Geological History
The geology and landforms around Prestatyn are the result of a wide variety of processes and conditions, many of which occurred thousands of miles away and millions of years ago. Because of the gradual movement of sections of the earth's surface (known as continental drift) this area now lies much further north than it did when it was formed.
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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 ago
Much 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.
This 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!
