Lake Taupō (file photo). Photo: 123rf
GeoNet has increased the alert level for the volcano below Lake Taupō, which caused the largest eruption on Earth in the past 5000 years when it last exploded about 1800 years ago.
In a statement, geological agency GeoNet said it had detected almost 700 small earthquakes below Lake Taupō, the caldera created by the giant volcano, and had raised the volcanic alert level to 1 from 0.
The volcanic alert system is based on six escalating levels of unrest, but Geonet noted that eruptions could occur at any level, and levels might not move in sequence as activity could change rapidly.
The Taupō volcano spewed more than 100 cubic kilometres of material into the atmosphere when it last erupted around 200 BCE, devastating a large area of New Zealand's central North Island in a period before human habitation. Geonet said the eruption was the largest on the planet in the past 5000 years.
GeoNet added this was the first time it had raised the Taupō Volcano alert level to 1, but this was not the first time there had been unrest and said the chance of an eruption remains very low.
"The earthquakes and deformation could continue for the coming weeks or months," it said.
Team leader Nico Fournier said level 1 indicated "minor unrest" but with the earthquakes and deformation it was considered the "appropriate" setting.
He said only two of 29 eruptions at Taupō have been large, the rest have been small, probably similar to what happened at Ruapehu in 1995-96.
Lake Taupō not only has a large volcano, it is also crossed by some large faults which cut across the whole region - known as the Taupō volcanic zones.
"When we do have earthquakes occurring inside the lake they are either occurring along some of those faults or they are occurring around the body of magma - those molten rocks which we know are under the surface at depth since the last eruption."
Scientists were trying to understand where they were occurring and which faults they were crossing, Furnier said.
Scientists were also keeping an eye on Whakaari / White Island after volcanic ash and strong gas was detected in the crater, RNZ reported yesterday.
In 2019, Whakaari suddenly erupted, spewing steam and ash, killing 22 people and seriously injuring 25, mostly tourists.
- Reuters