The Boulder Bank

The Boulder Bank is a very unusual naturally formed land form in Nelson, New Zealand.  It is a 13 kilometre long stretch of rocky  substrate which begins at the Mackay Bluff and ends at the Cut of the Nelson Hurbour. Haulashore Island was once a part of the Boulder Bank, but since the Cut was made it is an island, and no longer connected to the Boulder Bank. The Boulder Bank separates Tasman Bay and the Nelson Haven.  The Boulder Bank is composed of granodiorite. The source of this rock is Mackay Bluff. It is still debated what process or processes have resulted in this odd structure. Longshore drift? Tasman Bay does not receive enough wave action to move the large boulders in a south west direction. Studies have been conducted since 1892 to determine speed of boulder movement. Rates of the top course gravel movement have been estimated at 7.5 metres a year. however this is the most accepted hypothesis for creation.