A rough map of the area during the Late Devonian Period that is today County Cork.
The eroding rock material from the Caledonian mountains was transported to the area of“Cork City”through rivers in the form of sand, silt and mud. This loose rock material is what we call ‘sediments’ and it is the origin of the sandstone, siltstone and mudstone layers we find in the City today. The mountain-building processes came to an end, however the crust was still moving. During the Devonian Period other areas of the planet’s surface, or more correctly, its crust, were pushed downwards and sideways due to the immense pressures from the colliding landmasses. In Cork, a large area of the crust subsided and became more low-lying relative to the surrounding land. A low-lying area such as this is called a sedimentary basin. We call this subsided region the Munster Basin. The Devonian floodplains of “Cork City” The mountain-derived sediments started filling the Munster Basin and by 380 million years ago the entire region was made of widespread, flat, dry floodplains. Due to the movements of landmasses and continents, Cork was closer to the equator back then and thus had a much warmer climate than today. Despite the higher temperatures, it would not have been an ideal holiday destination, as the illustration above shows. Seasons would have been more dramatic than in today’s Cork, with long dry and wet periods. During wet periods, rainfall would turn calm rivers into large floods, while during dry periods the ground would form cracks like we see in deserts today. We refer to this environment as ‘semi-arid’ as it would mostly have been dry but still with some occasional rainfall. All the sediments making up this semi-arid area would have come from the huge Caledonian mountains to the north of the area. We talked about these mountains earlier when discussing the geological history of Cork. As the mountains eroded, all the material cascading down from them would have been carried by rivers to the lower areas of the Munster Basin, which is today Cork. When all these sediments were buried and subjected to heat and pressure over millions of years, they were compacted into the Old Red Sandstone that we find today all across the county.
But like any other point in Earth’s history, landscapes are never static.
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