Geology of Mourne AONB
Where did the Mournes come from?
| The Mournes are comparatively 'young' mountains and are composed of hard, acidic granite. They developed when a vast block of ancient shale subsided deep into the earth's crust. As it did so, molton granite welled up in stages around the sides of the descending block and filled the 'roof cavity' left in its place. Their formation complete, the granite Mournes were still concealed beneath an overlying mantle of the original shale which has almost all since gone; worn away by millions of years of rain, ice and running water. |
Since their formation some 50 million years ago, periodic climate changes have altered the mountains' appearance, notably the erosion and deposition which occurred during a series of Ice Ages. Ten thousand years ago the last ice sheets retreated, depositing in their wake vast quantities of sand and gravel. This covered the coastal plain to a depth of many feet, and included countless granite boulders swept down from the mountains. At higher levels the shape of many valleys were modified by the erosive power of advancing ice. The striking U-shaped profile of the Hare's Gap is one well know example of a pass shaped by the passage of ice.
