The Alport Castles are a

landslip Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslide ...

feature in the Peak District National Park in

Derbyshire Derbyshire ( ) is a ceremonial county in the East Midlands of England. It borders Greater Manchester, West Yorkshire, and South Yorkshire to the north, Nottinghamshire to the east, Leicestershire to the south-east, Staffordshire to the south a ...

. At over half a mile long, it is thought to be the largest landslide in the United Kingdom. The name "castles" comes from the debris from the landslide, which has produced several gritstone mounds that tower over the valley and appear from the distance to look like castles. Viewed from a distance the largest of these, the "Tower", resembles a full-scale

motte and bailey A motte-and-bailey castle is a European fortification with a wooden or stone keep situated on a raised area of ground called a motte, accompanied by a walled courtyard, or bailey, surrounded by a protective ditch and palisade. Relatively easy ...

castle A castle is a type of fortification, fortified structure built during the Middle Ages predominantly by the nobility or royalty and by Military order (monastic society), military orders. Scholars usually consider a ''castle'' to be the private ...

. The Alport Castles are on the eastern side of the River Alport valley, part of 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 ...

High Peak Estate The High Peak Estate is an area of Pennines, Pennine moorland in the ownership of the National Trust in the Dark Peak area of Derbyshire, England. The National Trust High Peak Estate is to be known as the 'Dark Peak Area' from summer 2010 which ...

; they lie north of the Snake Pass and north-west of Ladybower Reservoir. Below the crags, Alport Castles Farm stands on the River Alport. Suffragette Hannah Mitchell was born at the remote farm in 1871 and grew up there.

Geology

About 300 million years ago, the area now known as the

Peak District The Peak District is an Highland, upland area in central-northern England, at the southern end of the Pennines. Mostly in Derbyshire, it extends into Cheshire, Greater Manchester, Staffordshire, West Yorkshire and South Yorkshire. It is subdivi ...

was part of a

river delta A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creat ...

that flowed into the sea. The deposits were sorted such that the finest material travelled the furthest and was deposited in the deep ocean as black shales. Further deposits accumulated on the slopes of the oceans and collapsed, resulting in

turbidite A turbidite is the geologic Deposition (geology), deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing ...

deposits. Further turbidite flows eroded into previous ones, resulting in the type of deposit seen at Alport Castle. As the delta prograded (the mouth of the river moved further out to sea), the deposits become coarser. In the Peak District this coarse material is the

gritstone Gritstone or grit is a hard, coarse-grained, siliceous sandstone. This term is especially applied to such sandstones that are quarried for building material. British gritstone was used for millstones to mill flour, to grind wood into pulp for ...

that caps high points, protecting them from erosion. The exact cause of the landslide is still debated. One theory is that the soft shales below are too weak to support the weight of the heavy sandstone above and collapse under it, or that, because water can run through gritstone but not shale rock, trapped water may have "lubricated" the rock to the point where one layer slid over another, causing the landslide. A further possibility is that a valley

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

steepened the sides of the valley, leaving unstable slopes that failed after the glacier melted, causing the landslide. However, immediately upstream is a normal river valley so any glacier would have been small. Alport Castles has been selected for geological conservation as one of the most significant landslips in Britain. The rock faces and cliffs are unstable and unsuitable for climbing and scrambling. The site is popular with walkers.

Fauna

The crags are used for nesting by

raven A raven is any of several large-bodied passerine bird species in the genus '' Corvus''. These species do not form a single taxonomic group within the genus. There is no consistent distinction between crows and ravens; the two names are assigne ...

s and

peregrine falcons The peregrine falcon (''Falco peregrinus''), also known simply as the peregrine, is a cosmopolitan bird of prey (raptor) in the family Falconidae renowned for its speed. A large, crow-sized falcon, it has a blue-grey back, barred white underpa ...

References

External links

* {{Authority control Landslides in the United Kingdom Peak District