An abrupt change at White Island in the Bay of Plenty at the end of July has continued, with the volcano now producing ash for the first time in more than a decade.
Thursday 9th August 2012
White Island volcano began filling with water on July 28th after more than a year with the crater lake at low levels with exposed steam vents. Volcanic tremor increased at the same time, with an associated increase in the output of volcanic gases. Vulcanologists’ observations over many years indicate that this is typical for White Island, but they noted that this was a significant change from activity noted in the last few years.
The abrupt refilling of the crater lake by about 5 metres overnight on July 27th and 28th was associated with a volcanic earthquake which indicated that an eruption might have occurred. The flow of gas and steam through the lake was noted alongside an increase of sulphur gas.
Volcanic tremor became more continuous from July 28th and a stronger episode was recorded overnight on August 4-5, ending in a volcanic earthquake at 4:54 on the morning of August 5th. One of the webcams on the island recorded an eruption, nicely lit by the moon, from the crater lake at that time.
This report by GNS Science contains images showing the plume rising during the eruption at White Island on August 5th.
At about 11:30 p.m. on August 7th, volcanic tremor at White Island sharply decreased. A few hours after, the plume changed from white to light brown, indicating that more ash was being emitted from the volcano.
This is the first time that ash has been produced by White Island since 2000, and vulcanologists think it may represent the start of a new phase of activity at the volcano.
White Island is popular with tourists who visit from the mainland. GNS Science warns that visitors to the island are at the highest level of risk since 2000, and suggest that caution should be taken when visiting the site. Scientists have now produced an ashfall plot for White Island if ash continues to be produced by the volcano.
Scientists plan to visit the island this week to sample fluids and gases and further assess the state of the volcano.
[Compiled from GNS Science bulletins published on the GeoNet website.]