White Island in the Bay of Plenty is showing signs of increased activity prompting GNS Science to lift the aviation alert from green to yellow.
GNS Science reports White Island’s crater lake recently started to re-fill and gases are now vigorously streaming through.
White Island crater lake on July 28, 2012. Photo: Volcanic Air Safaris.
The raise in alert affects pilots flying over and near the Bay of Plenty region.
“Airborne gas measurements show the discharge of some sulphur gases has increased. During the past few weeks there has also been some minor volcanic tremor,” says duty volcanologist Michael Rosenberg.
“During 2011 and early 2012 White Island’s crater lake slowly evaporated to expose steam vents and form two large muddy pools.”
Michael says between Friday, July 27 and Saturday, July 28 the lake level rose quickly by about 3 to 5metres.
“Vigorous flow of gas and steam through the new lake can be seen from the air.”
Michael says the lake has been inaccessible for many months and they have not been able to measure changes in its temperature or chemistry.
“Sulphur gases measured in the steam and gas plume have increased during the last three months but CO2 gas output remains at about the same level.”
Since early July there have been intermittent periods of volcanic tremor, including several hours early on Saturday, July 28 and during Monday and Tuesday this week.
Michael says tremor is not uncommon at White Island but earlier this year it had been at very low levels.
A recent ground survey showed the main crater floor is no longer subsiding and now may be slowly rising.
This phenomenon is typical for White Island’s activity, says Michael, but is the first substantial changes to occur in the last few years.
GNS advises extra caution should be taken, especially if approaching the crater lake and other active thermal features.