The White Rocks are tall cliffs made of chalk to the east of Portrush. They were formed when the sea was much shallower, and dinosaurs roamed the Earth. The chalk is composed of the skeletons of tiny single-celled organisms which accumulated on the seabed and were later compressed over time. Chalk also formed in other areas in North-East Ireland, but some of the other areas of soft rock have been reduced or removed through coastal erosion. The chalk bed at the White Rocks remains intact as it was capped by a layer of hard basalt rock which takes much longer to erode.
Coastal erosion is when the rock is ‘eaten away’ by the sea or by other rocks. There are four different types of coastal erosion which create the interesting shapes of the rocks we can see today at the White Rocks:
- Abrasion (sometimes called corrasion) is when the sea throws pebbles and sand against the rock and acts like a wrecking ball or sandpaper in grating away the rock face.
- Hydraulic Action is when the waves push water and air into cracks in the rock and causes the rock to shatter due to the force of the air being compressed and expanded.
- Solution (sometimes called corrosion) is the sea dissolving soluble materials like calcium carbonate from the rocks such as chalk and limestone.
- Attrition is when the rocks which have already been broken off from the main rock face knock against each other and are slowly worn into smaller boulders and pebbles.
Erosion makes different shapes and coastal rock forms such as caves, which can turn into arches and finally stacks and stumps as the sea erodes further into the rock. The White Rocks have examples of these features.
The chalk in the White Rocks is full of fossils, many of which are the tubular-shaped belemnites. It is also contains considerable quantities of flint, which was used by Stone Age communities to make weapons and tools. It can also be used to make fires and is considered a survival skill even today. Archaeologists have discovered several Stone Age settlements along the coast, and it is believed that the abundant supply of flint to make tools, the fish for food and the fresh drinking water from nearby streams were what attracted these people to live here almost 9,000 years ago.
Dr AEP Collins concluded that the importance of the White Rocks sandhill site which he excavated in 1971 lay in the fact of the number of structures and objects which typologically could be assigned to periods ranging from the Neolithic to the Medieval on a single old land surface. C-14 carbon dating demonstrated this convincingly. The number of worked flints found at the site may indicate that it was an industrial site ie a “Flint Factory”; however, this could not be conclusively proven.
In more recent centuries, chalk was burned in kilns to make quicklime which helped to enrich soils for farming and was also used extensively in making Lime Mortar for building. Lime is still used by farmers to enrich their soil and make it more workable, which is why you can see the fields covered in a white substance between Winter and Spring as farmers prepare their fields for the planting season in the Spring.