New Zealand volcano disaster: seismic warnings of a pending disaster

Questions emerge about the wisdom of allowing tourists on White Island given a recent uptick in seismic activity there.

Tourists watch the volcano erupt. Picture: Michael Schade

White Island is one New Zealand’s most active volcanoes, but Monday’s dramatic eruption appears to have been the deadliest for almost a century.

Scientists had noted an uptick in volcanic activity on the island, a tourism attraction about 50km offshore from the North Island in the Bay of Plenty, over recent weeks.

READ MORE: LIVE — Follow the latest from the tragedy in New Zealand | No signs of life after NZ volcano tragedy

GeoNet raised the alert level on White Island from one to two on November 18, noting an increase in the amount of sulphur dioxide gas, which originates from magma deep in the volcano.

The volcanic tremor had also increased, from weak to moderate strength, while the island’s crater-lake level had been rising since August and geyser-like activity was recorded.

Volcanologists who keep a close eye on the grumbling leviathan say such activity is often followed by a calmer period, with alert levels often up and down.

Several experts said that while questions might be raised about the wisdom of allowing tourists on the volcano, it was often impossible to predict such sudden, catastrophic eruptions such as Monday’s, which spewed an ash plume 3.6km high.

A White Island Tours boat rescues tourists. Picture: Michael Schade

“Sudden, unheralded eruptions from volcanoes such as White Island can be expected at any time,” said University of Auckland volcanologist Shane Cronin. “Magma is close to the surface, and the heat and gases from this heat the surface and groundwaters to form vigorous hydrothermal systems ... eruptions can occur suddenly and with little or no warning because they are driven by the expansion of superheated water into steam.”

Chris Elders from Curtin University’s School of Earth and Planetary Sciences agreed. “There’s been fairly constant, low-level activity associated with that volcano and there may have been some signs of a small increase over the past few months,” Professor Elders said. “But there hasn’t been anything particularly dramatic, and these volcanic eruptions where steam and water are some of the driving forces, can occur with very little warning indeed.

“It’s a well-established tourist destination and people visit similarly active volcanoes all over the world. Stromboli, off Sicily, is a similar sort of volcano and people visit that. It’s difficult to say whether it’s a wise thing to do.’’

White Island volcano erupts.

The 2km diameter island, northeast of Tauranga on the North Island, is visited by tourists daily, with 10,000 visits a year.

Known by the Maori as Te Puia o Whakaari, “The Dramatic Volcano”, it is part of the “Ring of Fire” of volcanoes in the Pacific; its eruptions linked to plate tectonics.

“The Pacific Plate is moving to the west, underneath the plate on which Australia and New Zealand sit,” Professor Elders said. “That movement generates steam and heat and that is ultimately the cause of the volcanic eruptions.”

The volcano, about 70 per cent of which is under the sea, has been active for an estimated 150,000 years, but last claimed lives in 1914, when part of a crater wall collapsed and a landslide destroyed a sulphur miners’ village.

Professor Elders said survival could come down to sheer chance, while rescuers would face ongoing hazards. “For those on the island who experienced it, it would be a massive explosion and hot rocks and boulders rushing towards you and raining down on you,” he said.

Additional reporting: Agencies

This photograph courtesy of Michael Schade shows the volcano on New Zealand's White Island spewing steam and ash minutes following the eruption.