|Photo: (George Novak/New Zealand Herald via AP)|
New Zealand volcano which caused the world's largest eruption of the past 5000 years is in danger blowing its top as alert level is raised
New Zealand scientists on Tuesday increased the alert level for the volcano below the country's biggest lake, which caused the largest eruption on earth in the past 5,000 years when it last exploded about 1,800 years ago.
In a statement, geological agency GeoNet said it had detected almost 700 small earthquakes below Lake Taupo, 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 notes that eruptions may occur at any level, and levels may not move in sequence as activity can change rapidly.
The Taupo 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 says the eruption was the largest on the planet in the past 5,000 years.
GeoNet added this was the first time it had raised the Taupo 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.
New Zealand straddles the boundary between the Pacific and Australian tectonic plates and experiences significant volcanism and earthquakes.
GNS Science, through the GeoNet program, continually monitors Taupo Volcano and other active volcanoes for signs of activity.
"While some of the earthquakes may be felt in areas around Lake Taupo, the deformation is currently only detectable by our sensitive monitoring instruments," Fournier said.
The earthquake sequence beneath the central part of Lake Taupo has continued, he said, adding almost 700 minor earthquakes, mainly at a depth of 4 to 13 km beneath the lake, have now been located.
"We interpret the ground uplift and earthquake activity to be caused by the movement of magma and the hydrothermal fluids inside the volcano. We have also sampled springs and gas vents around the lake for changes in chemistry that may be related to the earthquake and ground uplift," Fournier said.
While Volcano Alert Level 1 is mostly associated with environmental hazards, the potential for eruption hazards also exists, he said.