The town of is situated where the The Geology of Welshpool were only worked for the duration of the project. With Welsh uplands meet the wide floodplain of The bedrock of the town was deposited between 460 the arrival of the canals and railways stone could be the . The town is reputed to and 420 million years ago, during the Ordovician and imported from a greater distance and a massive have been the Silurian periods, though most expansion in building occurred. Stone remained the th site of churches of the town actually rests on principal building material until the end of the 19 boulder clay and glaciofluvial century when more modern methods of brick founded in the 6th deposits from the last Ice Age. production were introduced. Many buildings were then century by St. The sediments from which the built from brick. During the 1960's the development of Cenfelyn and his local bedrock was formed pre-cast concrete began to compete with natural brother Llywelyn. were deposited in a large materials and, more recently, imported building In the 13th century subsiding marine trough, an materials, for example from Australia and China, are Welshpool was ancient sea which geologists competing with those quarried and manufactured at granted a borough call the Welsh Basin, when Silurian Shale home. charter and the lay south of the town which then Equator near the edge of a small continent, Avalonia. Building stones to be seen around Welshpool developed formed These sediments accumulated on the edge of the Igneous Rocks are formed from molten rock Welsh Basin and were dislodged by earthquakes or (magma). If the magma cooled slowly the individual the core of what is High Street, Welshpool. fierce storms, avalanching down the basin slope. crystals formed are large and can be seen with the Welshpool today. Repeated flows of this kind led to the distinct layering naked eye, but if cooling occurred quickly a much finer Like other towns in the area Welshpool suffered at of mudstones and sandstones. At times the sea-level grained rock results. the hands of Owain Glyndwr during his rebellion was low enough for Welshpool to become a beach. Examples to be found on the walk are: against King Henry IV in 1400. Today the national Under the influence of plate tectonics the Iapetus walking trail, Glyndwr's Way, runs through the Ocean to the north of Avalonia gradually closed as the Granite is formed slowly at town. oceanic crust was subducted (drawn down into the depth, resulting in large The woollen earth) beneath the continental crust at the sides. In crystals. Often used for industry brought this way Avalonia moved northwards. The subducting building in the past, it is now prosperity to oceanic crust caused volcanism as it passed deep into usually confined to street Welshpool during the Earth, leading to the igneous rocks of Standard kerbing and setts, cladding on Quarry, the Breidden Hills and Montgomery Castle. At commercial buildings, and medieval times the end of the Silurian period Avalonia collided with monumental masonry. and there are Laurentia, uniting the north and south of the British th still several 15 Isles. The resulting orogeny (mountain building) 410 to Dolerite is medium-grained, and 16th century 380 million years ago squeezed and uplifted the tough and hard. It occurs in timber buildings district, causing folding, faulting, and metamorphism of dykes and sills intruded into Powysland Museum in the town. the rocks. fissures in older rocks. The Transport links to the town increased with the “Bluestones” of Stonehenge opening of the Montgomeryshire canal in 1796 and Building Stones are dolerite. the Cambrian railway in 1862. This and the growth Local stone was first used to build places of worship, of the flannel industry improved prosperity. The fine whilst dwellings were usually constructed of wood. It Georgian houses are testament to the wealth was probably the Romans who first used sophisticated quarrying methods to obtain stone for building. In the Trachyte is fine-grained rock produced. following centuries stone was used extensively for the which is usually formed Agriculture and tourism now form the major construction of high-status buildings like castles and extrusively as lava, but industries around Welshpool, which also has the churches, whilst homes continued to be constructed of sometimes intrusively as a most modern livestock market in the UK and the wood. dyke or sill. It comes from largest one-day sheep sale in Europe. As prosperity increased houses began to be built of Standard Quarry and is much stone, at first obtained from local quarries which often used in the town.

Sedimentary Rocks are formed from the This leaflet was prepared by members of Mid Wales accumulation of material derived from weathered Geology Club, with guidance from Dr John Davies, fragments of other rocks. These sediments accumulate formerly regional geologist with the Countryside under water or on dry land, often display a layered appearance, and may contain fossils. Council for Wales. Mid Wales Geology is an amateur club with an interest in the earth sciences. Sandstone accumulates either Beginners are always welcome: in water or as a wind blown contact Bill Bagley 01686 413967 deposit in arid continental or look at the website. areas. Desert sandstones tend to be red, with individual Evening meetings are held monthly, usually on the sand grains often spherical third Wednesday, at Plas Dolerw, Milford Road and polished. Newtown. Monthly guided field trips are held on Sundays. Limestone is mainly calcite Photography by Bill Bagley, Richard Becker, and and generally forms in warm shallow seas from members of Mid Wales Geology Club. precipitation of calcium carbonate from the sea water, Mae'r fersiwn o'r daflen hon ar gael yn y or from the accumulation of Gymraeg. shells and skeletons of Hefyd ar gael i'w llwytho i lawr fel ffeil PDF. calcareous marine organisms.

Metamorphic Rocks are igneous or sedimentary This leaflet is also available to download from rocks which have been altered by a combination of the club website in English and Welsh. heat and pressure.

Slate is a fine-grained metamorphic rock formed from mudstones subjected to relatively low temperatures and pressures. It splits easily and is ideal for roofing. The mudstones from around Welshpool are not sufficiently metamorphosed to form slate, but are in the form of shale.

Bricks are man-made from clay or crushed shale. The colour produced depends on the minerals present and the as part of conditions during the firing. Welshpool's Geological Heritage Project You will see different sized and coloured bricks on the walk. Printed by Aztec Print Llanidloes 1. The walk commences at the Powysland 4A. and 4B. As you walk along the pavements Museum. Founded in 1874 by the Powysland Club, take note of the flagstones the museum was re-housed on it's present site in and kerbing. The flagstones 1990. The building is a former two-storey warehouse are sandstone, probably for the Montgomeryshire canal, built of brick from imported from India. Look the local brickworks. closely, you will see ripple marks formed by wave or The window surrounds are current movement over Cefn sandstone deposited in the soft sediments. The a deltaic environment during kerbstones are granite, the Carboniferous period probably from China. about 325 million years ago, 5. Royal Oak Hotel. This is a mid 18th century and once quarried near building built from brick. The bricks are irregular in Wrexham. size, suggesting that they were handmade using clay from local brick pits. Bricks were being manufactured 2. 18 Severn St. This house was re-modelled in th 1863 in the Gothic Revival fashion by the solicitor in Welshpool from the 16 Abraham Howell. It has a porch of Cefn Sandstone century, and on a large scale and uses three different colours of bricks in a from 1620 by the Herbert decorative pattern. Brick is, in effect, a man-made family at Montgomery metamorphic rock manufactured from clay. The Castle, but this brickworks different colours arise from a combination of the was destroyed during the minerals present in the clay civil war 25 years later. The and the temperature at which Doric coloumns of the porch the brick is fired. Red is due are unusual in that one is to the presence of iron oxide Cefn sandstone while the other is Grinshill. while yellow comes from the presence of lime. Firing at 6. St. Mary's Church. Founded in 6th century by St. very high temperature with Cynfelyn, the present church dates from the 13th low oxygen results in a blue century but with much recent addition and brick. rebuilding. The south steps up from the street are Cefn sandstone. The wall 3. 24 Severn Street. This building is now the buttresses and the War County Court but was originally built c1820 by the Memorial are Permo-Triassic lawyer Richard Griffiths-Parry. The portico porch has sandstone probably from coupled doric columns of Shrewsbury. The new church Cefn sandstone, although entrance was built in 1871 the column bases have with an arch and steps using been replaced recently with white Cefn and red Grinshill Carboniferous age 'Pennant' sandstones. sandstone from the Forest Later replacements of the top steps are 'Pennant' of Dean. sandstone. To the side of the porch is coursed rubble walling, with some stones reused from the Cistercian Abbey of Strata Marcella, which was dissolved in 1536.

Stones for rubble walling of 12. Methodist Church. Built in 1874 on land the church will have been purchased from the Powis estate. It has window collected from as near to surrounds of Jurassic age Box Ground stone, a type of the building site as Bath Stone which shows long “snail-trails” and possible. The sundial in the weathered-out shell layers. If you look closely you will churchyard is red Triassic see that it is composed of sandstone, it's base coming small spherical grains known from part of the 1608 churchyard cross. A large as ooliths, formed by the rough-cut glacial boulder next to the sundial is said precipitation and accretion of to have formed part of the Abbot's throne at Strata carbonate around small Marcella. grains and shell fragments rolled along the sea floor. 7. Town Hall. Built in 1874 on the site of an earlier Many fossils are to be found 19th century building, it is of French neo-classical in this stone. design and built of yellow Grinshill sandstone. Much of the sandstone is visibly crumbling due to weathering. 9. Bear Passage. The wall half way down Bear Grinshill sandstone comes from , it is Passage is a good example of rubble work. Various Triassic in age (about 240 million years ago), and 13. Park Lane. On the wall to the right you will find a stones have been used in its construction. A. Powis represents wind-blown dune sediments deposited good example of the Conglomerate. This Castle Conglomerate. B. Old Red Sandstone. C. when Britain lay 20o north of the equator. It comes in red rock is composed of sand, pebbles, and a few Trachyte from Standard Quarry. D. A boulder from the different colours, red due to boulders. It originated as a beach deposit on the glacial boulder clay. E. local Silurian mudstone. F. Old the grains having a coating of shores of a sea that covered most of Wales during the bricks. iron oxide whilst white is the Silurian period, about 440 result of the oxide removal by million years ago. The red 10. 1-3 Park Terrace. A terrace of three houses fluids from an igneous colour, due to the presence identically planned and built in the late19th century of intrusion during the of iron oxides, developed brick but with terracotta Palaeocene, 60 million years much later during the lintels and mouldings. ago. Yellow results from Permian period, 260 million Unglazed terracotta became partial removal of the iron years ago, when Wales had fashionable in mid 19th oxide. a hot desert type of climate. century, the colour varied with the clay used. Ruabon 8. 41 High Street. This shop front is granite, possibly clay from near Wrexham imported from Portugal. The step is Carrara marble producing a bright red. from Tuscany in Italy. Used since the time of ancient 14. New Street, The Cockpit. This 18th century Rome, it is the same Jurassic marble (140 million hexagonal building is one of only three known brick- 11. 41/42 Mount Street. These houses were years ago) from which Michaelangelo's David was built cock-fighting pits in remodelled in the 19th century using trachyte from carved. Metamorphism has Wales. The small irregular Standard Quarry on the caused recrystallisation of the bricks are hand-made, Western edge of Welshpool original limestone grains. probably at one of the local, town. Look closely at this White marble comes from small-scale brickpits. The stone, you will see that the pure white limestone; the wall to the right is igneous grains are much smaller than swirls and veins of coloured stone from nearby Criggion in granite, because this rock varieties are due to impurities, quarry, a dolerite with rotting has cooled more quickly. particularly iron oxide. feldspar crystals.