Warning: This story contains some distressing details.
The Whakaari / White Island eruption prompted a massive nationwide health response, ranging from ambulance officers on the ground to the country's top burns surgeons.
At the time the volcano erupted there were 47 people were on the island - 22 people lost their lives and many received serious burns.
Hamilton resident Geoff Hopkins and his daughter Lillani were on board a tour boat that had left the island just before it erupted.
The boat turned around to rescue who they could from Whakaari.
Both are first aid trained and helped victims during the excruciating return to Whakatāne.
Geoff said there was little they could do aside from clean people's burns and offer comfort.
"The one person I spent most of the time with on the way home who was telling me 'I'm not going to make it', and to be able to give them some hope and reassurance of 'yeah you can make it, you will make it, your better days are ahead, many years ahead'."
University of Auckland volcanology professor Shane Cronin said the burns were horrific.
"The burns that kept on burning, and that's the problem."
He said there was a cocktail of chemicals in the volcanic material that added to the injuries.
There was fluorine, which acts as a poison in the body, while sulphur reacts with oxygen and water to produce more acid.
"Along with the hot material, scolding hot material, steam and also acid within it, the fluorine and the sulphur were then ongoing acids."
He called the circumstances of the eruption - where people were on the island on a hot summer's day - a worst-case scenario.
"So everybody was wearing t-shirts and shorts, and yes they masks - they were quite effective actually, remarkably effective - and they had some hard hats ... but it was a hot day and a lot of skin area was uncovered. Had the eruption occurred on a colder day or ... in winter time when people were more heavily clothed, there would have been a much, much better outcome."
The patients were first taken to Whakatāne Hospital before being dispersed to hospitals around the country, including Middlemore, Canterbury, Waikato, and Hutt.
Middlemore Hospital emergency department clinical head Dr Vanessa Thornton said the first 48 hours after the eruption were very busy.
The National Burn Service is based in the hospital, and staff raced to get prepared to care for victims by organising staff and equipment.
She said the need for hospital-level burns care outstripped the capacity available in New Zealand and 19 people ended up flying home overseas for treatment.
"We were lucky because many of the patients were from Australia so [we] were able to repatriate a number of the patients to their hometowns. It's a long, complex, operative and rehab process so for those patients it would be better to be at home for this," Thornton said.
St John psychologist Adele Saunders travelled to Whakatāne a few days after the eruption to support staff.
St John staff are familiar with treating burns but the eruption presented a whole new challenge - a high number of patients with a range of severe to life-threatening burns all at the same time.
She said they had dealt with burns before but it was the first volcanic eruption they had dealt with made worse by the smell of sulphur.
That made for a challenging working environment, she said.
"There would have been much more pain, the smells, it would have been lots of sort of emotionally provocative parts of the job that people would have struggled with in the moment and days after."
She believes no one is immune to the impact of trauma and staff are encouraged to seek support.
Saunders said the eruption had shown how resilient St John staff were.
RNZ
