Just 50km off the eastern Bay of Plenty coast, White Island regularly puts on a show, often followed by a sulphuric rotten egg smell that drifts ashore. Apart from scientists, the island attracts between 10,000 and 15,000 tourists a year, armed with gas masks and cameras, and a guide.
White Island's volatile activity is why volcanologists at GNS Science, based at Wairakei, never take their eyes off the volcano with the help of cameras and monitoring equipment.
Volcanologist Brad Scott has been monitoring and visiting White Island for nearly 40 years. Right now it is at Level 1 status, meaning a constant background activity. Anything just over Level 2 (moderate to heightened unrest with potential for eruption) makes Scott and his colleagues nervous about who might be landing on it.
A Level 2 or 3 (a minor eruption) will prompt GNS Science to send warnings via the media, Civil Defence and aviation authorities, local councils and social media. But that's all it can do. Legally, it cannot stop people landing on the island or sightseeing close by from a boat.
"We don't have a legitimate mandate to stop people," Scott says.
White Island has remained at Level 1 since its last minor eruption in August last year, following another at the same time in 2012.
Scott says tour companies licensed to take visitors to the island, one boat operator and three helicopter companies in Whakatane, Rotorua and Tauranga, make up their own minds after checking the volcano's activity. "It's the way New Zealand works."
Just as people decide whether or not to go flying, sailing or skiing based on weather forecasts, he says, visits to White Island are based on similar information. Anything between a Level 2 and 3 would put Scott off going. Increased activity is a warning but volcanologists can't say what will happen or when.
"You can't predict the time it will happen. It can transition into an eruption within just a few seconds, without warning."
GNS Science staff have had "terse discussions" with tour operators who have landed visitors on the island in conditions which make volcanologists anxious. "We don't visit but they still go."
Scott, who gives talks on NZ's volcanoes, has been mystified by an incorrect theory - that White island is the relief valve that stops earthquakes occurring elsewhere in the North Island including Auckland - that often comes up in question time.
While researching White Island's eruption history recently he found an 1860s' letter from a disgruntled MP objecting to Parliament moving from Auckland to earthquake-prone Wellington. The MP wrote that White Island was the relief valve that prevented earthquakes in Auckland.
"I realised that's the source of that urban myth," Scott says.
White island was first visited by the Maori in the early 1800s, who fished and caught muttonbirds, often cooking them in the steam from the crater vents.
The island has changed hands frequently since 1861 when it was thought to be sold by a Bay of Plenty chief to a European for "two hogshead of rum".
Europeans extracted sulphur from it in the 1860s but mining was interrupted by Tarawera's eruption in 1886. Now the only sign of human occupation are the remains of an old sulphur mine built in the 1920s.
In 1913, a sulphur mine was set up at Troup Head with railway tracks, men's quarters, a dining room and manager's house. All that was swept away in the 1914 catastrophe.
The NZ Sulphur Company was wound up in 1934 and an Australian syndicate bought the island to produce salt "using fumaroles for the evaporation of sea water". That plan evaporated and the island was sold to an Auckland sharebroker, George Buttle, in 1936, and has been in the Buttle family ever since. Buttle decided not to develop it.
The island passed to his son, John, who passed it on, in trust, to his three sons, James, Peter and Andrew.
Andrew Buttle says he and his brother Peter once camped on the island, helping with research on muttonbirds. By day, the island was deserted, he says, but at night muttonbirds would come "crashing in" under the pohutukawa trees.
"We'd take blood samples after dark. You could walk right up to them and pick them up."
These days White Island is protected, as are its muttonbirds and gannet colony. Tour operators say they use trails near waterways so that during the next rain, footprints will be washed away.
Sole survivor
He was forlorn and hungry but alive when rescuers landed on White Island after the September 1914 eruption that claimed the lives of 10 miners and four camp cats.
Nicknamed Peter the Great, the cat made himself known to supply ship crew members who, being hampered by bad weather, arrived a couple of weeks after the eruption. Peter was the small settlement's only survivor.
The miners' camp had been either washed into the sea or covered by metres of volcanic mud and debris. The bodies of the men, and of the other cats, were never found.
