- 340 million years ago
The sedimentary rock limestone of which Prestatyn Hillside is formed was being created from coral and shells of dead marine creatures deposited on the floor of a shallow tropical sea. That Graig Fawr in Meliden consists of the fossiled remains of a coral reef is evident from the fossils which can be found in abundance there today. - 300 million years agoMuch of the sea bed had risen to become a broad coastal swamp. Dead plants, including huge trees which were mostly related to ferns, accumulated to produce seams of coal amongst the clays, shales and sandstones that were also being deposited.
Prestatyn Hillside and Graig FawrThis was followed by a period of major earth movements, with the rocks being thrust up to form mountains. Cracks appeared in the limestone, into which mineral-rich solutions bubbled up from below the earth's surface, crystallising as they cooled to form veins of lead, zinc, silver and other minerals.
- 230 million years ago
By this time, material eroded from the new mountains was being deposited under semi-desert conditions to form the rock strata of the New Red sandstone.Since then there have been significant movements along fault lines. To the east, the rock was pushed up above that to the west. Gradually the soft overlying rocks were worn away, exposing the harder limestone beneath, which forms the north end of the Clwydian range of hills at Prestatyn today. The limestone continues beneath the Vale of Clwyd, but is hidden below layers of the more recently formed rocks.
- 1.6 million years ago to Today
In this period, a succession of glacial episodes known as the "Ige Age" has occurred, during which great glaciers have carved their way down the Vale of Clwyd. They have left behind today's broad flat valley with deposited layers of boulder clay (boulders and stones ground down to fine clay particles by the glacier - interestingly, much of Upper and Middle Prestatyn is built upon boulder clay). It is understood that in fact 4 distinct glacial periods have occurred in the area in the last 1.6m years. The most recent ended about 10,000 years ago, when a huge ice cap covering much of North America and Europe receded. If "Ice Age" is used to refer to long, generally cool intervals, during which glaciers advance and retreat then we are still in one today. Our modern climate represents a very short, warm period between glacial advances. In some of the interglacial periods the Prestatyn area has enjoyed a warm or even tropical climate and accommodated lions, elephants, hyaenas and hippopotamuses.The current Ice Age is believed to be the 4th Ice Age in the last billion years of the earth's history, each of which has consisted of many glacial advances and retreats. Previous Ice Ages are not believed to have had any major impact on the geological history of Prestatyn however, and probably occurred before our local mountains were formed in any case!
The Influence of the Area's Geology
Industry
The exposure of the limestone, resulting from the uplift of what is now the Clwydian Hills, made the rock easily accessible for exploitation by man. A number of quarries have been carved into the hills along this side of the Vale of Clwyd, most notably at Dyserth. Limestone is notable for the cracks along the horizontal bedding planes and vertical joints which make it relatively easy to extract. Much of the stone was burnt in limekilns to produce lime for the chemical industry or for use as a fertiliser. Limestone was also used in steel making. When placed in the furnaces it draws the impurities out of the molten iron ore to form slag, leaving pure iron which can then be combined with carbon to produce steel. Dyserth Quarry was the last to close, finally ceasing operation in 1981. The old quarries on Prestatyn Hillside itself have been rapidly taken over by nature since their last use in the 1950s. Limekilns and ore chutes can still be seen along Bishopswood Road.
Rich mineral intrusions occurred in the limestone around Graig Fawr. These veins ran predominantly from south west to north east and were mined extensively. The Talargoch mines were probably first dug by the Romans to extract silver or possibly lead. Silver continued to be mined during the Middle Ages and up to the mid-18th century when lead and zinc extraction became more profitable. Talargoch was one of the most important lead mines in the area, reaching its peak in the 1850s. At least ten shafts were sunk around Meliden, all connected underground by horizontal 'levels' following the ore veins. The main shaft was over 330m deep, but with the sea so near and the mine's low lying position, water seeping through the porous limestone became a major problem. The engine house at the Clive Shaft was built in the 1860s to house a massive steam engine for pumping water from the southern end of the mine workings. It is still visible today, adjacent to the Graig Park Hotel & Country Club. Unfortunately, the increasing costs of keeping the mine dry meant that the company was unable to compete against cheap imported ores, so in 1884 the mine closed.
The development of the mines and quarries was the main reason behind the growth of the villages of Meliden and Dyserth. The former Prestatyn-Dyserth railway line, along which a recreational footpath now runs, was originally built to serve the two industries. The opening of the railway in 1869 made transporting the ore far easier than the previous method of shipping it from the tiny ports of Rhuddlan or Prestatyn.
Recently, Denbighshire Countryside Service volunteers unearthed the remains of an old cottage called Pant-y-Fachwen on Prestatyn Hillside, located alongside the Offa's Dyke Path. Records indicate the cottage was the home of a mining family during the 19th century.
Bishopswood
Geology has played a part in the survival of Bishopswood as an important haven for wildlife. The steep slope of the hillside was of no value as agricultural land, so the trees remained uncleared. The mature oaks which dominate the woodland, together with numerous cherries and various other trees, provide food and shelter for a wide range of different small plants and animals.
Dyserth Waterfall
There are few surface streams on limestone because water drains rapidly down into the porous rock; though some fault lines have been eroded in the past to form steep narrow valleys. The exception is at Dyserth where a stream drops over the edge of a hard limestone bed, as a waterfall.
  
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Virtual Prestatyn Website Prestatyn Business Association, Tai Tywyn Business Centre, Sandy Lane, Prestatyn, LL19 7SF, UK. Tel. +44 (0)1745 887755 Fax +44 (0)1745 889704 E-mail mail@prestatyn.org.uk | |||
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