Caves are formed by natural processes such as the action of rainwater, waves, glaciers or lava (molten rock).
The most commonly explored caves are those where the underlying rock is limestone or marble. As water trickles through the soil and down to the rock, it absorbs carbon dioxide from the atmosphere and air gaps in the soil. This makes the water mildly acidic, so that it slowly dissolves calcium carbonate, the main constituent of limestone and marble. Over millions of years this eroding action can hollow out underground caverns, tunnels and streams stretching many kilometres. Water often still flows through them, and the streams can rise quickly with heavy rainfall above ground.
About 300 North Island and 250 South Island caves have been mapped. Most are in two regions:
However, caves are dotted around the country, usually where there is underlying limestone or marble.
Not all of New Zealand’s caves are in limestone or marble. Sea caves form in many types of rock along the coast, Auckland’s volcanic cones have tunnels known as lava tubes. These form when molten rock runs out of a lava flow, leaving walls and a roof which solidify to form a tunnel. In Otago, weathering in schist creates hollows. But most of these caves are shallow and do not form the huge, three-dimensional mazes found in limestone and marble.
Water that creates caves by dissolving limestone and marble also deposits calcium carbonate. This results in structures known as speleothems. The most well-known are stalactites (spears that develop as water drips from the cave ceiling) and stalagmites (spears that grow upwards from the cave floor). Crystals and other delicate structures such as cave coral also form.
Speleothems take thousands of years to form, and cavers use red tape to mark areas that are delicate and off-limits.
In 1966 cavers exploring a pot (a natural shaft) in the marble of Mt Owen reached the bottom at 53 metres, where they found a stranded possum. Expedition leader ‘St Francis’ Hardman put it in his pack and released it at the top. The cave was named Possumboot Shaft.
Organisms that have adapted to living in caves are often unique. Most life occurs close to the entrance, where there is still some light. In New Zealand most of these life forms are invertebrates (animals without backbones). Adaptations to life in the dark include no eyes or reduced eyes, a lack of pigmentation (camouflage is not needed), and long hairs or antennae to pick up vibrations from other unseen creatures (prey and predators).
It is common to find glow-worms – the luminescent larvae of the gnat Arachnocampa luminosa. A species of fern, Asplenium cimmeriorum, has been found at cave entrances around Waitomo and north Westland.
Over thousands of years, birds such as moa have fallen into some caves. Their bones, found on cave floors, have proved very helpful in identifying many extinct New Zealand birds.
Māori used caves sometimes for shelter, but mainly as burial grounds. For this reason many were sacred sites.
The earliest European explorer of limestone caves was probably Arthur S. Thomson. In 1849 and 1852 he collected moa bones from caves near Waitomo in the King Country. On 28 December 1887, Tāne Tinorau and Fred Mace floated down a stream into the Waitomo glow-worm cave on a raft of flax flower stalks, using burning brands to light their way.
Waitomo soon developed a tourist industry around the caves, with local Māori such as Tāne Tinorau acting as guides. It has been the centre of commercial caving since around 1900.
The government purchased the land in 1904 and in 1905 the Tourist Department took over the management of the caves. In the 1920s female cavers embarked on tours bedecked in smocks, bloomers and boots, and carrying lanterns. Small boats floated visitors into the Waitomo glow-worm cave, and walking tours took people into dry areas of caves. In 1981 the Waitomo Museum of Caves opened.
Black-water rafting – wearing a wetsuit and floating through a cave on a rubber tube – began at Ruakuri cave in Waitomo in 1987, offering tourists more than just a sedate walk through part of a cave. Tourism Holdings bought the rafting company in 2004. Ruakuri, which had been closed for 16 years for walk-through tours, was promoted as a spiritual experience, focusing on its Māori history. As the original entrance was considered tapu (sacred), a new entrance was built for guided walkers to enter the cave. In 2004 the Waitomo caves attracted around 400,000 visitors, including around 30,000 rafters.
In 1948 Europeans discovered the Te Ana-au caves, on the western shoreline of Lake Te Anau in Fiordland. The site has been developed into a tourist venture, with guided launch trips operating from Te Anau.
On top of Tākaka hill in Nelson, Ngārua Cave is open for guided tours.
Some purist cavers view the development of caves for tourism as exploitative. Most cavers have a strong sense of responsibility, carrying out all waste and not taking any souvenirs.
Caving is the recreational sport of finding and exploring caves. Speleology is the scientific study and exploration of caves.
Cavers would be the first to admit that they are an odd group. It takes a certain mindset to spend hours below the ground, often getting wet, dirty and cold, squeezing through narrow tunnels and abseiling down waterfalls. But cavers are underground explorers, and there are rewards, such as finding a deep passage where no one has ever been.
A group of cavers began exploring the lava caves in Auckland’s volcanic cones in the late 1940s. They soon progressed to limestone caves in the Waikato and at Waitomo in the King Country. Henry Lambert founded the New Zealand Speleological Society in 1949.
They faced many obstacles – few had cars, or even telephones to organise transport. Often exploring caves on farmland, they would sleep in shearing sheds or farmhouses. They used miners’ carbide lamps, and made rope ladders.
In 1955 the first headquarters were set up in an empty house near Waitomo. Many new caves and passages were found in the Waitomo area.
In 1957 a group of North Island cavers ventured south to Tākaka hill near Nelson, where a farmer led them to a hole he had never dared to enter. The cavers were ecstatic, estimating the maximum width to be 60 metres, and the depth 200 metres. They named it Harwoods Hole, after the original landowner.
On Christmas Day 1958, cavers were lowered into the abyss on a winch. David May, a schoolboy, was the first to go down, in a parachute harness with a steel seat. At a depth of 183 metres his feet touched bottom. Other members then explored 800 metres of passages.
A year later, the cavers returned, seeking a link to Starlight Cave, at the head of The Gorge Creek in the Tākaka Valley. They placed a green dye (fluorescein) in the stream at the bottom of Harwoods Hole, and it emerged four hours later in The Gorge Creek. Using explosives they blasted a stalactite block, allowing three cavers to make the first through trip. At 357 metres, Harwoods Hole (connected to Starlight Cave) was at the time the country’s deepest known cave.
Harwoods Hole is in New Zealand’s caving Mecca in north-west Nelson. Here, the marble within Mt Owen, Mt Arthur and Tākaka hill is riddled with subterranean passages. All but one of the country’s 30 deepest caves lie here.
The deepest cave is Nettlebed, on Mt Arthur. It was discovered in 1969, and in 1986 a connection was made with another cave, Blizzard Pot. Nettlebed has been mapped to a depth of 889 metres.
The longest cave is Bulmer Cavern on Mt Owen. Discovered in 1985, it has over 50 kilometres of explored length. Unusually, Bulmer is a dry cave, so explorers must carry water.
Some cavers aim to map a cave’s depth to 1,000 metres, and its length to 100 kilometres. The most likely place for this is in the Nelson marble country. Discoveries continue, and unmapped areas in existing caves await mapping. The major discovery since 2000s was Odyssey Cave on Mt Bell. In 2007 this had been explored to 296 metres deep and 1,700 metres long.
Success turned to disaster at Harwoods Hole in 1960, two years after cavers claimed it as the country’s deepest known cave. Group leader Peter Lambert was being winched out of the hole when he was killed by falling rocks. It was New Zealand’s first caving fatality. Lambert’s helmet was placed on a cairn at the bottom of the cave as a memorial.
At some caves with drowned passages, enthusiasts use diving equipment. In the 1990s at Waitomo, Kieran McKay and others found underwater tunnels to dry caves, adding to the length of known passageways there.
Divers have also explored Nelson’s Riwaka Resurgence, the source of the Riwaka River. They do not always find pockets of air, but sometimes just submerged tunnels and shafts.
Cave diving can be hazardous. On 20 May 1995 Dave Weaver died while in a shaft in the Pearse Resurgence, at the base of Mt Arthur in Nelson. Two divers recovered his body in January 1997.
Because it is always dark underground, one of the most important pieces of caving gear is a light source. Traditionally the main source was a carbide light generator. Calcium carbide was mixed with water to produce acetylene gas. At first the generators were miners' lamps, and the carbide was carried in the cap lamp. These were then replaced by lamps with carbide carried on a waist belt, which were still in widespread use in the 2000s. Increasingly though, carbide lamps are being replaced by headlamps with light-emitting diodes (LEDs). Torches are taken as a back-up.
Cavers wear helmets, polypropylene thermal underwear, overalls, and sturdy boots. They use an abseiling harness in caves with vertical sections, where caving is similar to rock climbing.
Safety is the caver’s top priority. Being underground, often many hours’ walk from the surface, means that some injuries can become a very real threat to life. Badly injured cavers must be carried out on a stretcher. There are now specialist search and rescue teams, but a vertical section or a tight squeeze can prove a major obstacle.
Cavers have strict safety practices. They always carry three sources of light and a map of the cave. The sport is a team activity and the emphasis is on cooperation. Even so, mishaps do occur – in New Zealand at least four people have died in caving accidents. In 1998 one of the country’s most experienced cavers, Kieran McKay, broke his jaw after falling deep within Bulmer Cavern on Mt Owen. Luckily Bulmer has few crawls and no tight squeezes. A major rescue operation swung into action, involving 80 cavers from around the country. McKay walked out of the final section on his own.
Enthusiasts use topographical maps when looking for new caves. Once these are found, new underground maps are drawn, detailing the structure of caves.
These maps are essential for return trips and those new to caves. They are published as the New Zealand cave atlas, with North Island and South Island editions. As caves are dangerous places for the inexperienced, entrances are not marked on topographical maps.
Dye tests are also valuable. A special green dye called fluorescein is placed in subterranean streams, and suspected springs or resurgences are monitored for traces of the dye. If it shows, this indicates that the stream feeds the spring, helping cavers to link caves with downstream drainages.
Two of the great challenges are to join two known cave systems, and to find more entrances. Sometimes a wind blowing out of the cave mouth is a sign of other entrances.
Trip by trip, tunnels and shafts are followed and surveyed – some with dead ends, others leading to huge caverns and further links.
Wacky cave names include the Hinkle-Horn Honking Holes and Goodbye Yellow Brick Road. Both are in Nettlebed Cave on Mt Arthur. Deep within nearby Bulmer Cavern, on Mt Owen, are Wellington on a Bad Day and Where the Wild Things Are.
The New Zealand Speleological Society first published the New Zealand Speleological Bulletin in 1952. It also publishes a quarterly newsletter, Tomo Times. Regional club newsletters (some with droll titles such as Wellington’s Sumpthink and Canterbury’s Cavity) feature upcoming trips and new discoveries. Delving deeper: half a century of cave discovery in New Zealand (2003), by Moira Lipyeat and Les Wright, is the definitive history.
Many clubs have websites featuring their latest trip lists and other news.
Acknowledgements to the New Zealand Speleological Society
Lipyeat, Moira, and Les Wright. Delving deeper: half a century of cave discovery in New Zealand. Waitomo: New Zealand Speleological Society; Christchurch: Hazard, 2003.
Grzelewski, Derek. ‘Tales of the underworld.’ New Zealand Geographic 34 (April–June 1997): 24–52.