Rectangular Limestone Shore Platform

 

Along a remote section of New Zealand coastline is the striking feature of regular, grid-like pattern of fractures cutting across the tilted rock layers. These are called joints – fractures in the rock where there has been little to no movement parallel to the fracture surface. It’s a remnant of an older shore platform composed of limestone, with layers dipping towards the sea. This remnant platform sits roughly 2 meters above the current high-tide level and, in many places, erosion has formed small, flat-topped stacks.

A prominent feature is the large cut-out section within the platform. This likely occurred because the rock here was less resistant than the surrounding areas. While the entire platform has joints (fractures), this particular spot may have had a denser network of fractures, or more intersecting ones, making it easier for waves to exploit and remove the rock. Alternatively, the tilted rock layers might contain beds of varying hardness, and this cutout could represent where a softer, more easily eroded layer was exposed at the coast.

For scale, observe the person standing beside one of the joints – it highlights just how large these rock formations are.