4 March 2013, 4:00pm - Update; Volcanic Alert lowered to Level 1, Aviation Colour Code changed to Yellow.
Ash emission at White Island has ceased for the moment and the Volcano Alert Level is reduced to 1 with the Aviation
Colour Code changing to Yellow.
Observations in the last week have shown that a small ash cone has been built in the “hot lake” crater, which is the
current focus of activity. The ash cone is surrounded by a small moat of water.
It is likely that in the short term, activity will alternate between dry and wet eruptions. When drier conditions
prevail, like last week, some volcanic ash may be produced. If there is an increase in water near the vent then phreatic
(steam driven) eruptions may occur. The crater containing the lava dome remains unchanged.
Seismic tremor levels are currently low, which is thought to partly reflect the lack of water involvement in the current
activity. A gas flight on 26th February measured around 600 tonnes per day of SO2, and 1950 tonnes per day of CO2,
similar to other measurements made since the start of 2013.
White Island remains in a heightened state of unrest and the long term outcome of the unrest remains unclear. It could
lead to explosive eruptions and larger ash emissions, like in August 2012, or decline to background activity. In the
short term it is expected that activity will be variable, largely reflecting the influence of water on the style of
activity.
Background
Unrest at White Island began in July 2012, leading to explosive eruptions and ash emissions in August. A small lava
extrusion occurred in November, followed by phreatic, steam driven activity in December which continued through January
and February 2013. Minor ash emissions have been interspersed throughout this eruption sequence as conditions within the
craters have changed.
The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 1 indicates signs of volcanic unrest.
Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community.
Craig Miller
Duty Volcanologist
ENDS