Why do cliffs erode into arches?
Show answer & explanation
Answer: Waves undercut rock layers
Waves undercut rock layers ✓ — Correct! Waves constantly pound coastal cliffs, exploiting cracks and softer rock layers. They hollow out caves at the waterline on both sides of a headland. When caves meet through the rock, an arch forms! Eventually the arch top collapses, leaving a sea stack. It's erosion sculpting rock over thousands of years!
Animals dig through rock — Wrong. Animals can burrow in soil but don't create rock arches. Wave erosion is the primary force carving coastal arch formations.
Acid rain dissolves arches — Wrong. Acid rain can dissolve limestone, but dramatic coastal arches are carved by mechanical wave erosion, not chemical dissolution.
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