Alport Castles

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Alport Castles
Tower alport castles 741794 e344ef7f.jpg
One of the outcrops known as "The Tower"
Derbyshire UK location map.svg
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Alport Castles
Location in Derbyshire
Coordinates: 53°25′15″N1°47′18″W / 53.4209°N 1.7884°W / 53.4209; -1.7884 Coordinates: 53°25′15″N1°47′18″W / 53.4209°N 1.7884°W / 53.4209; -1.7884
Location Derbyshire, England, UK

The Alport Castles are a landslip feature in the Peak District National Park in Derbyshire. At over half a mile long, it is thought to be the largest landslide in the United Kingdom. [1] 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 castle.

Contents

The Alport Castles are on the eastern side of the River Alport valley, [2] part of the National Trust's High Peak Estate; they lie north of the Snake Pass and north-west of Ladybower Reservoir.

Formation

300 million years ago, the area now known as the Peak District was part of a river delta that flowed into the sea. [1] 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 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 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. [2] A further possibility is that a valley glacier steepened the sides of the valley, leaving unstable slopes that failed after the glacier melted, causing the landslide. [2] 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. [3]

Today

The rock faces and cliffs are unstable and unsuitable for climbing and scrambling; however, the site is accessible along some well-trodden public rights of way, and is a popular site for walkers. [1]

The site is also of interest for birdwatchers, as both ravens and peregrine falcons have been known to nest on the crags. [1]

The remote Alport Castles Farm lies on the River Alport below the site. This is the farm where the suffragette Hannah Mitchell was born in 1871 and brought up. [4]

Related Research Articles

Derbyshire Ceremonial county in East Midlands, England

Derbyshire is a county in the East Midlands of England. It includes much of the Peak District National Park, the southern end of the Pennine range of hills and part of the National Forest. It borders Greater Manchester to the north-west, West Yorkshire to the north, South Yorkshire to the north-east, Nottinghamshire to the east, Leicestershire to the south-east, Staffordshire to the west and south-west and Cheshire to the west. Kinder Scout, at 636 metres (2,087 ft), is the highest point and Trent Meadows, where the River Trent leaves Derbyshire, the lowest at 27 metres (89 ft). The north–south River Derwent is the longest river at 66 mi (106 km). In 2003, the Ordnance Survey named Church Flatts Farm at Coton in the Elms, near Swadlincote, as Britain's furthest point from the sea. Derby is a unitary authority area, but remains part of the ceremonial county. The non-metropolitan county has 30 towns of 10,000–100,000 inhabitants, but much sparsely populated farming upland.

Mam Tor Hill near Castleton in the High Peak of Derbyshire, England

Mam Tor is a 517 m (1,696 ft) hill near Castleton in the High Peak of Derbyshire, England. Its name means "mother hill", so called because frequent landslips on its eastern face have resulted in a multitude of "mini-hills" beneath it. These landslips, which are caused by unstable lower layers of shale, also give the hill its alternative name of Shivering Mountain.

Kame Mound formed on a retreating glacier and deposited on land

A kame, or knob, is a glacial landform, an irregularly shaped hill or mound composed of sand, gravel and till that accumulates in a depression on a retreating glacier, and is then deposited on the land surface with further melting of the glacier. Kames are often associated with kettles, and this is referred to as kame and kettle or knob and kettle topography. The word kame is a variant of comb, which has the meaning "crest" among others. The geological term was introduced by Thomas Jamieson in 1874.

Conglomerate (geology) Coarse-grained clastic sedimentary rock with mainly rounded to subangular clasts

Conglomerate is a clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular gravel-size clasts. A conglomerate typically contain a matrix of finer-grained sediments, such as sand, silt, or clay, which fills the interstices between the clasts. The clasts and matrix are typically cemented by calcium carbonate, iron oxide, silica, or hardened clay.

Turbidite Geologic deposit of a turbidity current

A turbidite is the geologic 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.

Flysch Type of sedimentary rock sequence

Flysch is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones. It is deposited when a deep basin forms rapidly on the continental side of a mountain building episode. Examples are found near the North American Cordillera, the Alps, the Pyrenees and the Carpathians.

Mudrock Class of fine grained siliciclastic sedimentary rocks

Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than 116 mm and are too small to study readily in the field. At first sight, the rock types appear quite similar; however, there are important differences in composition and nomenclature.

Bouma sequence

The Bouma Sequence describes a classic set of sedimentary structures in turbidite beds deposited by turbidity currents at the bottoms of lakes, oceans and rivers.

Millstone Grit

Millstone Grit is the name given to any of a number of coarse-grained sandstones of Carboniferous age which occur in the British Isles. The name derives from its use in earlier times as a source of millstones for use principally in watermills. Geologists refer to the whole suite of rocks that encompass the individual limestone beds and the intervening mudstones as the Millstone Grit Group. The term Millstone Grit Series was formerly used to refer to the rocks now included within the Millstone Grit Group together with the underlying Edale Shale Group.

Karoo Supergroup Widespread Mesozoic stratigraphic unit in southern Africa

The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a period of about 120 million years.

Mount Meager massif Group of volcanoes in British Columbia, Canada

The Mount Meager massif is a group of volcanic peaks in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. Part of the Cascade Volcanic Arc of western North America, it is located 150 km (93 mi) north of Vancouver at the northern end of the Pemberton Valley and reaches a maximum elevation of 2,680 m (8,790 ft). The massif is capped by several eroded volcanic edifices, including lava domes, volcanic plugs and overlapping piles of lava flows; these form at least six major summits including Mount Meager which is the second highest of the massif.

River Alport

The River Alport flows for 5.6 miles (9 km) in the Dark Peak of the Peak District in Derbyshire, England. Its source is on Bleaklow, 3 miles (4.8 km) east of Glossop, from which it flows south through the Grains in the Water bog, then over gritstone below the Alport Castles landslide to Alport Bridge on the A57 Snake Pass route from Sheffield to Manchester, where it joins the River Ashop. The Ashop flows into Ladybower Reservoir about 2.5 miles (4.0 km) down the valley, which discharges via the Rivers Derwent and Trent to the North Sea. The source of the Alport is close to the Pennine watershed.

Mount Adams (New Zealand) Mountain in West Coast Region, New Zealand

Mount Adams is a mountain in the West Coast region of New Zealand's South Island. The summit is roughly 19 km south of Harihari and reaches 2,208 metres (7,244 ft) in height.

Martinsburg Formation Geologic formation in the eastern United States

The Ordovician Martinsburg Formation (Om) is a mapped bedrock unit in Pennsylvania, New Jersey, Maryland, Virginia, and West Virginia. It is named for the town of Martinsburg, West Virginia for which it was first described. It is the dominant rock formation of the Great Appalachian Valley in New Jersey (where it is called Kittatinny Valley and Pennsylvania.

Geology of Yorkshire

The Geology of Yorkshire in northern England shows a very close relationship between the major topographical areas and the geological period in which their rocks were formed. The rocks of the Pennine chain of hills in the west are of Carboniferous origin whilst those of the central vale are Permo-Triassic. The North York Moors in the north-east of the county are Jurassic in age while the Yorkshire Wolds to the south east are Cretaceous chalk uplands. The plain of Holderness and the Humberhead levels both owe their present form to the Quaternary ice ages. The strata become gradually younger from west to east.

The geology of Monmouthshire in southeast Wales largely consists of a thick series of sedimentary rocks of different types originating in the Silurian, Devonian, Carboniferous, Triassic and Jurassic periods.

Harthill Moor Hill in the Peak District of England

Harthill Moor is a small upland area in the Derbyshire Peak District of central and northern England, lying between Matlock and Bakewell near the villages of Birchover and Elton. The moor is within the southern portion of Harthill civil parish. Its highest point is 272 metres (892 ft) above sea level. The River Bradford flows along the northern edge of the moor past Youlgreave and into the River Lathkill at Alport. Harthill Moor is a rich prehistoric landscape with several protected Scheduled Ancient Monuments.

Glaciofluvial deposits Sediments/deposits formed from ice sheets or glaciers

Glaciofluvial deposits or Glacio-fluvial sediments consist of boulders, gravel, sand, silt and clay from ice sheets or glaciers. They are transported, sorted and deposited by streams of water. The deposits are formed beside, below or downstream from the ice. They include kames, kame terraces and eskers formed in ice contact and outwash fans and outwash plains below the ice margin. Typically the outwash sediment is carried by fast and turbulent fluvio-glacial meltwater streams, but occasionally it is carried by catastrophic outburst floods. Larger elements such as boulders and gravel are deposited nearer to the ice margin, while finer elements are carried farther, sometimes into lakes or the ocean. The sediments are sorted by fluvial processes. They differ from glacial till, which is moved and deposited by the ice of the glacier, and is unsorted.

The geology of the Peak District National Park in England is dominated by a thick succession of faulted and folded sedimentary rocks of Carboniferous age. The Peak District is often divided into a southerly White Peak where Carboniferous Limestone outcrops and a northerly Dark Peak where the overlying succession of sandstones and mudstones dominate the landscape. The scarp and dip slope landscape which characterises the Dark Peak also extends along the eastern and western margins of the park. Although older rocks are present at depth, the oldest rocks which are to be found at the surface in the national park are dolomitic limestones of the Woo Dale Limestone Formation seen where Woo Dale enters Wye Dale east of Buxton.

Oeschinensee and Kandertal landslides

The area of Oeschinen Lake and Kander river valley in Switzerland have been subject of multiple large landslides during the Holocene. Both the number and timing of landslides is controversial, with the most recent estimates stating that the large Kander landslide occurred about 3,210 years ago and the smaller Oeschinen Lake landslide 2,300 years ago. Both may have been caused by earthquakes, and the latter landslide generated the Oeschinen Lake. More recent landslides have occurred, and unstable rock masses occur in the landslide area.

References

  1. 1 2 3 4 "Peak District: Alport Castles". National Trust. Archived from the original on 14 June 2013. Retrieved 3 May 2013.
  2. 1 2 3 "Peakland Heritage: Alport Castles". Archived from the original on 29 October 2007. Retrieved 3 May 2013.
  3. Cooper, R.G. (2007). Mass Movements in Great Britain (PDF). Geological Conservation Review Series. Peterborough: JNCC. p. 20. ISBN   978 1 86107 481 2 . Retrieved 9 February 2018.
  4. "Suffragettes". Peakland Heritage. Archived from the original on 25 April 2016. Retrieved 9 February 2018.