![Geologic map Wales & SW England EN](https://upload.wikimedia.org/wikipedia/commons/4/48/Geologic_map_Wales_%26_SW_England_EN.svg)
The geology of Wales is complex and varied; its study has been of considerable historical significance in the development of
geology as a science. All
geological periods
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochron ...
from the
Cryogenian (late
Precambrian) to the
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
are represented at outcrop, whilst younger
sedimentary rock
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
s occur beneath the seas immediately off the Welsh coast. The effects of two mountain-building episodes have left their mark in the
faulting
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
and
folding
Fold, folding or foldable may refer to:
Arts, entertainment, and media
* ''Fold'' (album), the debut release by Australian rock band Epicure
* Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot
*Abov ...
of much of the
Palaeozoic rock sequence.
Superficial deposits
Superficial deposits (or surficial deposits) refer to geological deposits typically of Quaternary age (less than 2.6 million years old). These geologically recent unconsolidated sediments may include stream channel and floodplain deposits, beach ...
and
landforms created during the present
Quaternary period by water and ice are also plentiful and contribute to a remarkably diverse landscape of mountains, hills and coastal plains.
Wales' modern character derives in substantial part from the exploitation of its diverse mineral wealth;
slate in
Snowdonia
Snowdonia or Eryri (), is a mountainous region in northwestern Wales and a national park of in area. It was the first to be designated of the three national parks in Wales, in 1951.
Name and extent
It was a commonly held belief that the na ...
,
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
in the
South Wales Valleys and
metal ores in
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
and mid Wales, to name but three. Wales' geology influences farming practices and building stone choices but also planning of developments which must take into account ground stability and liability to flooding -
geohazard
A geologic hazard or geohazard is an adverse geology, geologic condition capable of causing widespread damage or loss of property and life. These hazards are geological and environmental conditions and involve long-term or short-term geological ...
s which an appreciation of the geology can help deal with.
History of geological study
South Wales has a written record of geological interest going back to the 12th century when
Giraldus Cambrensis
Gerald of Wales ( la, Giraldus Cambrensis; cy, Gerallt Gymro; french: Gerald de Barri; ) was a Cambro-Norman priest and historian. As a royal clerk to the king and two archbishops, he travelled widely and wrote extensively. He studied and taugh ...
noted pyritous
shales near
Newport.
George Owen in 1603 correctly identified the stratigraphic relationship between the Carboniferous Limestone and the Coal Measures. Some of the first published representations of
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s were those of fossil plants taken from the
coal measures near
Neath (Gibson late 17th century).
In the mid-19th century, two prominent geologists,
Roderick Murchison and
Adam Sedgwick used their studies of the geology of Wales to establish certain principles of
stratigraphy and
palaeontology. They did fundamental work on the
Old Red Sandstone
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...
but are remembered more for their work on the lower
Palaeozoic sequence. It was Sedgwick who established the
Cambrian system and Murchison first described the
Silurian, naming it for the ancient
Silures tribe which occupied mid Wales. An overlap between the two systems as mapped led eventually to protracted dispute between the two erstwhile collaborators. After their deaths,
Charles Lapworth
Charles Lapworth FRS FGS (20 September 1842 – 13 March 1920) was a headteacher and an English geologist who pioneered faunal analysis using index fossils and identified the Ordovician period.
Biography
Charles Lapworth was born at Faring ...
erected the Ordovician system (again named for an ancient tribe of northwest Wales, the
Ordovices), to account for the sequence of rocks at the heart of the controversy.
More recently two locations in mid Wales have been selected to globally define stages of the Silurian period. Cefn-cerig Road near Cefn-cerig Farm,
Llandovery
Llandovery (; cy, Llanymddyfri ) is a market town and community in Carmarthenshire, Wales. It lies on the River Tywi and at the junction of the A40 and A483 roads, about north-east of Carmarthen, north of Swansea and west of Brecon.
Hi ...
, is the location of the
Global Boundary Stratotype Section and Point
A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted b ...
(GSSP) which marks the boundary between the
Aeronian
In the geologic timescale, the Aeronian is an age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that began 440.8 ± 1.2 Ma and ended 438.5 ± 1.1 Ma (million years ago). The Aeronian Age succeeds ...
and
Telychian
In the geologic timescale, the Telychian is the age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon. The Telychian Age was between 438.5 ± 1.2 million years ago (Ma) and 433.4 ± 0.8 Ma. The Telych ...
stages of the
Silurian period on the
geologic time scale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochrono ...
. Similarly Trefawr Track, a forestry road north of Cwm-coed-aeron Farm, Llandovery, is the location of the GSSP marking the boundary between the
Rhuddanian
In the geologic timescale, the Rhuddanian is the first age of the Silurian Period and of the Llandovery Epoch. The Silurian is in the Paleozoic Era of the Phanerozoic Eon. The Rhuddanian Age began 443.8 ± 1.5 Ma and ended 440.8 ± 1.2 Ma (mi ...
and
Aeronian
In the geologic timescale, the Aeronian is an age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that began 440.8 ± 1.2 Ma and ended 438.5 ± 1.1 Ma (million years ago). The Aeronian Age succeeds ...
stages. Both GSSPs were ratified in 1984. :''See main articles on
Cefn-cerig Road and
Trefawr Track
Trefawr Track, a forestry road north of Cwm-coed-Aeron Farm, Llandovery, Wales, is the location of the Global Boundary Stratotype Section and Point (GSSP) which marks the boundary between the Rhuddanian and Aeronian stages of the Silurian period ...
.''
Precambrian
Late
Precambrian rocks are widespread on
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
,
Llŷn and
Arfon with other, more restricted occurrences in north
Pembrokeshire
Pembrokeshire ( ; cy, Sir Benfro ) is a Local government in Wales#Principal areas, county in the South West Wales, south-west of Wales. It is bordered by Carmarthenshire to the east, Ceredigion to the northeast, and the rest by sea. The count ...
,
Radnorshire
, HQ = Presteigne
, Government = Radnorshire County Council (1889–1974) Radnorshire District Council (1974–1996)
, Origin =
, Status = historic county, administrative county
, Start ...
and
Carmarthenshire
Carmarthenshire ( cy, Sir Gaerfyrddin; or informally ') is a county in the south-west of Wales. The three largest towns are Llanelli, Carmarthen and Ammanford. Carmarthen is the county town and administrative centre. The county is known as ...
. The often intensive
metamorphism
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chem ...
which these originally
volcanic
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates a ...
and sedimentary rocks have been subjected to and their generally
faulted relationship to neighbouring rocks has meant that geologists’ understanding of them has been limited. The majority lie on or close to the margins of
terrane
In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its own ...
s, blocks of the Earth's crust which have had differing geological histories before assuming their present configuration. However, in recent years there has been a progressive elucidation of the way in which Wales’ many terranes came together during the late Precambrian and the
Palaeozoic era.
The
Stanner-Hanter Complex on the English border comprises volcanic rocks around 700 million years old which puts them within the
Cryogenian period.
Palaeozoic
Cambrian
Rocks of
Cambrian age occur most extensively in an
inlier
An inlier is an area of older rock (geology), rocks surrounded by younger rocks. Inliers are typically formed by the erosion of overlying younger rocks to reveal a limited outcrop, exposure of the older underlying rocks. Fault (geology), Faulting o ...
in
Merionethshire
, HQ= Dolgellau
, Government= Merionethshire County Council (1889-1974)
, Origin=
, Status=
, Start= 1284
, End=
, Code= MER
, CodeName= ...
where the
up-arched rocks of the
Harlech Dome
The Harlech Dome is a geological dome in southern Snowdonia in north Wales. It extends approximately from Blaenau Ffestiniog in the north to Tywyn in the south, and includes Harlech, The Rhinogydd, Barmouth and Cadair Idris.
The geological lay ...
form the
Rhinogydd
The Rhinogydd (a Welsh plural form, often anglicised as Rhinogs and also known by the alternative Welsh plural Rhinogau) are a range of mountains located east of Harlech in North Wales. The name ''Rhinogydd'' derives from the names of two of the ...
. The
Harlech Grits Group comprises
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 silicates) ...
s,
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
greywacke
Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...
s forms the eroded core of the dome and within this sequence it is specifically the greywackes of the 'Rhinog Formation' which provides the higher hills. Cambrian rocks are also to be found in north Pembrokeshire,
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
and
Llŷn.
Ordovician
The
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
period gave rise to a sequence of sedimentary rocks which stretch from Pembrokeshire eastwards through Carmarthenshire up the
Vale of Towy and which are intricately intermixed with those of the succeeding period northwards to the
Vale of Conwy. In Snowdonia many Ordovician
volcanic rocks
Volcanic rock (often shortened to volcanics in scientific contexts) is a Rock (geology), rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of Volcano, volcanic origin. Like all rock types, ...
give rise to a more rugged landscape than elsewhere in the country. Snowdon itself is largely formed of volcanic ash (
tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...
) with some sedimentary rock and igneous
intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
s folded into a syncline.
Cadair Idris
Cadair Idris or Cader Idris is a mountain in the Meirionnydd area of Gwynedd, Wales. It lies at the southern end of the Snowdonia National Park near the town of Dolgellau. The peak, which is one of the most popular in Wales for walkers and hiker ...
is also largely formed of Ordovician igneous rocks.
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
and
Llŷn are also Ordovician territory. The Ordovician rocks of Wales are typically intensely faulted and folded, having been affected by the earth movements of the
Caledonian Orogeny
The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occ ...
.
A notable feature of the
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...
system is a major
downwarp known as the Welsh geosyncline.
Silurian
Rocks dating from the
Silurian period are, by one measure, the most significant for Wales’ landscape; a greater percentage of the country's land area is directly underlain by rocks of this age than any other. Much of central Wales is formed in Silurian sandstones and mudstones as is the more gentle landscape of central
Monmouthshire
Monmouthshire ( cy, Sir Fynwy) is a county in the south-east of Wales. The name derives from the historic county of the same name; the modern county covers the eastern three-fifths of the historic county. The largest town is Abergavenny, with ...
where the
Usk Anticline gives rise to the
Usk Inlier
The Usk Inlier is a domed outcrop of rock strata of Silurian age in Monmouthshire in south-eastern Wales. It is located in the countryside between the towns of Caerleon and Pontypool and the village of Raglan. The longer axis of the dome or ' pe ...
. In the north it is the
Ludlow
Ludlow () is a market town in Shropshire, England. The town is significant in the history of the Welsh Marches and in relation to Wales. It is located south of Shrewsbury and north of Hereford, on the A49 road which bypasses the town. The t ...
age mudstones and sandstones of the Elwy and Nantglyn Formations which form the
Clwydian Range
The Clwydian Range ( cy, Bryniau Clwyd; also known as the Clwydian Hills; or simply the Clwyds) is a series of hills in the north-east of Wales that runs from Llandegla in the south to Prestatyn in the north, the highest point being the pop ...
, and the Nantglyn Flags and
Wenlockian Denbigh Grits which form the
Denbigh Moors,
Llantysilio Mountain
: ''Both Llantysilio Mountain and Maesyrchen Mountain re-direct here.''
Moel y Gamelin is a hill in Denbighshire, North Wales, to the northwest of the town of Llangollen. It is the highest summit of a range which stretches eastwards from near ...
and the
Dee Valley around
Llangollen
Llangollen () is a town and community, situated on the River Dee, in Denbighshire, Wales. Its riverside location forms the edge of the Berwyn range, and the Dee Valley section of the Clwydian Range and Dee Valley Area of Outstanding Natural Beau ...
. In west Wales, parts of south and central
Pembrokeshire
Pembrokeshire ( ; cy, Sir Benfro ) is a Local government in Wales#Principal areas, county in the South West Wales, south-west of Wales. It is bordered by Carmarthenshire to the east, Ceredigion to the northeast, and the rest by sea. The count ...
around
Haverfordwest
Haverfordwest (, ; cy, Hwlffordd ) is the county town of Pembrokeshire, Wales, and the most populous urban area in Pembrokeshire with a population of 14,596 in 2011. It is also a community, being the second most populous community in the county, ...
and
Narberth and between
Marloes
Marloes is a village and parish in Pembrokeshire, Wales, on the Marloes Peninsula west of Milford Haven and forms the western tip of the southern shore of St Brides Bay. It is within part of the Pembrokeshire Coast National Park. The parish ...
and
Daugleddau are formed by
Llandovery
Llandovery (; cy, Llanymddyfri ) is a market town and community in Carmarthenshire, Wales. It lies on the River Tywi and at the junction of the A40 and A483 roads, about north-east of Carmarthen, north of Swansea and west of Brecon.
Histo ...
aged mudstones, sandstones and conglomerates.
The Caledonian orogeny
A long and complex series of
continental collision
In geology, continental collision is a phenomenon of plate tectonics that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains prod ...
s known collectively as the
Caledonian orogeny
The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occ ...
began in the Ordovician and continued through the Silurian into Devonian times. The effect in this area was to cause folding and faulting of the existing rock sequence, most particularly within the
Welsh Basin
The Welsh Basin was a northeast-southwest aligned back-arc depositional basin during the Cambrian, Ordovician and Silurian periods during which a considerable thickness of marine sediments was laid down in the area. To the southeast lay the Midlan ...
, a process which intensified northwards. Parts of the sequence were subjected to low grade
metamorphism
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of chem ...
, the most significant of which, from an economic point of view, would be the Cambrian and Ordovician slates of North Wales. The northeast to southwest 'grain' of much of the country was imparted at this time with a series of major fault zones persisting from that time to the present, some of which, particularly in the northwest, are believed to represent terrane boundaries. The
siliciclastic
Siliciclastic (or ''siliclastic'') rocks are clastic noncarbonate sedimentary rocks that are composed primarily of silicate minerals, such as quartz or clay minerals. Siliciclasic rock types include mudrock, sandstone, and conglomerate
Conglomera ...
deposits of the succeeding Devonian period represent in large part the rapid attrition of the extensive Caledonian Mountain belt created by the Caledonian collision.
Devonian
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
age rocks are broadly synonymous with the
Old Red Sandstone
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...
(commonly referred to as ‘the ORS’) though the lowermost ORS is late Silurian in age. The
Anglo-Welsh Basin which stretches from the border with England westwards through the
Brecon Beacons National Park
The Brecon Beacons National Park ( cy, Parc Cenedlaethol Bannau Brycheiniog) is one of three national parks in Wales, and is centred on the Brecon Beacons range of hills in southern Wales. It includes the Black Mountain (range), Black Mountain ...
into Pembrokeshire includes the larger part of this sequence. It is the sandstones and mudstones of the Lower Devonian
Brownstones
Brownstone is a brown Triassic–Jurassic sandstone that was historically a popular building material. The term is also used in the United States and Canada to refer to a townhouse clad in this or any other aesthetically similar material.
Type ...
and
Senni Formations, sometimes capped by the hard wearing sandstones of the
Plateau Beds which form such striking peaks as
Pen y Fan
Pen y Fan () is the highest peak in South Wales, situated in the Brecon Beacons National Park. At above sea-level, it is also the highest British peak south of Cadair Idris in Snowdonia. It is the highest point (county top) of the historic cou ...
and
Sugar Loaf and the dramatic scarps of the
Black Mountains and
Black Mountain. There are restricted occurrences of Devonian rocks on
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
too.
Carboniferous
The
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 ''Carbonifero ...
period is represented by extensive outcrops across South Wales from the
Wye Valley
The Wye Valley Area of Outstanding Natural Beauty (AONB; cy, Dyffryn Gwy) is an internationally important protected landscape straddling the border between England and Wales.
The River Wye ( cy, Afon Gwy) is the fourth-longest river in th ...
in the east, through the
South Wales Coalfield
The South Wales Coalfield ( cy, Maes glo De Cymru) extends across Pembrokeshire, Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent and Torfaen. It is rich in coal deposits, espec ...
, the
Vale of Glamorgan
The Vale of Glamorgan ( cy, Bro Morgannwg ), often referred to as The Vale, is a county borough in the south-east of Wales. It borders Bridgend County Borough to the west, Cardiff to the east, Rhondda Cynon Taf to the north, and the Bristol C ...
and
Gower
Gower ( cy, Gŵyr) or the Gower Peninsula () in southwest Wales, projects towards the Bristol Channel. It is the most westerly part of the historic county of Glamorgan. In 1956, the majority of Gower became the first area in the United Kingdom ...
westwards to southern
Pembrokeshire
Pembrokeshire ( ; cy, Sir Benfro ) is a Local government in Wales#Principal areas, county in the South West Wales, south-west of Wales. It is bordered by Carmarthenshire to the east, Ceredigion to the northeast, and the rest by sea. The count ...
. There are less extensive areas in northeast Wales and along the north coast into
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
where similarly aged rocks characterize the landscape. The sequence includes Carboniferous Limestone at its base, followed by coarse sandstones (The ‘
Millstone Grit’ of the north and the ‘
Twrch Sandstone
The Marros Group is the name given to a suite of rocks of Namurian age laid down during the Carboniferous Period in South Wales. These rocks were formerly known as the Millstone Grit Series but are now distinguished from the similar but geographi ...
’ of the south), then mudstones and finally the
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 Coal ...
which comprise a thick succession of
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,
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 silicates) ...
s and of course
coal seam
Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron fro ...
s.
Limestone
Though mid Wales lay
above sea level
Height above mean sea level is a measure of the vertical distance (height, elevation or altitude) of a location in reference to a historic mean sea level taken as a vertical datum. In geodesy, it is formalized as ''orthometric heights''.
The comb ...
during Carboniferous times, shallow tropical seas extended across much of north and south Wales and it was in these environments that a succession of types of limestone were deposited.
The limestone gives rise to impressive cliffed landscapes both on the coast as at the
Great Orme
The Great Orme ( cy, Y Gogarth) is a limestone headland on the north coast of Wales, north-west of the town of Llandudno. Referred to as ''Cyngreawdr Fynydd'' by the 12th-century poet Gwalchmai ap Meilyr, its English name derives from the Old N ...
in the north and at
St Govan's Head and the
Gower Peninsula
Gower ( cy, Gŵyr) or the Gower Peninsula () in southwest Wales, projects towards the Bristol Channel. It is the most westerly part of the historic county of Glamorgan. In 1956, the majority of Gower became the first area in the United Kingdom ...
in the south, and inland at the escarpments of
Eglwyseg Mountain
The Eglwyseg valley is an area to the north east of Llangollen in Denbighshire, Wales; it is within the boundaries of Llantysilio Community. The name also refers to a widely scattered hamlet in the valley.
Formerly the old township of Eglwysegl ...
near
Llangollen
Llangollen () is a town and community, situated on the River Dee, in Denbighshire, Wales. Its riverside location forms the edge of the Berwyn range, and the Dee Valley section of the Clwydian Range and Dee Valley Area of Outstanding Natural Beau ...
and
Llangattock
Llangattock ( cy, Llangatwg) is a village, community and electoral ward in the Brecon Beacons National Park in Powys, Wales. It lies in the Usk Valley just across the river from the town of Crickhowell. The Monmouthshire and Brecon Canal passe ...
hillside in the
Usk Valley.
Karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
landscapes characterize the limestone outcrop and, particularly along the ‘north crop’ of the
South Wales Coalfield
The South Wales Coalfield ( cy, Maes glo De Cymru) extends across Pembrokeshire, Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent and Torfaen. It is rich in coal deposits, espec ...
basin, where the limestone is shallowly buried beneath adjacent sandstones, extensive development of
solution hollows has taken place.
Namurian sequence
The
Namurian
The Namurian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 326 and 313 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Namurian is ...
age mudstones and sandstones which overlie/succeed the limestone give rise to rugged landscapes; typically either poorly drained moorland or else wooded gorges as in the
Waterfall Country of southern
Powys
Powys (; ) is a Local government in Wales#Principal areas, county and Preserved counties of Wales, preserved county in Wales. It is named after the Kingdom of Powys which was a Welsh succession of states, successor state, petty kingdom and princi ...
.
Coal Measures
Landscapes developed over Coal Measures rocks are extensively altered by man, as the coal and iron found within this thick sequence of rocks have long been economically important, particularly since the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. The former
coalfield
A coalfield is an area of certain uniform characteristics where coal is mined. The criteria for determining the approximate boundary of a coalfield are geographical and cultural, in addition to geological. A coalfield often groups the seams of ...
s of
Flintshire
, settlement_type = County
, image_skyline =
, image_alt =
, image_caption =
, image_flag =
, image_shield = Arms of Flint ...
,
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 ...
and
South Wales
South Wales ( cy, De Cymru) is a loosely defined region of Wales bordered by England to the east and mid Wales to the north. Generally considered to include the historic counties of Glamorgan and Monmouthshire, south Wales extends westwards ...
are witness to this period. In
South Wales
South Wales ( cy, De Cymru) is a loosely defined region of Wales bordered by England to the east and mid Wales to the north. Generally considered to include the historic counties of Glamorgan and Monmouthshire, south Wales extends westwards ...
, the Coal Measures are overlain by the thick sandstones of the
Pennant Measures
The Pennant Measures is the traditional name for a sequence of sedimentary rocks of the South Wales Coalfield. They were also referred to as the Upper Coal Measures and assigned to the Westphalian 'C' and Westphalian 'D' stages of the Carbonifero ...
which often provides craggy edges to the plateau which has been deeply dissected to form the
South Wales Valleys. The Pennant Sandstone is widely used as a building stone.
A major geological feature of the Upper Carboniferous sub-period in South Wales is the
South Wales Coalfield
The South Wales Coalfield ( cy, Maes glo De Cymru) extends across Pembrokeshire, Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent and Torfaen. It is rich in coal deposits, espec ...
syncline
In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimpose ...
. The rocks comprising this important area were laid down during the
Westphalian Age approximately 314-308 million years ago (Ma), when climatic conditions were equatorial. This Westphalian succession includes a sequence with a thickness of more than 1800 m in the west. The Coal Measures were laid down on a low-lying waterlogged plain with peat mires immediately south of an ancient geological feature known as the
Wales-London-Brabant High.
Variscan Orogeny
From late Carboniferous times, through the Permian, South Wales lay on the northern margin of the
Variscan orogen, an area affected by a complex continental collision taking place to the south. The most intensely affected rocks are those of south and central Pembrokeshire where steeply dipping and vertical strata are commonplace and multiple folding, faulting and
overthrust
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks.
Thrust geometry and nomenclature
Reverse faults
A thrust fault is a type of reverse fault that has a dip of 45 degrees or less.
If ...
ing are well seen in coastal sections. Southern Carmarthenshire and the western part of the South Wales Coalfield were affected to a lesser extent. Old
Caledonoid weaknesses such as the
Neath Disturbance
The Neath Disturbance is a geological structure which stretches across south Wales from Swansea Bay northeastwards as far as Hereford in western England. It consists of a series of both faults and associated folds which were active during the mo ...
were reactivated at this time.
Permian
Rocks dating from the
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 Paleoz ...
period occur in North Wales underlying the
Vale of Clwyd
The Vale of Clwyd ( cy, Dyffryn Clwyd) is a tract of low-lying ground in the county of Denbighshire in north-east Wales. The Vale extends south-southwestwards from the coast of the Irish Sea for some 20 miles (about 30 km) forming a triangl ...
and extend into the northeastern fringes of the country from the larger bodies of such rock in Cheshire and Shropshire. The Permo-Triassic rocks in the northeast of Wales are largely concealed by recent material deposited by rivers and the
Devensian icesheet. Thicker sequences of Permo-Triassic rock are known to underlie the Bristol Channel, Cardigan Bay and the Irish Sea off the North Wales coast.
Mesozoic
Triassic
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 period ...
sandstones form much of the coast between
Barry Barry may refer to:
People and fictional characters
* Barry (name), including lists of people with the given name, nickname or surname, as well as fictional characters with the given name
* Dancing Barry, stage name of Barry Richards (born c. 19 ...
and
Penarth
Penarth (, ) is a town and Community (Wales), community in the Vale of Glamorgan ( cy, Bro Morgannwg), Wales, exactly south of Cardiff city centre on the west shore of the Severn Estuary at the southern end of Cardiff Bay.
Penarth is a weal ...
and extend eastwards along the Monmouthshire coast to the English border at
Chepstow
Chepstow ( cy, Cas-gwent) is a town and community in Monmouthshire, Wales, adjoining the border with Gloucestershire, England. It is located on the tidal River Wye, about above its confluence with the River Severn, and adjoining the western ...
. They also occur more sporadically further west between
Ogmore-by-Sea
Ogmore-by-Sea ( Welsh: ''Aberogwr'', meaning "Mouth of the River Ogmore") is a seaside village in St Brides Major community in the Vale of Glamorgan, Wales. It lies on the western limit of the Glamorgan Heritage Coast of south Wales. The pop ...
and
Kenfig
Kenfig ( cy, Cynffig) is a village and former borough in Bridgend, Wales. It is situated inland on the north bank of the Bristol Channel, and just south-west of the M4 motorway. To the east is the town of Bridgend, at approximately , and the c ...
. There are very localized occurrences of Triassic material in Gower and south Pembrokeshire, much of it
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...
-fill of fissures in underlying Carboniferous Limestone. Triassic sandstones are also found along the border with
Cheshire
Cheshire ( ) is a ceremonial and historic county in North West England, bordered by Wales to the west, Merseyside and Greater Manchester to the north, Derbyshire to the east, and Staffordshire and Shropshire to the south. Cheshire's county t ...
and
Shropshire
Shropshire (; alternatively Salop; abbreviated in print only as Shrops; demonym Salopian ) is a landlocked historic county in the West Midlands region of England. It is bordered by Wales to the west and the English counties of Cheshire to th ...
, though most often concealed beneath recent fluvial and glacially derived material.
Jurassic
![Blue Lias cliff, Rhoose - geograph](https://upload.wikimedia.org/wikipedia/commons/a/a8/Blue_Lias_cliff%2C_Rhoose_-_geograph.org.uk_-_981193.jpg)
Rocks dating from the
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
period occur widely across the
Vale of Glamorgan
The Vale of Glamorgan ( cy, Bro Morgannwg ), often referred to as The Vale, is a county borough in the south-east of Wales. It borders Bridgend County Borough to the west, Cardiff to the east, Rhondda Cynon Taf to the north, and the Bristol C ...
. Much of the Glamorgan coast between
Ogmore-by-Sea
Ogmore-by-Sea ( Welsh: ''Aberogwr'', meaning "Mouth of the River Ogmore") is a seaside village in St Brides Major community in the Vale of Glamorgan, Wales. It lies on the western limit of the Glamorgan Heritage Coast of south Wales. The pop ...
and
Barry Barry may refer to:
People and fictional characters
* Barry (name), including lists of people with the given name, nickname or surname, as well as fictional characters with the given name
* Dancing Barry, stage name of Barry Richards (born c. 19 ...
is formed by cliffs of layered Jurassic limestone known as the
Lias
Lias may refer to:
Geology
* Lias Formation, a geologic formation in France
*Lias Group, a lithostratigraphic unit in western Europe
* Early Jurassic, an epoch
People
* Godfrey Lias, British author
* Mohd Shamsudin Lias (born 1953), Malaysian ...
. Extensive and spectacular
shore platforms have been developed e.g. near
Southerndown, as these cliffs have
retreated inland through frequent rockfall.
Cretaceous
There are no rocks of
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
age in Wales but they are known to be present within the sub-sea basins off the Welsh coast e.g.
Celtic Sea
The Celtic Sea ; cy, Y Môr Celtaidd ; kw, An Mor Keltek ; br, Ar Mor Keltiek ; french: La mer Celtique is the area of the Atlantic Ocean off the southern coast of Ireland bounded to the east by Saint George's Channel; other limits includ ...
and the
Bristol Channel
The Bristol Channel ( cy, Môr Hafren, literal translation: "Severn Sea") is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England. It extends from the lower estuary of the River Seve ...
.
Cenozoic
Palaeogene and Neogene
There is scant evidence for rocks of the
Palaeogene
The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...
and
Neogene
The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...
periods in Wales though they are known to occur offshore. The exceptions are the sequence revealed in the
Mochras
Mochras (sometimes known as ''Shell Island''), is a peninsula lying west of Llanbedr in Gwynedd, Wales. It was formed after the River Artro was diverted by the Earl of Winchelsey in 1819 from its previous course where it entered the sea to the ...
borehole on the coastal strip south of
Harlech
Harlech () is a seaside resort and community in Gwynedd, north Wales and formerly in the historic county of Merionethshire. It lies on Tremadog Bay in the Snowdonia National Park. Before 1966, it belonged to the Meirionydd District of the 197 ...
and the 'pocket deposits' where sediments fill depressions in the Carboniferous Limestone in northeast Wales. In the south, poorly
cemented sands occur sporadically in the central and western part of the Brecon Beacons National Park; these are thought to be a product of the
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
weathering of the underlying Twrch Sandstone.
Quaternary
The landscape of Wales has assumed its present shape over the last 2.6 million years i.e. during the
Quaternary period which reaches to the present day. Icesheets and valley glaciers which developed during a series of ice ages have significantly altered a landscape which had developed as rivers drained a tilted upland surface which is thought to have emerged from beneath the sea during earlier Cainozoic times.
Glacial legacy
The effects of the last (
Devensian) ice age are the most readily understood. An icesheet which at its maximum extent covered virtually all of Wales and reached as far south as Cardiff, Bridgend and Gower left in its wake suites of both erosional and depositional landforms. The
glacial cirque
A (; from the Latin word ') is an amphitheatre-like valley formed by glacial erosion. Alternative names for this landform are corrie (from Scottish Gaelic , meaning a pot or cauldron) and (; ). A cirque may also be a similarly shaped landform ...
s of Snowdonia and to a lesser extent of the Cambrian Mountains and the Brecon Beacons are well known. Many pre-existing valleys were further deepened by glacial ice. Cirque
moraine
A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...
s in the mountains and
terminal
Terminal may refer to:
Computing Hardware
* Terminal (electronics), a device for joining electrical circuits together
* Terminal (telecommunication), a device communicating over a line
* Computer terminal, a set of primary input and output dev ...
and
recessional moraines in the major valleys are the most striking depositional legacy of the glaciation. Three substantial median moraines extend beneath the waters of
Cardigan Bay
Cardigan Bay ( cy, Bae Ceredigion) is a large inlet of the Irish Sea, indenting the west coast of Wales between Bardsey Island, Gwynedd in the north, and Strumble Head, Pembrokeshire at its southern end. It is the largest bay in Wales.
Geograp ...
, parts being exposed at low
spring tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide tables ca ...
s as
Sarn Badrig,
Sarn y Bwlch and
Sarn Cynfelin.
There are too, swarms of
drumlin
A drumlin, from the Irish word ''droimnín'' ("littlest ridge"), first recorded in 1833, in the classical sense is an elongated hill in the shape of an inverted spoon or half-buried egg formed by glacial ice acting on underlying unconsolidated ...
s and a widespread plastering 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 ...
elsewhere. The greatest concentration of drumlins is in
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 ...
though there are also distinct areas around the
Severn valley
The Severn Valley is a rural area of the West Midlands region of England, through which the River Severn runs and the Severn Valley Railway steam heritage line operates, starting at its northernmost point in Bridgnorth, Shropshire and runni ...
.
Coastal deposits
Following the end of the last ice age, sea levels rose to roughly their current levels by around 6000 years ago. Forests which had become established at or below this level were destroyed though the preserved stumps of trees in growth position can still be seen in the intertidal zone in places, as can the remains of peat deposits which again had originally formed above the high-water mark. Redistribution of glacial and fluvial sands has given rise to extensive dune systems around the Welsh coast, notably at
Newborough Warren
Newborough Warren ( cy, Tywyn Niwbwrch) near the village of Newborough, Anglesey, Newborough (''Niwbwrch'') is a large dune and beach system of , approximately half of which is a conifer plantation. The whole area is designated as a Site of Speci ...
on Anglesey,
Morfa Harlech
Morfa Harlech National Nature Reserve () is a nature reserve in Wales, located north of Harlech.
The reserve reaches across expanses of open sand and sea towards Snowdonia and contains one of the two extensive sand dune systems which make up much ...
and
Morfa Dyffryn
Morfa Dyffryn beach is on the west coast of Wales, between Barmouth and Harlech in Gwynedd. This sandy beach is several miles long and is chiefly known for having an officially recognised naturist area, in length. The beach is very clean and is ...
in
Gwynedd
Gwynedd (; ) is a county and preserved county (latter with differing boundaries; includes the Isle of Anglesey) in the north-west of Wales. It shares borders with Powys, Conwy County Borough, Denbighshire, Anglesey over the Menai Strait, and C ...
and at
Pendine
Pendine ( cy, Pentywyn, "end of the dunes") is a village and community in Carmarthenshire, Wales. Situated on the northern shore of Carmarthen Bay and bordered by the communities of Eglwyscummin and Llanddowror, the population at the 2011 censu ...
and
Pembrey Burrows
Pembrey Burrows stretch from Burry Port's harbour area – a former coal port, now a marina – to Pembrey Country Park, a leisure and nature complex that is one of West Wales's leading visitor attraction.
The Burrows not only provide sanctuary of ...
in Carmarthenshire and at
Merthyr-mawr Warren and
Kenfig Burrows in
Glamorgan
, HQ = Cardiff
, Government = Glamorgan County Council (1889–1974)
, Origin=
, Code = GLA
, CodeName = Chapman code
, Replace =
* West Glamorgan
* Mid Glamorgan
* South Glamorgan
, Motto ...
.
:*''See also
Coastline of Wales''
Karstic landforms
Within the limestone areas of Wales, there have arisen
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
ic landscapes during the postglacial period, though elements of these were initiated during and even before successive ice ages.
Limestone pavement
A limestone pavement is a natural karst landform consisting of a flat, incised surface of exposed limestone that resembles an artificial pavement. The term is mainly used in the UK and Ireland, where many of these landforms have developed dis ...
s are best developed along the 'north crop' within the Brecon Beacons National Park and there are numerous sinkholes and shakeholes, together with sinks, sections of dry valley and resurgences. Cave development is extensive and includes systems such as
Ogof Ffynnon Ddu
Ogof Ffynnon Ddu ( Welsh for ''cave of the black spring''), also known informally as OFD, is a cave under a hillside in the area surrounding Penwyllt in the Upper Swansea Valley in South Wales. It is the second longest cave in Wales and the d ...
(Britain's deepest cave),
Dan-yr-ogof
Dan yr Ogof (), at the National Showcaves Centre for Wales, is a long cave system in south Wales, about north of Ystradgynlais and southwest of Brecon, in the Brecon Beacons National Park. It is the main feature of a show cave complex, which i ...
(partly showcave) and Wales' most extensive system
Ogof Draenen
Ogof Draenen (Welsh for "hawthorn cave") is, at 66 km (official figure; the true length of passage is still being revised upward, with a modern estimate of approximately 70 km), the longest cave system in Wales and the second longest in ...
.
Economic geology
Metals
Humans have mined metals and metal ores in Wales for millennia. There are
Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
workings on the
Great Orme
The Great Orme ( cy, Y Gogarth) is a limestone headland on the north coast of Wales, north-west of the town of Llandudno. Referred to as ''Cyngreawdr Fynydd'' by the 12th-century poet Gwalchmai ap Meilyr, its English name derives from the Old N ...
near
Llandudno
Llandudno (, ) is a seaside resort, town and community in Conwy County Borough, Wales, located on the Creuddyn peninsula, which protrudes into the Irish Sea. In the 2011 UK census, the community – which includes Gogarth, Penrhyn Bay, Craigsi ...
and at
Parys Mountain
Parys Mountain ( cy, Mynydd Parys) is located south of the town of Amlwch in north east Anglesey, Wales. It is the site of a large copper mine that was extensively exploited in the late 18th century. Parys Mountain is a mountain in name only, bei ...
on Anglesey.
Gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
has been obtained since pre-Roman times at places like
Dolaucothi
The Dolaucothi Gold Mines (; cy, Mwynfeydd Aur Dolaucothi) (), also known as the Ogofau Gold Mine, are ancient Roman surface and underground mines located in the valley of the River Cothi, near Pumsaint, Carmarthenshire, Wales. The gold min ...
. Lead and zinc were intensively mined in the
Cwmystwyth
Cwmystwyth (also Cwm Ystwyth, ; en, "valley of the River Ystwyth") is a village in Ceredigion, Wales near Devil's Bridge, and Pont-rhyd-y-groes.
The Ordnance Survey calculates Cwmystwyth to be the centre point of Wales (; ).
History
Dis ...
area of mid Wales and a lead mine operated at
Minera
Minera ( cy, Mwynglawdd; ) is a village and community in Wrexham County Borough, Wales. It adjoins the village of Coedpoeth.
The community, which in addition to Minera village includes a number of smaller hamlets such as Gwynfryn and New Brigh ...
near Wrexham from the
Middle Ages
In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...
until the early twentieth century. In
Victorian times
In the history of the United Kingdom and the British Empire, the Victorian era was the period of Queen Victoria's reign, from 20 June 1837 until her death on 22 January 1901. The era followed the Georgian period and preceded the Edwardi ...
the
Sygun Copper Mine was opened near
Beddgelert
Beddgelert () is a village and community in the Snowdonia area of Gwynedd, Wales. The population of the community taken at the 2011 census was 455, and includes Nantmor and Nant Gwynant. It is reputed to be named after the legendary hound ...
in
Snowdonia
Snowdonia or Eryri (), is a mountainous region in northwestern Wales and a national park of in area. It was the first to be designated of the three national parks in Wales, in 1951.
Name and extent
It was a commonly held belief that the na ...
.
Ironstone
Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be con ...
is a component of the Lower Coal Measures rock sequence and where it outcrops along the northern edge of the
South Wales Coalfield
The South Wales Coalfield ( cy, Maes glo De Cymru) extends across Pembrokeshire, Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent and Torfaen. It is rich in coal deposits, espec ...
, it was extensively worked for the production of iron and was important in the initiation of the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
in South Wales.
Slate
The slate industry of Snowdonia was once of world importance. Purple and green slates of Cambrian age were worked at vast quarries on the flanks of Snowdon and at
Bethesda,
Dinorwig
Dinorwig sometimes spelled Dinorwic ( ; ; ), is a village located high above Llyn Padarn, near Llanberis, in Wales. The name is shared with the fort of Dinas Dinorwig, also within the community of Llanddeiniolen, on a foothill from Dinorwig v ...
,
Corris
Corris is a village in the county of Gwynedd, Wales, about north of the town of Machynlleth. The village lies on the west bank of the Afon Dulas (which here forms the boundary with Powys), around that river's confluence with the Afon Deri ...
and
Blaenau Ffestiniog
Blaenau Ffestiniog is a town in Gwynedd, Wales. Once a slate mining centre in historic Merionethshire, it now relies much on tourists, drawn for instance to the Ffestiniog Railway and Llechwedd Slate Caverns. It reached a population of 12,00 ...
.
Building stone
The abundance of hard rock in Wales means that it has found use in building since the earliest times. The 'bluestones' (of Ordovician
dolerite
Diabase (), also called dolerite () or microgabbro,
is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grained ...
) which form the lintels of
Stonehenge
Stonehenge is a prehistoric monument on Salisbury Plain in Wiltshire, England, west of Amesbury. It consists of an outer ring of vertical sarsen standing stones, each around high, wide, and weighing around 25 tons, topped by connectin ...
were sourced in the
Preseli Hills
The Preseli Hills or, as they are known locally and historically, Preseli Mountains, (Welsh: ''Mynyddoedd y Preseli / Y Preselau'' , ) is a range of hills in western Wales, mostly within the Pembrokeshire Coast National Park.
The range stret ...
of Pembrokeshire around 2500 BC.
Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...
and
Iron Age
The Iron Age is the final epoch of the three-age division of the prehistory and protohistory of humanity. It was preceded by the Stone Age (Paleolithic, Mesolithic, Neolithic) and the Bronze Age (Chalcolithic). The concept has been mostly appl ...
peoples made extensive use of local materials in erecting a variety of
cairn
A cairn is a man-made pile (or stack) of stones raised for a purpose, usually as a marker or as a burial mound. The word ''cairn'' comes from the gd, càrn (plural ).
Cairns have been and are used for a broad variety of purposes. In prehis ...
s,
standing stone
A menhir (from Brittonic languages: ''maen'' or ''men'', "stone" and ''hir'' or ''hîr'', "long"), standing stone, orthostat, or lith is a large human-made upright rock (geology), stone, typically dating from the European middle Bronze Age. T ...
s and defensive works as manifest in Wales' many
hill fort
A hillfort is a type of earthwork used as a fortified refuge or defended settlement, located to exploit a rise in elevation for defensive advantage. They are typically European and of the Bronze Age or Iron Age. Some were used in the post-Roma ...
s.
Wales' many fine cathedrals, abbeys and castles have used a variety of stones in their construction; Caerbwdi Sandstone in
St David's Cathedral, Old Red Sandstone at
Llanthony Priory
Llanthony Priory ( cy, Priordy Llanddewi Nant Hodni) is a partly ruined former Augustinian priory in the secluded Vale of Ewyas, a steep-sided once-glaciated valley within the Black Mountains area of the Brecon Beacons National Park in Mo ...
and
Tintern Abbey
Tintern Abbey ( cy, Abaty Tyndyrn ) was founded on 9 May 1131 by Walter de Clare, Lord of Chepstow. It is situated adjacent to the village of Tintern in Monmouthshire, on the Welsh bank of the River Wye, which at this location forms the bo ...
, 'Blue Pennant' sandstone in
Caerphilly Castle
Caerphilly Castle ( cy, Castell Caerffili) is a medieval fortification in Caerphilly in South Wales. The castle was constructed by Gilbert de Clare in the 13th century as part of his campaign to maintain control of Glamorgan, and saw extensi ...
and Sudbrook Sandstone at
Caldicot Castle
Caldicot Castle ( cy, Castell Cil-y-coed) is an extensive stone medieval castle in the town of Caldicot, Monmouthshire, in southeast Wales, built near the site of Harold Godwinson's former Saxon castle by the Norman earls of Hereford from ...
to name but a few. Triassic rocks provided the Radyr stone and also the Quarella stone which was worked at
Bridgend
Bridgend (; cy, Pen-y-bont ar Ogwr or just , meaning "the end of the bridge on the Ogmore") is a town in Bridgend County Borough in Wales, west of Cardiff and east of Swansea. The town is named after the Old Bridge, Bridgend, medieval bridge ...
.
Sutton Stone
Sutton stone is a geologic formation located only in South Wales. Sutton stone consists of white, conglomeratic limestones with pebbles of black chert (silica) and carboniferous limestones, laid down in early Jurassic times. It was named by geolog ...
from South Wales' Jurassic outcrop is a highly regarded limestone
freestone that has been used in construction throughout the Vale of Glamorgan, it was also shipped over the
Bristol Channel
The Bristol Channel ( cy, Môr Hafren, literal translation: "Severn Sea") is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England. It extends from the lower estuary of the River Seve ...
to
North Devon and
North Cornwall
North Cornwall ( kw, An Tiredh Uhel) is an area of Cornwall, England, United Kingdom. It is also the name of a former local government district, which was administered from Bodmin and Wadebridge . Other towns in the area are Launceston, Bude, P ...
which are both deficient in limestone.
The micaceous sandstones of Carmarthenshire's Tilestones Formation were formerly worked to provide roofing material, as were similar flaggy sandstones elsewhere, at least until the burgeoning of the North Wales slate industry in the nineteenth century.
Limestone
Limestone has been worked on a small scale for burning in limekilns over many centuries. In more recent times it has been quarried for use as aggregate, as a flux for the steel industry and as a feed for the chemical industry.
Coal
The working of coal in Wales' various coalfields began in earnest with the initiation of the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. Easily the most significant is the
South Wales Coalfield
The South Wales Coalfield ( cy, Maes glo De Cymru) extends across Pembrokeshire, Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent and Torfaen. It is rich in coal deposits, espec ...
though the contiguous
Flintshire
, settlement_type = County
, image_skyline =
, image_alt =
, image_caption =
, image_flag =
, image_shield = Arms of Flint ...
and
Denbighshire Coalfield
The Denbighshire Coalfield in the historic county of Denbighshire in north-east Wales is one of the smaller British coalfields. It extends from near Caergwrle in the north, southwards through Wrexham, Ruabon and Rhosllannerchrugog to Chirk in th ...
s were of importance to the economy of northeast Wales. A rather smaller coalfield was worked in
Pembrokeshire
Pembrokeshire ( ; cy, Sir Benfro ) is a Local government in Wales#Principal areas, county in the South West Wales, south-west of Wales. It is bordered by Carmarthenshire to the east, Ceredigion to the northeast, and the rest by sea. The count ...
and a tiny one in
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
.
Sand and gravel
Deposits of glacial and fluvial sands and gravels have been and continue to be worked in numerous areas, principally for the construction industry.
Geohazards
Wales is not a particularly seismically active country, nevertheless
earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
s of lesser magnitude occur from time to time. Ground stability is more of an issue due both to natural causes and, in former areas of coal and other mineral exploitation, due to mining, surface excavation and spoil deposition. Deep-mining of coal in particular has led to reactivation of pre-existing landslips, notably in the steeply-sided valleys of the South Wales Coalfield. Inappropriate placing of spoil material on such slopes has both overloaded them and disturbed drainage patterns with occasional catastrophic effect as in the
Aberfan Disaster
The Aberfan disaster was the catastrophic collapse of a colliery spoil tip on 21 October 1966. The tip had been created on a mountain slope above the Welsh village of Aberfan, near Merthyr Tydfil, and overlaid a natural spring. Heavy rain led ...
of 1966. An extensive programme of stabilisation works across the coalfield followed that event.
The contamination of land,
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
and watercourses is a risk in areas where mineral exploitation has taken place, notably in the
Central Wales Orefield
The Central Wales Orefield (also referred to as the Central Wales Mining District, Central Wales Mining Field and the Mid Wales Mining District) is an area of Mid Wales within which various metalliferous ores are present in the local rock strata a ...
and in former coal mining districts.
Geological conservation and interpretation
Numerous sites have been identified as important
earth science
Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres ...
localities within the
Geological Conservation Review
The Geological Conservation Review (GCR) is produced by the UK's Joint Nature Conservation Committee and is designed to identify those sites of national and international importance needed to show all the key scientific elements of the geological a ...
and afforded protection as geological
SSSI
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 of ...
s.
[Ellis et al 1996 ''An Introduction to the Geological Conservation Review'' GCR Series no 1, Joint Nature Conservation Committee, Peterborough ] See
here
Here is an adverb that means "in, on, or at this place". It may also refer to:
Software
* Here Technologies, a mapping company
* Here WeGo (formerly Here Maps), a mobile app and map website by Here Technologies, Here
Television
* Here TV (form ...
for complete list of both biological and geological SSSIs in Wales - some sites are protected in respect of both types of interest. In addition, two extensive areas are designated as
Geopark
A geopark is a protected area with internationally significant geology within which sustainable development is sought and which includes tourism, conservation, education and research concerning not just geology but other relevant sciences.
In 20 ...
s; the entire island of
Anglesey
Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...
as '
GeoMôn' in the north and
Fforest Fawr
Fforest Fawr is an extensive upland area in the county of Powys, Wales. Formerly known as the Great Forest of Brecknock in English, it was a royal hunting area for several centuries but is now used primarily for sheep grazing, forestry, water cat ...
within the
Brecon Beacons National Park
The Brecon Beacons National Park ( cy, Parc Cenedlaethol Bannau Brycheiniog) is one of three national parks in Wales, and is centred on the Brecon Beacons range of hills in southern Wales. It includes the Black Mountain (range), Black Mountain ...
in the south.
The Geoparks have a range of roles; conservation and promotion of the two areas' geological heritage are important ones. These objectives are partly achieved through educational and interpretive programmes. '
RIGS groups' are being established in different parts of Wales with the aim of supporting locations designated as
regionally important geodiversity sites and assisting in the implementation of
Local Geodiversity Action Plans ('LGAPs'). Local authorities and other agencies in the public sector continue to be involved in the acquisition of significant earth heritage sites, their conservation and interpretation. Charities such as Wales' wildlife trusts also have a similar role.
See also
*
Geology of the British Isles
*
Geology of England
The geology of England is mainly sedimentary. The youngest rocks are in the south east around London, progressing in age in a north westerly direction.
*
Geological groups of Great Britain
This is a sortable list of the groups into which the rock succession of Great Britain and surrounding seas is formally divided. Rock sequences are described by geologists by dividing them hierarchically thus: individual 'beds' of rock (or in the ...
*
Geological structure of Great Britain
The geological structure of Great Britain is complex, resulting as it does from a long and varied geological history spanning more than two billion years. This piece of the Earth's crust has experienced several episodes of mountain building or ' ...
*
Geology of Monmouthshire
: ''This article describes the geology of the Monmouthshire (historic), historic county of Monmouthshire. It includes the Monmouthshire, modern administrative county and the Principal areas of Wales, 'principal areas' of Torfaen, Newport, Wales, Ne ...
*
Geology of Carmarthenshire
*
List of geological faults of Wales
This is a list of the named geological faults affecting the rocks of Wales. See the main article on faults for a fuller treatment of fault types and nomenclature but in brief, the main types are normal faults, reverse faults, thrusts or thrust fa ...
*
List of geological folds in Great Britain
This is a list of the named geological folds affecting the rocks of Great Britain and the Isle of Man.
Terminology
See the main article on folds for a fuller treatment of fold types and nomenclature but in brief, an anticline is an arch-like fol ...
*
Geology of South Wales
*
Geology of Snowdonia National Park
The geology of Snowdonia National Park in North Wales is dominated by sedimentary and volcanic rocks from the Cambrian and Ordovician periods with intrusions of Ordovician and Silurian age. There are Silurian and Cenozoic sedimentary rocks on ...
*
Geology of Brecon Beacons National Park
*
Palaeontology in Wales
*
Geology of Great Britain
The geology of Great Britain is renowned for its diversity. As a result of its eventful geological history, Great Britain shows a rich variety of landscapes across the constituent countries of England, Wales and Scotland. Rocks of almost all geol ...
References
* Howells, M.F. 2007 ''British Regional Geology: Wales'' Keyworth, Nottingham: British Geological Survey 230pp
Snowdonia National Park AuthorityOfficial site of the Brecon Beacons National Park Authority*
*
* John L. Morton, ''King of Siluria — How Roderick Murchison Changed the Face of Geology'' (Brocken Spectre Publishing, 2004, )
*
*
*
Martin J. S. Rudwick, ''The Great Devonian Controversy: The Shaping of Scientific Knowledge among Gentlemanly Specialists'' (University of Chicago Press, 1985) — the rise of Murchison to power
*
James A. Secord
James Andrew Secord (born 18 March 1953) is an American-born historian. He is a professor of history and philosophy of science within the Department of History and Philosophy of Science at the University of Cambridge, and a fellow of Christ's Coll ...
, ''Controversy in Victorian Geology: The Cambrian-Silurian Dispute'' (Princeton University Press, 1986) — documents the battle between Murchison and
Adam Sedgwick
{{DEFAULTSORT:Geology Of Wales
*
Paleozoic geology
Mesozoic geology
Stratigraphy of the United Kingdom