An earthquake swarm started near New Zealand's White Island volcano on Sunday, October 29, 2017. Over the next 3 days, GeoNet registered a total of 137 earthquakes, with the largest measuring M4.8 at a depth of 7 km (4.3 miles).
"It's a swarm of earthquakes that can happen from time to time," GNS volcano geochemist Agnes Mazot told Radio New Zealand. "There is nothing happening in the volcano… it's not happening in the volcanic edifice."
"We can have more today, tomorrow, it would not be unusual, but we don't know for sure how long it would take."
Mazot added that the quakes seemed to be a continuation of previous swarms of earthquakes in the area.
Volcanic Alert Level for the volcano remains at 1 – minor volcanic activity. However, an eruption may occur at any level. Hazards could occur on and near the volcano, and may include steam eruptions, volcanic gases, earthquakes, landslides, uplift, subsidence, changes to hot springs, and/or lahars (mudflows).
Sitting 48 km (29.8 miles) offshore, White Island (Whakāri) is New Zealand’s most active cone volcano which has been built up by continuous volcanic activity over the past 150 000 years. About 70%of the volcano is under the sea, making this massive volcanic structure the largest in New Zealand.
A sulfur mining venture began on the island in 1885; this was stopped abruptly in 1914 when part of the crater wall collapsed and a landslide destroyed the sulfur mine and miners' village; twelve lives were lost. The remains of buildings from another mining episode in the 1920's era are now a tourist attraction.
Although privately owned, White Island became a private scenic reserve in 1953, and daily tours allow more than 10 000 people to visit it every year. GeoNet monitors volcanic activity and visits the island around 10 times a year.
The most recent eruptive episode started in August 2012 with an explosive eruption on August 5, then a period of ash emissions. This was followed by heating in the Crater Lake and variable phreatic activity in early 2013 which removed the lake. By June the lake was re-established. A further explosive eruption followed on August 20 and again on October 11, 2013. Unrest continues to date.
White Island was in a state of frequent eruption from December 1975 to September 2000. It was its longest historic eruption episode.
Featured image: Earthquake swarm near White Island volcano, New Zealand. Credit: GNS
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