What kind of rocks form cliffs

Steep cliffs are formed where the land consists of hard, more resistant, rocks, their height obviously being determined by the difference between the sea level and the level of the land. Hard rocks erode and weather slowly, and the less fractured the rock is, the better it will resist breaking down.

Igneous rocks such as granite and basalt form rugged vertical cliffs such as those along the Cornish Atlantic coast at Lands End. Granite is a very strong rock and such cliffs can withstand constant pounding by Atlantic storm waves. Softer rocks, such as clay, shale and some sandstones erode more easily and can create more gently sloping cliffs, although this is not always the case. Sedimentary rocks that have been laid down in distinct strata may dip towards the sea or away from it.

This has the effect of either presenting a smooth surface towards the sea or a rough broken surface. A smooth angled surface will better resist waves than a rough broken surface, so the same rock can form different types of cliff according to how the rock surfaces face the sea. Hard rocks are more resistant than soft ones, and will form steep cliff faces.

This nearly vertical cliff on the north Cornish coast has been formed from basalt, a very hard igneous rock. Soft cliffs often have a beach at the base, with an intertidal veneer of sand and gravel. Several processes contribute to erosion of shore platforms. Attack by waves armoured with rock fragments is an effective erosion mechanism, which polishes the platform surface.

Fine abrasive material is washed away by waves and currents. However, platform surfaces usually present also many irregularities, with gullies, ponds and potholes scoured in faults, joints and in excavations of less resistant rock around hard outcrops.

Chemical and physical weathering plays an important role, through the effects of alternate wetting and drying, salt crystallization and frost. Marine organisms see Rocky shore habitat accelerate platform erosion by grazing activity surface scraping and by boring of holes by bivalves.

Algae e. Log in. Page Discussion. Read View source View history. Jump to: navigation , search. Types of sea cliff after Carter [2].

Copyright: J. Pat Doody. Cliffs and Rock Coasts. Flemming, B. Coastal Environments. These sediments were buried deeper by more layers and eventually turned to rock. It took million years for those rocks to get to where they are now. During that long bumpy journey, the rocks were fractured by colliding with another tectonic plate. This collision led to the formation of deep vertical fractures; it is these fractures that give the cliffs their vertical appearance now because when the rocks are eroded they fall along these vertical layers of weakness.

So, when you look at the magnificent Cliffs of Moher you are watching a million-year-old story of rivers and mud and mountains and continents colliding and the tracks of mysterious creatures that lived and died and are preserved in those layers of rock. Coastal erosion is likely to accelerate due to global warming. The Cliffs are under constant attack from the enormous waves that batter them every day and this leads to erosion which results in fairly regular rockfalls, so please stick to the marked path and let the Cliffs be what they are; an active, dynamic landscape that provides a home to thousands of birds and a world-class visitor attraction that tells the amazing story of our geological journey and a vital part of the Burren and Cliffs of Moher UNESCO Global Geopark.

Looking out from the top of the cliffs you will see many coastal landforms: Sea Stacks, Sea Stumps and caves that have been formed as a result of erosion. These features will be regularly populated by up to 20 different species of birds. You cannot miss the great sea stack — Branaunmore, standing 67 metres high.