Arched rock, Mercury Island

Arched rock, Mercury Island

This hand-coloured engraving was made by Sydney Parkinson, the artist on board Captain James Cook’s Endeavour in 1769. It shows a fortified pā on top of an arched rock at Mercury Bay, on the Coromandel’s east coast. Arches form when waves pound headlands from both sides. Over time, the waves follow lines of weakness in the rock, and carve out caves on either side of the headland. When the caves meet, a natural arch is produced. This structure has since collapsed.