Scientists are keeping a close eye on rumbles at New Zealand’s most active volcano – with two key indicators of unrest at their highest level in three years.

Over the past few months, scientists have tracked a change in the amount of sulphur dioxide (SO2) pouring out of White Island in the Bay of Plenty, along with a shift in volcanic quakes.

“Both show an increasing trend and are at the highest level since 2016,” GNS Science duty volcanologist Yannik Behr said.

Analysis of the SO2, which came from magma in the bowels of the volcano, suggested a possible increase in gas passing through the volcano from depth.

READ MORE: The dramatic volcano: a decade of twists at NZ’s wild White Island

Volcanic tremors, meanwhile, could indicate anything from changes in the volcano’s geothermal system to surface activities such as geyser-like explosions that have been observed on the island over recent months.

But Behr said changes in these indicators were common and might be explained by increased unrest or just general “variations” in background behaviour.

Meanwhile, the island’s crater lake has been rising since early August – reaching a point where it’s influenced some surface activity around active vents on the west side of the crater floor.

None of the other monitoring parameters, like water chemistry or ground deformation, had shown any changes.

Behr said while the recent pattern of signals had similarities with an active period that ran from 2011 to 2016, they also might be down to increased gas flux which led to geysering and lake level changes.

“The link between gas flux and future activity is not well understood and the subject of ongoing research efforts.”

The island’s Volcanic Alert Level remained at level 1, indicating a state of unrest.

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