Tank Farm Lookout (Auckland)
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In between 10 other caches on/near the Tank Farm tuff crater walk way.
Tank Farm is one of the sites of three explosion volcanoes on the North Shore. Lake Pupuke, near Takapuna, formed in a series of explosions 1000,000 years ago. Onepoto Basin and Tank Farm craters, adjacent to each other in Northcote, date back 30,000 t0 40,000 years. They formed as a result of two massive explosions.
The two Northcote volcanoes threw up quantities of volcanic ash and pebbles which consolidated into rings of tuff around craters. Slyvan Ave, Exmouth Rd, College Rd and Akoranga Drive circle these tuff ridges. Both craters originally held fresh-water lakes, but as the sea level rose to its present level at the end of the last Ice age, the sea invaded the lakes and formed tidal lagoons which developed into mangrove estuaries (Onepoto basin has since been drained and filled to accommodate playing fields).
From this look out you can look down the length of the lagoon and onwards to the cone volcano of Devonport’s Mount Victoria in the distance.
Let your imagination go back in time. Consider the spectacle of a massive, cataclysmic volcanic explosion throwing dark clouds of red-hot ash and debris thousands of meters above you, blocking the sun’s light. The tuff crater of Tank Farm was formed when hot magma forced its way towards the surface of the earth and met a layer of subterranean water. The mixture of magma and water below the surface formed a mass of steam which propelled the magma through the last layers of the confining rock. It was a land-altering explosion of activity which lasted only a matter of hours. Volcanic ash and lapilli (volcanic pebbles) fell around the edge of the gaping hole. These, over time, consolidated into the ring of tuff you can see forming the high slopes around the edge of the lagoon.
The slopes now are dotted with buildings and residential and secondary vegetation, but deep below the tuff ring there are clues that suggest mature forest once grew in the valley prior to volcanic activity. Evidence of some of these trees was uncovered when the coastal edge of the lagoon was quarried in the 1950’s to provide fill for the Northern motorway and approaches to the Harbour Bridge. Hollow mounds were left where the tree timber had decayed below the tuff. The mounds showed that some trees measured 5 meters in diameter and rose almost to 20 meters before branching.
The name Tank Farm originates from the petrol storage tanks built during World War II. You can see the holes made by the tanks, down the path on the left, where it opens out onto a grassed walkway (on Left hand side of track). They are now providing sheltered habitats for birds
The cache is a 400ml camo’ed sistema container with the usual log book, pencil, and swaps.
Enjoy the view – best at high tide.
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Coordinates are in the WGS84 datum