Auckland Volcanic Risk: Deadly Base Surges May Reach Twice the Expected Distance

New research suggests that deadly base surges from a future volcanic eruption in Auckland could travel up to twice the distance previously estimated, posing a significant threat to the city and its residents.

Scientists have confirmed that the Hunga Tonga-Hunga Ha’apai volcano, which erupted in January, is the largest ever recorded with modern technology. This discovery highlights the potential dangers of volcanic activity, especially in regions like Auckland, where over 50 volcanoes lie dormant beneath the city.

Base surges—fast-moving clouds of hot gas, ash, and rock—are among the most dangerous volcanic hazards. They form when magma interacts with groundwater, creating a low-lying cloud that can move at tens of meters per second. Current estimates of how far these surges can travel are considered too conservative, according to research led by Gemechu Teferi, a volcanologist studying volcanic risk in Auckland.

Teferi's research, part of a program funded by the National Hazards Commission Toka Tu Ake and Auckland Council, has found evidence of base surges traveling up to 10 to 15 kilometers from volcanic vents in the Ubehebe Craters of California’s Death Valley. This area is similar in geological makeup to the Auckland Volcanic Field, suggesting that similar distances may be possible in Auckland.

“This is at least two times farther than previous estimates of how far surges can travel,” said Teferi, who is leading the research as part of his PhD. “We want to know if such distances are also possible in the Auckland Volcanic Field.”

The arid environment of Death Valley is ideal for preserving geological evidence that might otherwise be eroded by weather, vegetation, or urban development in Auckland. This makes the region an important site for comparison and research.

Auckland Emergency Management has already updated its response plan to include longer surge run-out distances. However, further studies are needed to determine whether these findings are applicable to the city’s volcanic field.

Dr. Jo Horricks, a resilience officer at the Natural Hazards Commission, emphasized the importance of the research. “If confirmed, it means the impacts of a volcanic eruption in Auckland would be potentially far greater than we previously thought,” she said.

Of the 53 volcanoes in the Auckland Volcanic Field, at least 42 show evidence of phreatomagmatic eruptions, which are known to produce base surges. Teferi has visited over 30 of these sites and selected nine with the best geological evidence of base surges for further investigation.

In the coming months, Teferi’s team will analyze rocks from the selected sites using a technique called Anisotropy Magnetic Susceptibility (AMS), which can detect microscopic evidence of past base surge flows. This data will be fed into a computer model to estimate the true distance these surges traveled in the past and to simulate potential future scenarios.

“Although unlikely, the impact of a volcanic eruption on Auckland is huge and base surges will be one of the biggest hazards,” said Horricks. “A more accurate estimate of how far these deadly clouds will travel can help councils with evacuation planning and insurers with estimating potential losses.”