Boulder Bank

The Boulder Bank is an unusual natural landform off the coast of the New Zealand city of Nelson . It is a 13 km long, narrow gravel bank that stretches from Mackay Bluff in the east today to the "Cut", the artificially created harbor entrance. Haulashore Island , southwest of the cut, was also part of the Boulder Bank until the breakthrough. Seen from the land, the Boulder Bank looks like an artificially raised breakwater. It separates Nelson Harbor from Tasman Bay and is managed as a conservation area by the Department of Conservation . Land access is via Boulderbank Drive at the north end of Nelson Harbor off State Highway 6 .

Geology and geography

The Boulder Bank is made of granodiorite , which comes from Mackay Bluff. It is still a matter of dispute how the gravel bank came about. Beach relocation is the most common theory of origin. The main argument against it is that there is not enough wave motion in Tasman Bay to move large rocks in a southwestern direction. Studies on the speed of movement of the stones have been carried out since 1892. The upper layer of the ballast then moves 7.5 meters a year.

Boulder Bank, panorama from Kaka Hill , 2007

The only access to Nelson Harbor was originally a strait at Arrow Rock at the west end of Nelson Harbor. The driveway was narrow and was increasingly narrowed by sandbanks. This proved to be an obstacle against the background of increasing sea transport to Tasman . Therefore, between 1903 and 1905, the Boulder Bank was pierced over a width of 61 meters. Today the “cut” is 150 meters wide and is dredged every six months to maintain a depth of 10 meters.

In 1862 a lighthouse was built on the western end of the bank.

literature

• ND Hartstein, Warren Dickinson: Wave energy and clast transport in eastern Tasman Bay, New Zealand in Earth Surface Processes and Landforms, 31: 6 (703–714) 2005. doi : 10.1002 / esp.1340
• Karen Warren: Rolling Stones: Nelson's Boulder Bank, Place in Our History and Hearts. , Nikau Press, Nelson 2009.

Web links

• Hilary Mitchell, John Mitchell : Te Tau Ihu tribes - The story of Boulder Bank . In: Te Ara - the Encyclopedia of New Zealand . Ministry for Culture & Heritage , November 15, 2012, accessed February 10, 2016 . 
• Maggy Wassilieff : Coastal shoreline - Nelson Boulder Bank . In: Te Ara - the Encyclopedia of New Zealand . Ministry for Culture & Heritage , July 3, 2013, accessed February 10, 2016 . 

Individual evidence

1. ↑ ^{a b} M. R. Johnston: Nelson Boulder Bank . In: New Zealand Journal of Geology and Geophysics . 44, 2001, pp. 79-88. doi : 10.1080 / 00288306.2001.9514924 .
2. ^ ^{A b} Cawthron Institute: History & Natural History of the Boulder Bank. Nelson Haven . Cawthron Institute, Nelson, New Zealand 1976.
3. ^ Mark Phillips: New Zealand Lighthouses . 2005. Accessed December 1, 2007.

Coordinates: 41 ° 14 ′ 3.9 ″  S , 173 ° 17 ′ 52.4 ″  E