mound material, is found on occasion without the trough. There are settlement sites on Orkney, where the burnt mound material is found as thick layers , but there is no trough to explain the shattering of the rocks.

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