Geology
The chalk was formed in the Late Cretaceous period, between 65 and 100 million years ago, when the area was under the sea. During the Cenozoic Era the chalk was uplifted (see Cenozoic Era). When the last Ice Age ended, sea levels rose and the English Channel formed, cutting into the chalk to form the dramatic cliffs along the Sussex coast.
Wave action contributes towards the erosion of cliffs around Beachy Head, which experience frequent small rock falls. Since chalk forms in layers separated by contiguous bands of flints, the physical structure affects how the cliffs erode. Wave action undermines the lower cliffs, causing frequent slab failures - slabs from layers of chalk break off, undermining the upper parts of the cliffs, which eventually collapse. In contrast to small rock falls, mass movements are less common. A mass movement happened in 2001 when, after a winter of heavy rain, the water had begun to seep into the cracks which had frozen and caused the cracks to widen. This then made the cliff edge erode and collapse into the sea.
Read more about this topic: Beachy Head