When a sea arch collapses what remains?

When a sea arch collapses, the remaining structures are typically sea stacks or isolated pillars of rock that were once part of the arch's support. Additionally, the surrounding coastal landscape may feature cliffs, wave-cut platforms, and other erosion-related formations. The collapse is caused by continued wave action and erosion, which weakens the arch over time. Ultimately, the remnants serve as a testament to the dynamic processes of coastal erosion and geological change.