How were the Apostles formed?

How were the Apostles formed?

The rock stacks are the temporary remnants of a retreating limestone coastline, under constant attack by the sea.  Cliff faces are being eroded at the rate of about 20mm each year.

Cliff face erosion: Wave action erodes the cliff face, leaving harder rock as a headland.

 

 

 

Caves and arches: Waves eat away the rock at sea level, forming caves on each side of the headland.  The caves eventually meet up, forming an arch.

 

 

 

Stacks form: Over time the arch collapses into the sea, leaving a rock ‘stack’.

 

 

 

Further undercutting: Further undercutting by waves, and opening up of vertical cracks in the rock by rain and saltwater, gradually reduce the stack to a low platform or reef.  This occurred spectacularly in 2005, making world-wide news.

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