What happened next? And this is where Cork’s geological history comes to a very long halt. Unfortunately, we don’t know what Cork looked like during the hundreds of millions of years that followed. It is not that nothing happened after the limestones and the Variscan Orogeny, it is just that any post-limestone rocks and sediments were not deposited in this area or have since been eroded away. There is evidence from Cloyne that the area around the City sported a warm, tropical land area during the geological period called the Jurassic, the same period that covered a part of the reign of dinosaurs. But within the City we do not have any evidence of what the area looked like back then. The Ice Age/Quaternary landscape of “Cork City” From 350 million years to about 13,000 years ago the continents had separated and pretty much moved into the positions that we are familiar with today. A handful of millions of years ago, the Earth’s global temperature started changing between warm and cold periods of time. During the colder periods, widespread regions of ice built up around the poles, creating huge ice sheets that eventually reached down to Ireland.
During the Quaternary Period, expansive and thick ice sheets appeared over the area.
All of Ireland, including the area of Cork City, became covered by kilometres of thick ice layers. The ice sheets would have crept very slowly but destructively over large stretches of land, grinding mountains and forever changing the landscape they travelled over. As these massive ice sheets melted (until about 10,000 yrs ago), large rivers carried sediments away from them and laid these in the river valleys of the City. These strong rivers also carved river valleys into the Devonian and Carboniferous rock layers, such as the ones that are now the Glen River and River Bride. Huge volumes of these sediments finally ended up in the Lee Valley, creating deep layers of what we call Quaternary or glacial sediments.
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