6.11.1. Cliffs, Terraces, Caves and Stacks

Wave-cut cliffs and terraces are two forms usually found where erosion is the dominant shore process. Almost all sea cliffs are steep and may range from a few m to 30 m or even more. At the foot of such cliffs there may be a flat or gently sloping platform covered by rock debris derived from the sea cliff behind. Such platforms occurring at elevations above the average height of waves is called a wave-cut terrace.

Wave-cut cliffs are steep heights on the coastline formed by the erosive power of waves crashing against the rock. The force of the waves can create a flat area or platform at the base of these cliffs, known as a wave-cut terrace. These terraces are found at levels above the typical high tide and represent where the coastline has retreated over time due to erosion.

Imagine a strong wind blowing against a tent. Over time, the continual pressure from the wind causes some parts of the tent to wear down and bend out—it becomes more flat in places nearest the ground. Similarly, waves continually hitting against a cliff cause parts of it to wear away, eventually forming these terraces at the cliff's base.

The lashing of waves against the base of the cliff and the rock debris that gets smashed against the cliff along with lashing waves create hollows and these hollows get widened and deepened to form sea caves. The roofs of caves collapse and the sea cliffs recede further inland.

As waves strike the base of a cliff, they begin to excavate hollows or indentations. Over time, these hollows deepen and widen, leading to the formation of sea caves. Eventually, the material supporting the roof of these caves can collapse, causing the cliff to retreat further back from the shoreline.

Think of a sculptor chiseling away at a block of stone. With each strike, the sculptor removes material, creating a hollow shape. Similarly, the continuous striking of waves against the rock chisels away the cliff, eventually leaving a cave behind.

Retreat of the cliff may leave some remnants of rock standing isolated as small islands just off the shore. Such resistant masses of rock, originally parts of a cliff or hill are called sea stacks.

As erosion continues to wear away the cliffs, some harder rock formations that are more resistant to erosion can remain as isolated pillars in the sea, known as sea stacks. These stacks become visible above the water after the surrounding softer rock has eroded away.

Imagine a layer cake where you keep removing the soft sponge layer but the hard topping remains intact. This hard part, like the cake topper, remains while the sides gradually disappear, resembling how sea stacks stand as remnants of the cliff after erosion.

Like all other features, sea stacks are also temporary and eventually coastal hills and cliffs will disappear because of wave erosion giving rise to narrow coastal plains, and with onrush of deposits from over the land behind may get covered up by alluvium or may get covered up by shingle or sand to form a wide beach.

The coastal landscape is dynamic and constantly changing due to the persistent action of waves. Over time, as sea stacks and cliffs erode, they are washed away, leading to a transformation where wide sandy beaches may develop. This process highlights the changeable nature of coastal environments.

Consider the process of baking cookies. When first taken out of the oven, they appear whole and intact; however, as they cool and sit out, they may crumble away. In a similar manner, as coastal cliffs wear away, they reshape into new landforms, creating beautiful beaches.

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