Science Fair Project Encyclopedia
Silbury Hill, part of the complex of Neolithic monuments around Avebury in Wiltshire (which includes the West Kennet Long Barrow), is the tallest prehistoric man-made mound in Europe and one of the world's largest.
Composed principally of chalk excavated from the surrounding area, the mound stands 130 feet (40 metres) high, and covers about 5 acres (2 hectares). It is a display of immense technical skill and prolonged control over labour and resources. Archaeologists calculate that Silbury Hill was built about 4600 years ago and that it took 18 million man-hours to dump and shape 248,000 cubic metres (8.75 million ft³) of earth on top of a natural hill.
The base of the monument is 167m (550ft) in diameter and it is perfectly round. Its summit is flat-topped and 30m (100ft) wide. We know that the construction took two phases: soon after work was started on phase 2, a re-design was ordered, and the mound enlarged.
The second phase involved heaping further more chalk on top of the core, using material excavated from an encircling ditch. At some stage during this process then builders elected to backfill the ditch and concentrate on increasing the size of the mound to its present height using material from elsewhere.
Investigations at Silbury
There have been several excavations of the mound and William Stukeley wrote that a skeleton and bridle had been discovered during tree planting on the summit in 1723. It is probable that this was a later, secondary burial however. The first purposeful excavation when a team of Cornish miners led by the Duke of Northumberland sunk a shaft from top to bottom in 1776. This was followed in 1849 when a tunnel was dug from the edge into the centre. Others were held in 1867, 1886 and William Flinders Petrie investigated the hill after the First World war. In 1968-70 professor Richard Atkinson undertook work at Silbury in front of BBC television cameras. This last work revealed most of the environmental evidence known about the site including the remains of winged ants which indicate Silbury was begun in August.
Atkinson dug numerous trenches at the site and reopened the 1849 tunnel, finding material suggesting a Neolithic date although none of his radiocarbon dates are considered reliable by modern standards. He argued that the hill was constructed in steps, each tier being filled in with packed chalk, and then smoothed off or weathered into a slope. Others have identified a spiralling path climbing to the top and prefer to see the construction as being more incremental with the benefit of also providing a processional route to the summit.
Few prehistoric artefacts have ever been found on Silbury Hill: at its core there is only clay, flints, turf, moss, topsoil, gravel, freshwater shells, mistletoe, oak, hazel, sarsen stones, ox bones, and antler tines. Roman and medieval items have been found on and around the site since the nineteenth century and it seems that the hill was reoccupied by later peoples.
In 2000, a collapse of the 1776 excavation shaft caused a hole to form in the top of the hill. English Heritage undertook a seismic survey of the hill to identify the damage caused by earlier excavations and determine the hill's stability. Repairs were undertaken though the site remains closed to the public. English Heritage's archaeologists also excavated two further small trenches as part of the remedial work and made the important discovery of an antler fragment, the first from a secure context at the site. This produced a reliable radiocarbon date of c. 2490-2340 BC, dating the second mound convincingly to the Late Neolithic. Other recent work has focused on the role of the surrounding ditch which may not have been a simple source of chalk for the hill but a purposeful water-filled barrier placed between the hill and the rest of the world.
The purpose of Silbury
Moses B.Cotworth , at the beginning of this century, stated that Silbury was a giant sundial to determine seasons and the true length of the year. More recently, the writer Michael Dames has identified Silbury Hill as the winter goddess, but he finally acknowledges that the monument remains a stupendous enigma.
The exact purpose of the hill is unknown. According to legend, this is the last resting place of King Sil , sitting on a fabled golden horse. Another legend states that the mound holds a lifesize solid gold statue of King Sil and yet a third, that the Devil was carrying an apron of soil to drop on the citizens of Marlborough, but he was stopped by the priests of nearby Avebury.
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