Black Down is a hill on the South Dorset Ridgeway about north-northeast of the village of Portesham in the county of

Dorset Dorset ( ; Archaism, archaically: Dorsetshire , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by Somerset to the north-west, Wiltshire to the north and the north-east, Hampshire to the east, t ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

and around from the coast. The treeless summit of Black Down is a popular viewing point, crowned by the high Hardy Monument built in 1844 in memory of Vice-Admiral Sir Thomas Masterman Hardy who was

Admiral Nelson Horatio Nelson, 1st Viscount Nelson, 1st Duke of Bronte ( – 21 October 1805) was a Royal Navy officer whose leadership, grasp of strategy and unconventional tactics brought about a number of decisive British naval victories during the French ...

's Flag Captain at the

Battle of Trafalgar The Battle of Trafalgar was a naval engagement that took place on 21 October 1805 between the Royal Navy and a combined fleet of the French Navy, French and Spanish Navy, Spanish navies during the War of the Third Coalition. As part of Na ...

. From the top there are views of the Fleet and

Chesil Beach Chesil Beach (also known as Chesil Bank) in Dorset, England, is one of three major shingle beach structures in Britain.A. P. Carr and M. W. L. Blackley, "Investigations Bearing on the Age and Development of Chesil Beach, Dorset, and the Associ ...

as well as the South Dorset Downs. On a fine day

The Needles The Needles are a row of three stacks of chalk that rise about out of the sea off the western extremity of the Isle of Wight in the English Channel, United Kingdom, close to Alum Bay and Scratchell's Bay, and part of Totland, the weste ...

may be visible, some 50 miles away.''Hardy's Monument''
at www.worldheritagecoast.net. Accessed on 26 Mar 2013. The site is owned by the

National Trust The National Trust () is a heritage and nature conservation charity and membership organisation in England, Wales and Northern Ireland. The Trust was founded in 1895 by Octavia Hill, Sir Robert Hunter and Hardwicke Rawnsley to "promote the ...

. The

heathland A heath () is a shrubland habitat found mainly on free-draining infertile, acidic soils and is characterised by open, low-growing woody vegetation. Moorland is generally related to high-ground heaths with—especially in Great Britain—a coole ...

area around the monument was in 1984 designated a

Site of Special Scientific Interest A Site of Special Scientific Interest (SSSI) in Great Britain, or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland, is a conservation designation denoting a protected area in the United Kingdom and Isle ...

, when the

Nature Conservancy Council The Nature Conservancy Council (NCC) was a United Kingdom government agency responsible for designating and managing National Nature Reserves and other nature conservation areas in Great Britain between 1973 and 1991 (it did not cover Northern ...

decided that the geology of the area was very rare.

Geology

Geologically, Black Down is the western tip of the Bagshot gravel beds. The gravel beds extend to the east as far as London. The ground around the monument is pitted with various holes and craters. Many of these are dolines or swallow holes. These are formed when rain falls on the highly acidic

topsoil Topsoil is the upper layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Description Topsoil is composed of mineral particles and organic mat ...

. The water increases in acidity as it percolates through the topsoil then dissolves the underlying chalk. Eventually there is nothing but topsoil above the caverns so formed and the familiar shape of a doline is created when the topsoil collapses into the cavern beneath. Dolines are usually shaped like a teardrop cut in half vertically and laid down horizontally. Within of the monument there are three dolines which were formed by the chalk being dissolved in a vertical fissure in its structure. These dolines are vertically sided and are shaped like wells. The two which opened up in 1956 are some deep. The one which opened in 2006 is not quite vertical and its depth is unknown.

Gallery

File:Road from Martinstown to Black Down - geograph.org.uk - 1366394.jpg, Road from Martinstown to Black Down (far right)

References

{{Reflist Hills of Dorset