Published: Thu Dec 12 2019 1:45 PM
On Monday 9 December at 2:11pm an eruption occurred at Whakaari/White Island, with significant and devastating impacts for people on the island at the time.
Those affected by the eruption continue to be in our thoughts during this difficult time.
At 10:00am 12 December, GNS Science volcanologists reviewed all available data and updated the likelihood of an eruption that would impact beyond the vent area (marked in the image below) occurring within the next 24 hours.
Photo by Karen Britten, graphic by Danielle Charlton at University of Auckland. Click image to make it larger. The distance between the edge of the crater lake and the ocean at the bottom of the image is about 700m.
Their new calculation was that there is a 50-60% chance (medium likelihood) of an eruption occurring that could impact outside of the marked vent area within the next 24 hours.
The lower bound of the estimated chance of an eruption has increased slightly since yesterday (Wednesday 11 December 2019), from 40% to 50%.
How does this compare to previous estimates?
Since early 2013, likelihoods for Whakaari/White Island have been calculated via expert judgement as part of internal staff health and safety procedures.
The table below shows the expert judgement of likelihoods for time periods corresponding to when the Volcanic Alert Level (VAL) was at 1 (29 October 2019), and at VAL 2 one week prior to Monday’s eruption (2 December 2019). This is in comparison to the expert judgements conducted on 11 and 12 December 2019, after the eruption. There have been other expert judgements not listed here, including one carried out on 18 November 2019 when the VAL was raised to Level 2.
For 29 October and 2 December, likelihoods were calculated for 4-week and 13-week time windows respectively and have been converted in this table to reflect relevant 24-hour time windows for comparison.
The time periods used for the expert judgements vary depending on the level of activity at the volcano – when activity increases, we do expert judgements more often and for a shorter time window to reflect the changing situation.
For 11 and 12 December, eruption likelihoods have been calculated for a 24-hour time period. The table shows a large increase in eruption likelihoods over time.
The Volcanic Alert Level is not linked directly to risk and likelihoods but describes the level of current volcanic activity.
Timeline of activity
Our monitoring equipment continues to function and is providing us with continuous data on the volcano’s activity. Here is an annotated graph showing volcanic tremor over the last month recorded at one of our monitoring stations on the island. The 9 December eruption is shown in the red box. Also shown are the Volcanic Alert Levels for each time period.
Attributable to: Natalia Deligne, GNS Science Volcanic Hazard and Risk Modeller
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