During the Carboniferous period (325 million years ago), Ilkley Moor was part of a sea level swampy area fed by meandering river channels coming from the north. The layers in the eroded bank faces of stream gullies in the area represent sea levels with various tides depositing different sorts of sediment. Over a long period of time the sediments were cemented and compacted into hard rock layers. Geological forces lifted and tilted the strata a little towards the south-east, producing many small fractures, or faults.