Sea arch
Also called: Natural arch · Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 9, Ch 2 "Shaping of the Earth's Surface"
Meaning
A sea arch is a bridge of rock over the sea. It forms at a headland, a piece of land that sticks out into the sea. Waves attack the headland and carve sea caves into its sides. Over time two caves meet, or one cave cuts right through, and an opening forms under the rock. Waves keep widening the opening. In the end the roof of the arch collapses, and the outer part is left standing alone as a sea stack. So an arch is a short-lived stage in a coast's retreat.
Example
Neil Island (Shaheed Dweep) in the Andaman Islands has a well-known natural sea arch on its shore. Local people call it "Howrah Bridge".
Don't confuse with
- Sea stack: a stack is a pillar of rock standing alone in the sea after an arch's roof has fallen in. An arch is still a bridge joined to the land.
Related concepts
- Emergent coast
- Submergent coast
- Ria coast
- Longshore current
- Coastal erosion
- Sea cliff
- Wave-cut platform
- Sea cave
- Sea stack