The Cliffs of Moher located on the rugged west coast of Ireland have been carved out of the landscape over the course of millennia by the raging Atlantic ocean grinding away at the sandstone , siltstone and shale that dominate this part of the country . The siltstone has a much higher clay content than sandstone and so is less resistant to erosion , this explains the why parts of the cliff stick out from the cliff face as they erode quicker than the sandstone parts of  the cliffs which are set back further .
Cliffs of moher Geology