Sea caves are transformed into sea stacks through a continuous process of erosion, ultimately leading to the collapse of cave roofs and the isolation of resistant rock formations.
Here's a breakdown of the process:
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Initial Formation of Sea Caves: Waves relentlessly attack weaknesses in coastal rock, such as joints or faults. This erosive power gradually carves out cavities along the shoreline, forming sea caves.
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Cave Expansion and Arch Formation: Over time, wave action and weathering processes continue to erode the sea cave. The cavity becomes larger and deeper. If two caves erode towards each other or a single cave extends far enough into a headland, it can eventually create a natural arch. This is a sea arch – essentially a bridge of rock over the sea.
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Arch Collapse: The sea arch is inherently unstable. The constant pounding of waves, coupled with weathering from wind and rain, weakens the arch's roof. Eventually, the roof collapses due to gravity and the relentless erosion.
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Stack Isolation: When the arch collapses, the remaining isolated pillars of rock that once supported the arch are known as sea stacks. These stacks are resistant sections of the headland that withstand the wave action for a period.
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Further Erosion of Stacks: The sea stacks are not permanent features. The same erosional forces that created them continue to wear them down. Over time, stacks will become smaller and eventually collapse, disappearing entirely beneath the waves or leaving behind small rocky platforms.
In essence, sea caves evolve into sea arches, and the collapse of these arches results in the formation of sea stacks, which are then further eroded.
