- Boulder Bank
The Boulder Bank is a very unusual naturally formed land form in
Nelson, New Zealand . It is a 13 kilometer long stretch of rocky substrate which begins at theMackay Bluff and ends at the Cut of the NelsonHarbour .Haulashore Island was once apart of the Boulder Bank, but after the Cut being made is an island, and no longer connected to the Boulder Bank. The Boulder Bank separatesTasman Bay and theNelson Haven .Geology & Geography
The Boulder Bank is composed of
granodiorite cite journal | author=M.R. Johnson| title=Nelson Boulder Bank| journal=New Zealand Journal of Geology and Geophysics| year=2001| volume=44| pages=79–88] . 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 thatTasman 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 coursegravel movement have been estimated at 7.5 meters a year cite journal | author=M.R. Johnson| title=Nelson Boulder Bank| journal=New Zealand Journal of Geology and Geophysics| year=2001| volume=44| pages=79–88] .The Cut
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 meter wide entrance was operational cite book | title=History & Natural History of the Boulder Bank. Nelson Haven| last=Cawthron Institute| date=1976| publisher=Cawthron Institute| location=Nelson, New Zealand] . Today the Cut is 150 meters wide and dredged every six months to maintain a depth of 10 meters cite book | title=History & Natural History of the Boulder Bank. Nelson Haven| last=Cawthron Institute| date=1976| publisher=Cawthron Institute| location=Nelson, New Zealand] .Lighthouse
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