The Vale of Clwyd ( cy, Dyffryn Clwyd) is a tract of low-lying ground in the

county A county is a geographic region of a country used for administrative or other purposes Chambers Dictionary, L. Brookes (ed.), 2005, Chambers Harrap Publishers Ltd, Edinburgh in certain modern nations. The term is derived from the Old French ...

Denbighshire Denbighshire ( ; cy, Sir Ddinbych; ) is a county in the north-east of Wales. Its borders differ from the historic county of the same name. This part of Wales contains the country's oldest known evidence of habitation – Pontnewydd (Bontnewy ...

in north-east

Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...

. The Vale extends south-southwestwards from the coast of the

Irish Sea The Irish Sea or , gv, Y Keayn Yernagh, sco, Erse Sie, gd, Muir Èireann , Ulster-Scots: ''Airish Sea'', cy, Môr Iwerddon . is an extensive body of water that separates the islands of Ireland and Great Britain. It is linked to the C ...

for some 20 miles (about 30 km) forming a triangle of low ground bounded on its eastern side by the well-defined

scarp Scarp may refer to: Landforms and geology * Cliff, a significant vertical, or near vertical, rock exposure * Escarpment, a steep slope or long rock that occurs from erosion or faulting and separates two relatively level areas of differing elevatio ...

of the Clwydian Range and to the west by numerous low hills. The

River Clwyd The River Clwyd ( Welsh: ''Afon Clwyd'') is a river in Wales that rises in the Clocaenog Forest () northwest of Corwen. Its total length is . It flows due south until, at Melin-y-wig, it veers north-eastwards, tracking the A494 and passing ...

(Welsh: ) which rises within Clocaenog Forest, southwest of Denbigh, runs the full length of the vale. It is joined by the two major left bank tributaries of the River Clywedog (Welsh: ) and

River Elwy The River Elwy (''Afon Elwy'' in Welsh) is a river in Wales forming a tributary to the River Clwyd. The source of the river is sometimes said to be on the northern flank of Moel Seisiog, south-east of Llanrwst, at Ordnance Survey grid refer ...

(Welsh: ) and the smaller right bank tributary of the River Wheeler (Welsh: ).

History

Dyffryn Clwyd was a

cantref A cantref ( ; ; plural cantrefi or cantrefs; also rendered as ''cantred'') was a medieval Welsh land division, particularly important in the administration of Welsh law. Description Land in medieval Wales was divided into ''cantrefi'', which wer ...

of Medieval Wales, and from 1282 was a marcher lordship.

Settlement and administration

At its seaward end are the coastal resorts of Kinmel Bay (Welsh: ),

Rhyl Rhyl (; cy, Y Rhyl, ) is a seaside town and community in Denbighshire, Wales. The town lies within the historic boundaries of Flintshire, on the north-east coast of Wales at the mouth of the River Clwyd ( Welsh: ''Afon Clwyd''). To the we ...

and

Prestatyn Prestatyn is a seaside town and community in Denbighshire, Wales. Historically a part of Flintshire, it is located on the Irish Sea coast, to the east of Rhyl. Prestatyn has a population of 19,085, History Prehistory There is evidence that ...

whilst the town of

Abergele Abergele (; ; ) is a market town and community, situated on the north coast of Wales between the holiday resorts of Colwyn Bay and Rhyl, in Conwy County Borough and in the historic county of Denbighshire. Its northern suburb of Pensarn lies on ...

and city of

St Asaph St Asaph (; cy, Llanelwy "church on the Elwy") is a city and community on the River Elwy in Denbighshire, Wales. In the 2011 Census it had a population of 3,355, making it the second-smallest city in Britain in terms of population and urban ...

(Welsh: ) lie just inland. The other principal towns of the vale are

Denbigh Denbigh (; cy, Dinbych; ) is a market town and a community in Denbighshire, Wales. Formerly, the county town, the Welsh name translates to "Little Fortress"; a reference to its historic castle. Denbigh lies near the Clwydian Hills. History ...

(Welsh: ) and

Ruthin Ruthin ( ; cy, Rhuthun) is a market town and community in Denbighshire, Wales, in the south of the Vale of Clwyd. It is Denbighshire's county town. The town, castle and St Peter's Square lie on a hill, skirted by villages such as Pwllglas ...

(Welsh: ), also Rhuddlan. Most of the area falls within the modern administrative county (and

unitary authority A unitary authority is a local authority responsible for all local government functions within its area or performing additional functions that elsewhere are usually performed by a higher level of sub-national government or the national governmen ...

) of

and a portion is in Conwy County Borough; much of it lies within the Vale of Clwyd UK Parliamentary constituency.

Geology

The Vale of Clwyd is a

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsiden ...

which takes the form of a

half-graben A half-graben is a geological structure bounded by a fault along one side of its boundaries, unlike a full graben where a depressed block of land is bordered by parallel faults. Rift and fault structure A rift is a region where the lithosphere ...

whose eastern margin is marked by the Vale of Clwyd Fault. Like the Cheshire Basin further to its east, it is mostly floored by thick deposits of

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...

and

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicat ...

. Around St Asaph, late

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...

Coal Measures In lithostratigraphy, the coal measures are the coal-bearing part of the Upper Carboniferous System. In the United Kingdom, the Coal Measures Group consists of the Upper Coal Measures Formation, the Middle Coal Measures Formation and the Lower Coa ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology.' ...

s and sandstones occur. The area was overrun by ice during the

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

s whose legacy is a covering of

glacial till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

across the area and a swarm of drumlins along the western edge of the vale.

Alluvium Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...

is encountered across the

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

s of the River Clwyd and its tributaries.British Geological Survey, 1:50K map sheets 95 'Rhyl' & 107 'Denbigh'

References

{{DEFAULTSORT:Vale Of Clwyd Geology of Wales Sedimentary basins of Europe Valleys of Denbighshire Rifts and grabens