Sea arches are formed through a fascinating process of erosion by waves and water.
The Erosional Process: From Cave to Arch
The formation of a sea arch begins with the relentless pounding of ocean waves against a headland, a stretch of land projecting out into the sea. Over time, this constant wave action erodes weaker areas of the rock, creating cracks and eventually sea caves.
As the waves pound into these new sea caves, the water hits the back wall of the cave and refracts. The force of the water bouncing off the back wall then begins to erode the cave's headland. This continued erosion, often aided by factors like salt spray and freeze-thaw cycles, gradually weakens the rock, widening the cave. Eventually, the process creates a passage through the headland, forming a magnificent sea arch.
Key Factors in Sea Arch Formation:
- Wave Action: The primary force behind erosion. The consistent pounding of waves is crucial.
- Rock Type: Softer rocks erode faster than harder ones, influencing the speed of arch formation.
- Joint Patterns: Pre-existing cracks and fractures in the rock provide pathways for water penetration and erosion.
- Tidal Action: The rise and fall of tides expose different parts of the headland to erosion.
Example: Imagine a coastal cliff face with a pre-existing crack. Waves continually batter this crack, widening it into a cave. As the cave expands, the constant pressure of the waves erodes the rock, eventually creating a hole all the way through – a sea arch.
