Geology

Tidal limestone platform

Kaikoura Peninsula is made of limestone and siltstone laid down beneath the sea about 60 million years ago; it has been exposed to the elements for a mere 180,000 years. Once an island, it is now linked to the mainland by debris eroded from the Kaikoura mountains, These mountains are rising faster than any other mountains in New Zealand (10 mm per year) but erosion keeps their height fairly constant.

Periods of rapid uplift have formed the steep-sided promontories, ideal for pa sites, and have twisted the neatly layered limestone into unusual shapes. The relatively young rocks have been worn into many interesting forms by the pounding sea. In less active periods, the sea has cut large tidal platforms in the softer sandstone.

Offshore is a very deep underwater canyon system called the Hikurangi Trench. It comes unusually close to shore at Kaikoura, where it is known as the Kaikoura Canyon. The canyon floor collects sediments that will form tomorrow’s rocks and may appear in millions of years’ time as new mountains.