The rocky outcrops, known as tors, and the accumulations of broken rock that are such distinctive features of Carningli’s high, dramatic ridge are evidence of the influence of ice. During the peak of the last ice age, 25,000-20,000 years ago, when many other parts of Wales were covered by ice, these highest parts of north Pembrokeshire were likely to have been ice-free. However, weathering processes, which involve the slow breakdown of solid rock by a range of physical and chemical processes, would have continued in the cold conditions. One key process that would have been common is freeze-thaw activity, which happens when water freezes and thaws repeatedly in cracks in the rock. As water freezes it expands. Over time, repeated freeze-thaw cycles mean that the cracks are continually expanding and then contracting as the ice turns to water once more. This weakens the rock, contributing to its slow disintegration and causing entire sections to break off in a process known as frost shattering. This activity commonly occurs in frozen ground in and near ice-covered areas and can produce outcrops of partially weathered rock, the tors, alongside the angular rock fragments found on the slopes.
