Where you have strident blocks of cliffs or rocks on the coast they can appear both monotonous and overwhelming unless you break them up somehow. An excellent way to do this is to watch for those dynamic splashes of boisterous surf hitting the rocks and use them to break up the mass of solid rock. I often exaggerate these to a degree so that they can be more effective. This is not cheating as I often come across the most enormous and sometimes terrifying waves smashing up against the shore.
The illustration shows wild waves crashing against a long rib of rock on the west coast of Pembrokeshire. effectively breaking it up so that it appears as two different blocks of rock. Although it is an original sketch carried out on the spot with a water-soluble graphite pencil, the technique applies equally to a painting in any medium. I had just scrambled down the rocks on the left after exploring the bay on the far side, without getting too wet. The gulls added further dynamism and life to the composition.
Whether you enjoy working outdoors on location as I do, or prefer to stay indoors, it is worth breaking up features that might otherwise dominate a scene, as in this case. You don't need to completely obliterate the central part of the feature, but it really is worth doing a small thumbnail sketch before you carry out a full painting. That will help you decide how far to go with any changes to the scene.