Water causes a sea arch through the erosive power of waves, specifically when waves refract around a headland protruding into the ocean.
Here's a breakdown of the process:
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Headland Formation: A headland is a piece of land that projects out into the sea. These landforms are often made of resistant rock.
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Wave Refraction: As waves approach a headland, they bend or refract around it. This bending concentrates wave energy on the sides of the headland.
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Erosion Concentrated: The focused wave energy erodes the rock along the sides of the headland, particularly if there are pre-existing weaknesses like faults, joints, or fractures.
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Cave Formation: Over time, the concentrated erosion can create caves on either side of the headland.
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Arch Formation: If the caves erode far enough, they can eventually meet in the middle, forming an arch. The arch is essentially a natural bridge of rock.
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Arch Collapse: Eventually, weathering and continued erosion weaken the arch, leading to its collapse. The remaining isolated rock pillars are called sea stacks.
In summary, the combination of wave refraction around a headland, concentrated erosion on its sides, and the presence of weaknesses in the rock leads to the formation of a sea arch. The constant pounding and chemical action of seawater gradually wears away the rock, sculpting this dramatic coastal feature.
