Underground explorers unlock shaft’s secrets
Nelson cavers believe they may have found the deepest vertical shaft in Australasia.
Long-time Kiwi caver Kieran McKay said the Bulmer Cavern cave system, under Mt Owen in Kahurangi National Park, was already the longest in New Zealand, at about 76 kilometres of explored cave. But the shaft could give it the honour of having the deepest single shaft as well.
A team of Nelson cavers, the Extreme Cave Team, recently attempted to reach the top of the vertical shaft, which McKay said was at least 300 metres deep.
Cavers found the bottom entrance of the shaft in 1998, and have been inching upwards ever since.
‘‘It could be the biggest shaft in the southern hemisphere. It’s definitely the biggest in New Zealand and Australia,’’ McKay said.
The deepest known vertical shaft in the world is a 603m drop in a cave in Slovenia.
Over the years, more and more of the Bulmer cave system has been mapped, and cavers have been able to explore further up the shaft, 50m to 100m at a time. During the recent expedition, the team got near the top.
‘‘There’s two frontiers in caving, and that’s climbing and diving,’’ McKay said. ‘‘Some cavers get to a big, deep pool, and for them that’s the end of the cave . . . same with a shaft, that used to be the limit, but now with light drills and things, we can make our way up.’’
There have been annual expeditions into the system every year since 1985, and McKay is quick to point out that he and his expedition this year were ‘‘just part of the story’’ that began with the cave’s discovery in 1984.
‘‘We explored about 67km of cave really quickly, that was in 1985 . . . in 1986, no-one showed up because they thought it was done, but we surveyed more, and we’ve gone in there every year since.’’
McKay said the shaft would eventually either lead to the surface, which he estimated was about 100m further up, or hopefully provide a pathway through to the northern side of the mountain.
He said he and other cavers exploring the Bulmer system were trying to find an elusive passage through to the other side of the mountain. There are several underground waterways in the system, most travelling to the south, but there is one that goes the other way and emerges about 10km to the north, which the cavers discovered using a dye drop test.
‘‘The known cave is within about a 4km stretch, but with 76km worth of caves all on top of each other,’’ McKay said. ‘‘We know there’s at least another 10km [to emerge where the north-running river comes out] – there could easily be hundreds of kilometres of caves. That’s what keeps us coming back.
‘‘We know more about the surface of the Moon or Mars than we do about these caves. They’re places where no person has ever been.
‘‘When Neil Armstrong put his foot on the Moon, the whole world was watching. When we step into one of these caves for the first time, it’s just us.’’