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 Harbour. Haulashore Island was once a part of the Boulder Bank, but the Cut made it an island, and it is no longer connected to the Boulder Bank. The Boulder Bank separates Tasman Bay and the Nelson Haven and is managed as a scenic reserve by the Department of Conservation. Land access is gained along Boulder Bank Drive, signposted at the northern end of Nelson Haven on State Highway 6.
Geology & Geography
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, however, is the most accepted hypothesis for creation. The main objection for longshore drift is that 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.
The Cut was made to enable the Nelson port to allow the increasing demands of sea transport for the Tasman area. Construction started in 1903 and in 1905 a 61 metre wide entrance was operational. Today the Cut is 150 metres wide and dredged every six months to maintain a depth of 10 metres.
There is a small lighthouse which was erected in 1862. It is located near the port end of the Boulder Bank.
Boulder Bank Track
Time: 2-3 hr one way
A walk along the Nelson Boulder Bank is an opportunity not to be missed. The eight kilometre walk, from Boulder bank Drive to ‘The Cut’ takes 2-3 hours one way. The Boulder Bank is rough, dry and very exposed, so be prepared for all kinds of weather and wear strong shoes.
Access to the Boulder Bank is from Boulder Bank Drive (off Atawhai Drive (State Highway 6)) or by boat from Nelson. A ferry service is available from Nelson.
Places to stay
Camping is prohibited in this area. Private accommodation is widely available in the Waimea Basin.
About the area
The plains and low hills between Nelson and Motueka are known as the Waimea Basin. Tramping, hunting, watersports and walks through historically and ecologically significant areas await visitors.
The internationally-renowned Nelson Boulder Bank is a natural spit of boulders, formed of the debris of land slips from the Mackay Bluffs, swept southwards by sea currents over 10,000 years. The bank is 13 kilometres long, the last eight kilometres forming a spit which separates Tasman Bay from Nelson Haven. It’s width varies from 55 metres at high tide to 240 metres at low tide.
Maori camped on the bank and fished there. They used boulders from the bank – some up to 50 kg – to hammer the rough forms of stone tools from quarries in the nearby hills.
The shelter offered by the Boulder Bank was a major factor in choosing the site of Nelson. In 1848 a beacon was erected near the end of the bank and, in 1862, the cast iron lighthouse building that remains today. In 1906 a cut was made in the bank to allow easier passage to Nelson Harbour for shipping. ‘The Cut’ now separates Haulashore Island from the bank.
Plan and prepare
Be wary of sudden weather changes.
If boating in Nelson Haven, check tides and sea conditions before departing.
Credit: Wikipedia, DOC