Coastal cliffs and shorelines above existing sea level are explained by the process of isostasy (the intermittent rise of land after glaciation). Thick glaciers depress the land into deeper layers in the Earth and as they melt the unloaded land mass rises, stabilising periodically for long enough to allow the sea to cut coastal features.
At Ballyquintin Point, there is evidence for two raised shorelines: the first at the 10m contour; the other at, or just above, existing sea level. The first is a low cliff cut into boulder clay fronted by a terrace of red marine clay that gradually descends to present sea level. The second is a platform cut into the near vertical Silurian bedrock that underlies this entire landscape. Such wave-cut platforms at present sea level would normally be considered modern features but this platform extends behind high water mark where a pebble and cobble deposit formed from the Silurian bedrock rests on it and appears to extend landward to the foot of the low cliff in places. This deposit is at least 2m thick and its surface is crossed by ridges around 1m high that run parallel with the cliff. There are some suggestions that the age of the cliff and the red clay are late glacial, but the wave-cut platform at modern sea level has no published account.
The site has great potential for research into isostatic uplift in the area, for fundamental work on the pebble and cobble deposit and for the relative dating of events, including the red marine clay.