A court has heard more people could have died in the White Island disaster if quick-thinking tour guides and tourists hadn't reached cover behind rocky outcrops and mounds.
The Whakaari White Island trial has heard how the 22 victims of the 2019 eruption died.
The court was read two so-called 'Section Nines', statements of facts agreed between the prosecution and defence.
WorkSafe is prosecuting the island's owners, the Buttle brothers Peter, James and Andrew, their company Whakaari Management Ltd, Tauranga Tourism Services Ltd and ID Tours New Zealand Ltd for failures under the Health and Safety at Work Act.
The first Section Nine related to passenger movements, the other focused on the health impacts.
The court heard 47 people were on the island when the volcano erupted in a pyroclastic density current (PDC) as steam, mixed with gas, volcanic ash and fragment rock in a sudden explosion at 2:11 pm on Monday December 9, 2019.
They were in three groups. Three of the 21 people in group 1 died. That group was halfway back from the crater.
A statement read to the court by WorkSafe prosecutor Samantha Forrest said: "The survivability of those in group 1 was bolstered by the eruption's relatively low velocity and dynamic pressure, the brief duration of the flow before it convected away from the crater floor and, above all, the actions of the tour guides and tourists to take cover behind the rocky outcrops and mounds of the island before the PDC struck.
"The outcrops likely provided a barrier to the flow and reduced the exposure of the body to the heat and the dynamic pressure of the current. Without these factors the health outcomes could have been much worse for this group."
Without this and the relative slowness of the eruption, the court heard that the health outcomes could have been much worse for this group.
Eighteen perished in the second group of 21 people. They were caught just 200 metres from the crater, having turned around just three minutes earlier.
The third group of five had come by helicopter from Rotorua and was 200 metres from the wharf when the eruption occurred. One man in that group died in hospital six months later, having received burns to more than 50 percent of his body, however three had reached the sea and submerged themselves, significantly reducing the injuries that would have been sustained had they been in the open.
The court heard the primary health hazards of PDCs included thermal injuries to skin and airways of the lungs, acid burns from the acid water in the crater lake, blunt force trauma from possible ballistic projectiles and other missiles, inhalation of hot volcanic gases and fine ash particles.
The court was told that, based on evidence from previous PDCs, such eruptions are typically too hot to survive for more than a minute or two.
