There’s money in brimstone. At least, that’s what a succession of companies over a 60-year period thought when they looked across the Bay of Plenty and saw White Island’s steaming vent. There was sulphur for the taking; the problem was, getting it out. Who would want to live and work on an active—at times hyperactive—volcano?
In the Depression, workers could not afford to be choosy about jobs. Even so, some of the men hired by White Island Products to work the sulphur mines baulked at the hellish panorama that greeted them. A number had only signed on for the free meal on the boat, and were totally dismayed by the sheer grey-brown crater crags shrouded in billowing, hissing steam. Breakers sucked hard on beach boulders. Acrid brimstone stung their eyes and throat. Some swore they’d never land—one even lashed himself to the mast and refused to get off until the boat returned to the mainland—but enough workers stayed to allow the company to continue mining for a further seven months.
Making the same trip by helicopter some 60 years later still holds some apprehension. Despite the fact we’re not staying more than a few hours, that is time enough for the volcano to reveal its violent, turbulent soul.
I am accompanying a team of volcanologists who are conducting one of their periodic surveys of the island. As we approach across the rippled sea from Whakatane, the island looks like a huge ship at sea, high prow to the west and smoking engine in the centre. Tilting the helicopter brings a shoal of electric blue maomao into view as they catch the light, and there, surging alongside, is the long white form of a whale, swimming powerfully through the surface waters.
Those waters are renowned for their yellow-tail kingfish and other big game species, and support a significant deep sea fishing charter community in Whakatane. But the area around the island abounds in marine life of all types, and is only slightly less diverse than the famed Poor Knights. There are occasional invasions of paper nautilus (a rare member of the octopus family whose females incubate eggs in a large fragile white shell), and very rarely a leatherback turtle swims in to inspect the bubbles emerging from submarine volcanic vents.
Divers have observed. fish sitting in these warm vents—looking for all the world as if they were enjoying an underwater Jacuzzi. At times, though, the vents are too hot for comfort: fishing boat skippers have reported lead weights on nets coming up melted after drifting across the vents, and have even claimed to have pulled in fish precooked and ready to eat.
Most of the visitors to White Island come not for the marine environment, but to view what is regarded as one of the world’s most interesting and accessible volcanoes. White Island is part of the Pacific “Ring of Fire,” which extends from New Zealand up through the Kermadec Islands to Indonesia, Japan, the Kuril Islands and right down the west coast of the United States. White Island is the north-easternmost of the central North Island volcanoes, collectively known as the Taupo Volcanic Zone.
The Maori know the island as Whakaari, “that which is made visible,” but a longer name, Te Puia i Whakaari, suggesting the translation “the geyser that appeared,” was recorded by French explorer Dumont d’Urville in 1827.
The legend of the island’s creation shows that local tribes Te Arawa and Ngati Awa recognised its wider volcanic setting. They relate the story of tohunga Ngatoro-iRangi’s walk south from Maketu, where the Arawa canoe landed in the Bay of Plenty, to the summit of Mt Tongariro. He had never seen snow before, and, thinking that the mountain’s whiteness was surf, he was surprised at its coldness. To save himself from death by freezing he shouted karalcia to the gods of Hawaiki to send “te ahi”—subterranean fire—to warm him. It travelled under the sea, steaming to the surface to form Whakaari before continuing through to Rotorua and Tongariro to save him.
The legend of Maui also mentions the origin of Whakaari. Maui burnt his hand touching the embers of a fire on the newly fished-up North Island. To cool it, he plunged his hand into the sea, setting forever the position of the steaming, boiling Whakaari.
The island’s isolation-48 kilometres from the mainland—has influenced its history. Ngati Awa, for example, tell of the island’s use as a place of banishment. Te Tahi-o-te rangi, an unpopular tohunga, was tricked into leading a fishing trip to the island, then marooned there. He managed to escape by chartering a whale (some versions say a taniwha) and returned to the mainland to shame his opponents.
Whakaari was also used as a refuge during intertribal warfare, especially when Hongi Hika and other Ngapuhi were rampaging through the area in 1823. Joe Mason, secretary of the Ngati Awa Trust Board, says that the appeal of Whakaari as a refuge lay in the hope that the Ngapuhi would not waste time making the dangerous journey to such an inhospitable place. The hope was ill-founded: Ngapuhi raiders had no hesitation in paddling to the island and destroying its refugees.
Besides its use as a place of exile or sanctuary there was another, more fundamental, interest in the is island’s thermal activity, and it was the hunters’ privilege to feast on them to get the outing off to a good start. They stayed until they had enough food, and it was taken back to the mainland and preserved in fat—in the olden times, in the birds’ own fat; in my time it was pig fat. They gathered a lot of food from the sea, too. There were big crayfish and hapuka and after they’d dried and preserved enough they went home.”
Whakaari’s springs, hot and cold, were also used for medicinal purposes: for healthy bathing, and to cure skin diseases, rheumatism and other ailments.
Captain Cook sighted the island in 1769, calling it White Island because “as such it always appear’d to us.” It is not clear whether the ash was white that day, whether he was referring to the steam plume, or whether the place reminded him of the Isle of Wight back home.
The first European to set foot on the island was T. Shephard, some time in the latter part of 1826, in the course of a coastal reconnaissance of locations suitable for settlement. He noted (and we retain his spelling) “four large active creters … the largest of these creters was burning furiously and the flames arrived near its mouth with an immense quantity of dark and light coloured Smoke of a strong sul-phureous smell.”
Peter Wood, a volcanologist with the Institute of Geological and Nuclear Sciences (IGNS) at Wairakei, thinks Shephard must have been mistaken, and that what he described as flame and smoke was merely incandescent material—”ash and rock heated enough to glow without catching fire. Reflection off steam might make that look like fire.”
Flame or no flame, the island made a deep impression on Shephard. He goes on to say, “It is remarkable that no living creature nor any vegitable substance was found in this valey. The high Mountain which serounds it is nearly pupendicular which together with the immense quantity of Sulphuric Smock Strikes the spectator with terror.”
Shephard also noted the presence of a boiling lake on the island (later drained by one of the mining companies) and was the first to list the island’s commercial possibilities,noting brimstone, iron stones and “a kind of Soft rock like pipe clay which most likely would be good for bleaching cloth and washing.”
It took 50 years before Shephard’s suggestion of exploiting the island’s resources was taken up, but when commercialisation came, it came with a vengeance. A newspaper article in 1878 estimated the amount of sulphur on White Island as being “many hundreds of thousands, perhaps millions of tons,” and proclaimed that “White Island is, in fact, another Sicily, and will probably be worked for generations to come.”
On such reports were built half a century’s-worth of overzealous hopes for fortunes in sulphur mining.
The history of the mining ventures is one of exaggeration, miscalculation, hardship, bravery and ingenuity. The costs borne by those willing to risk their money, and the conditions endured by the miners, were usually for little return.
In 1838, the island had been sold by Ngati Awa chief Apanui to Philip Tapsell, a local flax trader. The price is popularly recorded as being two hogsheads of rum.
Not everyone in the tribe was happy with the sale. A letter dated 1878 to Chief Judge Fenton of the Native Land Court from “Wi Patene and others” begins “To Mr Fenton. Friend. Greetings. This is an application from us to you for our island Whakaari as we are very (pouri) sorry about it and we were not aware of Apanui disposing of it, now we have been crying for it every year. It was sold to Te Tapihana [Tapsell] before we or our fathers knew anything about it.”
The grievance appears to have been recognised, for the document has “Whakaari Island having been sold clandestinely, apply for a rehearing” written on it. However, it seems there was no rehearing, and by 1885 the island had gone through a few more changes of ownership, and was in the hands of two Europeans, John Wilson and Henry Johnson.
Wilson busied himself that year experimenting with methods of fertiliser manufacture, staying for days at a time on the shores of his great natural laboratory. He obtained two punts for use on the crater lake, but they had to be built entirely without metal fastenings, because it was said that the lake water was corrosive enough to disintegrate a galvanised bucket within minutes.
Wilson found that the lake water was a strong solution of hydrochloric acid, while a stream which fed it was largely sulphuric acid. “Either of these acids can be used to reduce bones,” he noted. Wilson probably made New Zealand’s first acid-based fertiliser.
Satisfied with his preliminary tests, Wilson formed the New Zealand Manure and Chemical Company, published a prospectus full of wild claims about the island’s inexhaustible deposits of raw materials, and began producing fertiliser for the local market and crude sulphur for export.
However, by the end of his first year of trading Wilson had to admit that the company had not made a profit. He blamed unforeseen complications, including higher than expected production and transportation costs, an inability to break into the tightly controlled international sulphur market, and the difficulty of hiring workers at a time when confidence in volcanoes was low: Mt Tarawera had just erupted (1886) and lingering memories of the Krakatoa disaster three years earlier were doing little to encourage new recruits.
After such initially glowing reports of the island’s potential, this poor performance came as a great surprise. Wilson was held responsible by the shareholders, and the company folded.
Little extraction took place for the next decade, but in 1898 the project was revived, and for four years modest tonnages of sulphur were shipped to Sydney. There was a further lull until 1913, when the island was sold to Archibald Mercer and John Browne, acting on behalf of Canadian capitalists. The White Island Sulphur Company was formed.
The new company drained the lake, by means of a ditch to Crater Bay, to get at some seams of sulphur that had previously been found by drilling. It invested in wooden bungalows to house the men, a boiler house, three retorts (used to heat sulphur ore), a laboratory and a store, all at Crater Bay.
Like its predecessor, the company boasted that it would make a killing from the island. But the island drew first blood. John Williams, a 32-yearold fireman, died of burns when one of the large retorts, corroded by acids released from the sulphur, burst under steam pressure. Shortly afterwards, another fireman, Donald Pye, disappeared, with only his boots being found. Some say he fell into a fumarole; others, that he committed suicide.
Then, in 1914, Whakaari really showed who was calling the shots.
In September of that year, on one of his routine supply trips to the island, captain Albert Mokomoko was surprised that he received no reply to his boat horn. After waiting for a time, he went back to the mainland, thinking the men were on the other side of the island. A few days later, the company asked him to return and land. He found no sign of the miners or their buildings—everything, including the wharf, was buried under metres of mud and rock.
Volcanologists reconstructing the event years later have concluded that an avalanche of rock collapsed from a portion of the western crater rim on to the main vents and swept down across the crater floor, obliterating all evidence of human presence. The bodies and buildings were never found.
Remarkably, there was one survivor: the camp cat, Peter the Great. The cat returned to Whakatane, perhaps with one life less, but with unimpaired virility: many Whakatane cat owners trace their pet’s genealogy back to this hardy beast.
Following the 1914 avalanche, the volcano reverted to its usual repertoire of quiet rumblings, while the White Island Sulphur Company itself fell dormant. On May 31, 1923, Mercer acquired full title to the island and rebuilt the camp outside the crater on a flat area amongst pohutukawa trees at Ohauora. An engineer’s hut, dining room, recreation room, kitchen and cook’s quarters were added to the new camp, and then the route to work was picked out.
Volcanoes, by their very nature, are difficult places to get around. Steep ridges alternate with deep rainwater-eroded gullies. Because a trip by dinghy was not always possible, a precipitous path was traced into the ash up to the rim of the crater and down again to the works buildings; the deep, steep gullies were bridged by plank.
The men had the choice of travelling to work by land or sea, though sea was preferred. There were two boats powered by outboard motors, and the men would race each other to the work site. At this time, the raw quarried rock was being shipped to Tauranga for crushing and bagging—at a spot that would later be named Sulphur Point.
In early 1926, Mercer and his partner Miles tried to expand the business by wooing prospective investors and gaining the support of influential local people. George Raymond Buttle, an Auckland sharebroker, was engaged to distribute shares to the public. Because of financial problems stemming from the fact that the company was based in Canada, a New Zealand subsidiary, White Island Products, was formed, and once more a wildly optimistic prospectus was put out. “The deposits of material on the island suitable for crushing and marketing are immense. The crater walls, which rise to a height of 1000 feet, are composed almost entirely of this material [sulphur and gypsum], and they are sufficient . . . to provide an enormous output for many years to come.”
The new company hoped to procure money and gain exposure by getting other businesses to take shares and act as fertiliser distributors. One of the most promising of these was the New Zealand Co-operative Dairy Company, which was interested in fertiliser to improve the feed of dairy cattle, and thus milk yield. The stumbling block was that the benefits of the island fertiliser hadn’t been proved, and the Dairy Company decided instead to give its support to a tried and tested superphosphate manufacturer. White Island Products’ expected source of revenue disappeared.
High transport costs were also crippling the company. In bad weather, the 70-kilometre voyage to Tauranga could be treacherous. Once, in a northerly gale, Mercer records that the Paroto was blown 14 miles off course and was forced to “creep up the coast.” This was not an isolated occurrence.
In an effort to remain solvent, the company decided to concentrate its fertiliser production activities on the island, and erected a factory in Crater Bay. But even this failed to improve the profitability of the venture. Making an about-turn in 1929, the company instructed that work on sulphur extraction begin. Here again, they were beset by the same old problems. There were delays in the retorting process and, contrary to the optimistic reports, a lack of ore reserves. In desperation, the company switched once more to fertiliser.
Fundamental to the company’s difficulties was the question of whether the fertiliser actually worked. Its sulphur content was usually much below the figure of “nearly 50 per cent” mentioned in the prospectus, and while some reports of the fertiliser’s efficacy were glowing, others were less enthusiastic. Claude Sarich, who worked on the island during the last months of the operation, muses: “It was quite a racket really, as they used the sulphur mixed with volcanic ash as a fertiliser. Instead of helping growth, the fertiliser would burn the grass off the paddocks.” Certainly, no weeds were ever found on the crater floor area.
The men earned two shillings an hour—a good wage at the time. The money wasn’t paid at the island (presumably to discourage gambling) and board and credit at the company store on the island were deducted from it.
Remuneration had to be good, because conditions on the island were next to impossible. In the constantly corrosive atmosphere, the men spent time coaxing reluctant engines to work, trying to bore through hard ground to reach liquid sulphur and quarrying rock. The bore pipes sometimes became jammed with solidified sulphur, and the men would spend the rest of the day cleaning them with a blow torch. Pipes corroded in the ground and simply fell apart, never to be retrieved. On occasions, liquid sulphur fountained into the air, splattering over and clogging surrounding machinery. The men had rasping coughs, their throats and nasal passages burned with the acid gases.
Lips, teeth and hair became salty and gritty from the constant pit-pat of ash. Every time a blustery wind caused the acid steam to overwhelm the work site, the men had to get down on the ground to breathe the cooler, clearer air at the surface. Clothes disintegrated rapidly. Despite the heat, wool, with its layer of natural oils and grease, was the only practical material to wear.
There was no refrigeration on the island, so when large joints of meat came off the supply boats, the cook would half-cook them and then drop them into vast tins of fat to keep. In emergencies, when the boat had not been able to land for a while, hapuka or strong-tasting gannet were served up relentlessly. Ralph Bryenton, a mechanic during the last months of the operation, passed so much rice unwillingly between his lips that he has never eaten it since.
Meat was available on the hoof,in the form of a small flock of sheep kept for lean times. They, too, had much to endure. The only grass on the island was a tough, unpalatable tussock, so the sheep grazed instead on the leaves of taupata (a type of Coprosma). The last sheep shot on the island is said to have had a 12inch-long fleece that was tinged orange next to the skin—no doubt due to the heavily mineralised environment.
Crayfish were a choice meal, and sometimes as many as 70 were served at one sitting. Occasionally, after a stormy night, there were muttonbird eggs to eat—the birds would lay their eggs before reaching their burrows, and all the cook had to do was collect them in their dozens from the ground. There was no fresh water on the island, so drinking water was brought in by boat—sometimes in badly washed petrol tanks—and stored at the factory.
Leisure activities included billiards and home brew competitions, reading from the company library and listening to the crystal radio set. Some of the men carved pohutukawa and painted island scenes on paper nautilus shells.
The Depression struck the final blow to the still profitless mining concern, and it went into liquidation. It appears that ICI, the chemical giant, took over the company’s assets—including the island—but was not interested in reactivating the sulphur operation. The present owner of the island, John Buttle, tells how his father acquired a volcano. “My father was present at the meeting when a Mr Buchanan took over the island on behalf of (as he thought) ICI. As they went out my father said to Buchanan, ‘What are you going to do with the island? Work it? Sell it?’ Are you interested?’ asked Buchanan. ‘Yes,’ my father replied. ‘I’ll give you £100 for it.’ Buchanan snorted in disgust.
“Subsequently, the island was put up for tender. My father tendered on the second occasion and was successful—though he never disclosed the amount to me. Asked by the press why he had bought it, he said he liked the idea of owning a volcano.”
John Buttle shares his father’s enthusiasm for the place, and plays an active role is all island matters,whether to research, tourism or conservation. He has taken part in a gannet census, and even joined a Russian research vessel working around the island. While happy to be perhaps the only man in the world to own a private volcano, he thinks that, in the long run, the government may be the most logical owner.
For now, Buttle has no plans to sell, and he makes no money from the island. He simply asks a $10 donation for charity from each person who lands there.
White island always in‑spired ebullient descriptions of its wonders. The introduction to a 1930s article effused: “Sylvan Beauty side by side with an Inferno of Fire . . . Teeming Wild-life rubbing shoulders with the Breath of Death—Sea-birds’ Love Call mingling with Volcano’s Roar.” Poetically inclined explorers coined colourful names for rock and ash formations, among them Lot’s Wife, Schubert’s Fairy and the Seven Dwarfs.
But for all its beauty, the island is a hostile place—and not just for humans. Resident plant and animal communities maintain a tenuous hold on the flanks of the volcano. There are three main types of plant community: pohutukawa forest, scrub and small herbs associated with the gannetries. The pohutukawa community enjoys the distinction of being the simplest forest in New Zealand.
White Island suffers from the deficiencies of both an island and a geothermal area. Island vegetation is always a little less complex and less diverse than vegetation on the mainland, due to long distance seed dispersal difficulties, but researchers investigating plant distribution have compared equal-sized plots (of 100 square metres) within forests, and found that while nearby Mayor Island typically has from 9 to 14 native species, and the geothermal site Taheke (near Rotoiti) has 8, White Island’s total has dropped from 5 in 1967 to 2 in 1990: pohutukawa and flax.
It is remarkable that plants can survive there at all. They grow in consolidated ash, which, though more conducive to growth than other volcanic rocks, such as lava, is still a far from satisfactory soil. It is rich in phosphates but very low in nitrates, and has a low pH.
While the roots struggle in the hostile soil, a silent death is also being rained and blown on to the plants from above. No dramatic scenes of burning incandescent clouds are acted out here; rather, leaves are quietly and mercilessly blotched and burned by rainwater which has turned to acid, they are surrounded by corrosive gases and fumes which interfere with all vital processes, and their leaves are smothered in wet sticky ash. If they survive all that, the smaller plants also have to contend with the occasional complete burial in ash.
At present, the New Zealand ice plant is the second most successful species after pohutukawa, because its adaptation to salty environments also helps it cope with the other toxins. Pohutukawa galvanises its dormant buds into action for a sprouting spree after it has suffered any trauma, but the problem it faces (which, paradoxically, makes the island such an interesting place for botanists) is that the damaging activity repeats itself time after time. Since the baring of Tarawera’s slopes to new colonisers, plants have had an uninterrupted 107 years to knit a soil together, shade each other and get hold. At White Island the clock is continually being set back to zero.
The oldest trees on the island have been aged by ring counting at 180 years. Trees of widely varying size have been found to be the same age; the small ones were found at harsh sites, directly exposed to the prevailing southwesterly winds and thus facing the brunt of the acid-laden plume. Their rings were much closer together than were those of larger trees at more protected sites.
The number of birds seems to be stable, at between five and six thousand pairs, putting the island’s importance as a nesting site on a par with that of Cape Kidnappers.
Gannets are plentiful at three sites along the island’s southern coast, and are also found on the Club Rocks, which lie just offshore. The rocks were named by miners who observed a number of apparently idle birds standing on them, and decided it was a “bachelors’ club” of unpaired individuals.
Gannet nests are regularly spaced guano mounds lined with seaweed and the few local plants. The birds don’t seem affected by the acid atmosphere—in fact, they live in their own blue haze of ammonium chloride, the result of ammonia in the droppings reacting with volcanic hydrochloric acid.
Vic Davis of Ohope has been making the annual gannet-banding pilgrimage since its inception in 1958. His faded photographs and newspaper clippings evoke an era, before helicopters and cellphones, of seamanship and ingenuity, expeditions, camps and wide-brimmed hats. His observations give a detailed picture of the conditions the birds must endure:
January 1983: Pohutukawa forest rotted and many trees on groundgannetries now have no shrub protection from wind. Sea temperature 10° lower than normal—food supply not plentiful. Strong westerlies made landing very difficult. A breeding disaster for the birds.
February 1989: The unusual amount of rain contributed to surprisingly good conditions on gannetry. Volcanic dust and guano was not present to any noticeable extent on nesting sites, resulting in “squeaky clean” birds . . . One disgorging after banding was cleaned up by a flock of 30 red-billed gulls.
January 1991: Heavy showers of rain fell and the response of the juvenile birds was remarkable—all 2000-plus flapped vigorously!
From the helicopter we have a gannet’s-eye view of the birds as they circle around their home: yellow-white dots against a bright green background of ice plant.
Dropping lower towards the island, we see the Island Princess approaching, with about another hour’s journey to go. The tourists—mainly locals and backpackers—will be able to go ashore today because the sea is calm. The more expensive helicopter trip tends to attract overseas tourists and people who have come to this part of the country specifically to visit the volcano.
We let out one of the volcanologists high up on the crater wall at the seismograph—he will have to slide and pick his way back down. We then glide over the edge of the crater, drop down to the sea and fly between the two large rock outcrops of Troup and Pinnacle Heads, skimming the boulder beach before settling lightly on the ash.
As the rotors slow and stop we take out gas masks and helmets and step outside. Except for hissing fumaroles and gulls’ cries there is silence. Our feet make no sound, but leave many prints as we walk. All around, old footprints have been preserved, with coloured contours of volcanic ash and salts clearly defining their shapes. Whenever the plume blows our way, we are engulfed in a cloud of acrid choking gas.
Regular monitoring of the island’s volcanic vicissitudes dates back to 1967, when scientists set up the first “level survey net,” still used today. The net is based on a series of marker pegs around the floor of the crater which are used as permanent reference points for repeated surveys of the ground deformation (or changing height) of the crater floor. Such observations allow volcanologists to study, rather than merely record, the island’s eruptions.
Additional information from the sampling of gas escaping from fumaroles, from magnetic field measurements (which reveal the changing magnetic properties of rock as it is heated or cooled), gravity measurements (which vary according to whether a solid or liquid is beneath your feet) and measurements of the intensity of tremors supplements the level survey data and helps the scientists formulate a model of what is happening down below.
White Island’s inner furnace is fired by the intense heat and pressure produced as one huge section of the earth’s crust, the Pacific plate, is forced under another, the IndoAustralasian plate. New Zealand rests precariously on the edge of the latter and is being jolted and pulled apart by the violent drama beneath our feet. Rock, layers of seafloor sediment, shells of dead sea creatures and seawater are dragged down into the earth’s mantle—the high-temperature rock layer below the crust—and are partially melted. This semi-liquid magma, being less dense than solid rock, becomes buoyant and moves upwards, forcing its way through fractures and weaknesses and emerging to form volcanoes. After it has been erupted this rock cools to form andesite. Tongariro, Ngauruhoe, Ruapehu, Mt Edgecumbe, Maungakakaramea and Pihanga are of a similar material (as distinguished from the volcanoes of Auckland, for example, which are basaltic—see Issue 16).
But White Island has a number of unique features which make it a perfect natural laboratory. Firstly the vent is actually below sea level, but shielded from the sea by high crater walls. Secondly, although it is an island surrounded by seawater, the vent is chemically sealed from it, and this sealed zone traps an acid hot water system which is derived from rain water and magmatic water. Thirdly, the whole volcanic system is compressed into a vertical distance of about 500 metres—compared to distances of about five kilometres in other volcanoes. Lastly, the island is easily accessible: researchers are spared a steep climb up and slither down to get to the crater. For these reasons, the island has been given an A-grade classification of international scientific importance, and has become the subject of a joint research project between the IGNS and the Geological Survey of Japan. This research should in turn become the basis of a two-year drilling project to find out more about how the hydrothermal system operates.
White Island is like a large saturated sponge, set permanently on a red hot element of magma and continually being refilled with rainwater, which it is constantly boiling off. But during the process, the element and water are reacting with each other. The element is changing the composition of the rainwater, and parts of the element are slowly being eroded away by the corrosiveness and explosive vaporisation of the liquid.
The hot volcanic gases from the magma body mix with the trapped rainwater to produce a highly aggressive hydrothermal concoction containing some of nature’s most acidic liquids. These liquids then attack and break down surrounding rock, further changing the balance. If the volcano were not so changeable, a stable hydrothermal system might form, but with the magma continually supplying acidic gases, the attack continues.
Seawater seeping in never reaches the cauldron inside. It gets only so far before the heat from the magma causes the calcium in it to join with the sulphates in the hydrothermal system. Mineral crystals of anhydrite and gypsum grow in the cracks and pore spaces of the rocks, slowing and eventually halting the trickle.
Although the surrounding watery archives of marine sediments tell us the island has been active for over 50,000 years, recent recorded history (from 1826 to the present) shows that the most active eruptive period started in 1976, as a result of the rise in 1973 of a relatively small body of magma (ten cubic kilometres) to only one kilometre beneath the surface—a very shallow depth.
The movement of this heat into the water-saturated debris caused an explosive flash—as if water had been dropped on to an electric hotplate. The hot gases streaming from this magmatic heat source continued to wear away chunks of the magma and erode particles from the loose wet walls of the conduits that lead to the surface. These rock and ash particles were carried upwards in a flurry, appearing to onlookers as part of the volcanic plume above the island.
During 1976, a lot of the water in the crater system was boiled off. Then, from December 1976 to March 1977, steam explosions turned bits of rock into ash and ejected them. So much material was erupted that the roof of the resulting chasm was unstable, and the whole nearby area collapsed into it to form so-called Christmas Crater and new blockages. In March, when the system was a lot drier and the magma very near the surface, strombolian eruptions occurred, showering volcanic bombs, fresh ash and blocks over the crater floor.
The surface of the crater floor is a light crust formed by repeated flecks of ash piling into minute crusty mounds and baking together. When knocked on lightly, it makes a hollow sound, but a heavy boot cracks through to either dusty powder or slippery mud underneath, depending on whether there is any steam seepage nearby. The ash colour varies from khaki-green (when it contains a lot of salts and chemicals) to pinky red (when the iron constituent has been oxidised) to the grey of cooler mixed rubbly ejecta, and fresh brown—straight from the magma.
The plume is electrically charged, the result of movement of hot, dry ash particles in the eruption column, and it is impossible to radio through the plume from the helicopter to the mainland. Static electricity can also build up on the surface. On one occasion, IGNS vulcanologist Bradley Scott, working near the main vent, bent down to pick up his tape measure, was jolted by static and nearly threw it into the vent. Repeated efforts to either pick it up or to touch the dry ground had the same effect.
Vic Davis, watching the island through binoculars one night from his home at Ohope Beach, saw a different electrical phenomenon: unusual golden zig-zag lightning within the cloud. “It was just like the lightning reported by eye-witnesses at the Tarawera eruption,” he says.
Having a volcano in their back yard is a matter of concern, if not healthy caution, for many Bay of Plenty residents. On crystal clear mornings, particularly after the island has been shrouded in rain for a week, the IGNS can expect a brace of calls from residents and the media to enquire about the volcano’s state, and whether there has been an outburst.
There is no denying the potential threat from White Island. Visitors to the island are, of course, at greatest risk. Explosions happen several times a year, without warning, hurling rocks on to the crater floor area—which is pitted with numerous impact craters of about one metre diameter—and these would certainly kill anyone they landed on. Changes in wind direction often overwhelm a party with blinding and stinging ash and gas-laden clouds. The Civil Defence Scientific Advisory Committee has produced a series of booklets warning about volcanic hazards in general, and the White Island edition suggests a macabre possibility: “Volcanic gases at White Island are discharged at high temperatures (100° 800°C) so that anybody falling into a vent would be rapidly cooked, an unwelcome prospect when blundering about in a steam cloud with eyes shut against acid drops!”
Apart from the collapse of part of the crater wall (which is unlikely, having happened only once in recorded history, in 1914) the only other catastrophe a visitor need fear is a pyroclastic surge. These occur as a result of groundwater-saturated crater floor material falling in on top of the magma and causing a steam explosion and eruption column. The pyroclastic surge occurs when part of the plume becomes too dense to remain buoyant in the atmosphere, and collapses. The hot ash and gas falls, gathering enough speed to rush along the ground at speeds of up to 200 kilometres per hour. (In 1902, the whole town of St Pierre, with its 30,000 inhabitants, on the island of Martinique was scorched to the ground in a matter of minutes by a pyroclastic flow.)
Such nightmare-inducing possibilities should, of course, be kept in perspective. White Island is changeable indeed, but eruptions are characteristically continuous, low-key affairs. Many scientists and tourists stand watching and photographing eruptions as they happen. One report tells of people gazing out to sea and turning around to see a billowing black eruption cloud that had silently risen up from the depths behind them.
Helicopter pilot Robert Fleming, who flies visitors to the island hundreds of times a year, has been stranded on the island only once, in January 1992, when the wind changed direction and “big drops of acid gunk” started to rain down on the helicopter, making take-off impossible. He and his guests ran for shelter in the works buildings to radio for help, and another helicopter collected them. The damaged helicopter was retrieved the following day, and delivered back to the mainland slung underneath the rescue machine.
Fleming has also experienced sonic booms at the island, caused, say volcanologists, by gas from a shallow body of magma expanding out of a small vent at high velocity. “It was a daunting experience,” he says. “The booms were happening every ten seconds and the ash particles in the plume meant that I could see the air contracting and expanding as the shock wave went through it.”
Occasionally, White Island ash makes it to the mainland, but no eruption in 166 years of recorded history has been large enough to make much of a mark there. Nevertheless, geologists believe there is potential for a large eruption because of the size of the magma body. Research shows that the island pumps out 400 tons of sulphur dioxide per day, and 400 megawatts of heat. Assuming this output has been constant over 16,000 years, the magma volume must be several tens of cubic kilometres. If a large proportion of this were to be erupted, the scale of the event would be a lot bigger than previously experienced, and would threaten the coast with tsunami and a fallout of ash and pumice.
Another scenario involves large volumes of seawater entering the hot vents on the island, triggering a massive explosion and resulting in a tsunami large enough to overwhelm the entire Bay of Plenty coastline.
Could we see another Krakatoa? “It’s unlikely,” says Bradley Scott. “Volcanoes tend to be creatures of habit, and nothing like this has happened at White Island before. The vent edge is 30 metres above sea level and 700 metres from the beaches, and water doesn’t run uphill. During the Edgecumbe earthquake (magnitude 6) the vertical displacement at the centre of the fault trace was only three metres. We’d have to have a quake of greater magnitude, centred on White Island and fracturing the island enough to let the water in.”
As we climb back into the helicopter, people are coming ashore in an inflatable, trousers rolled up and bare-footed. My camera and hands smell strongly of sulphur, all my clothes feel soft and soapy, and I’m tired from five hours of a burning throat and eyes screwed up against the constant shower of ash.
Even so, as we hover over Whakaari’s scarred countenance before leaving, I find myself agreeing with former owner George Buttle: “Strange as it may seem, the island is unbelievably beautiful and beyond description. Surely it is one of the wonders of the world.”