Volcanic Alert Bulletin TON-2012/35 - Tongariro Volcano

Published: Mon Dec 3 2012 5:00 PM

Volcanic Alert BulletinTON-2012/35
Mon Dec 3 2012 5:00 PM; Tongariro Volcano
Volcanic Alert Level remains at 1
Aviation Colour Code remains at Yellow

No further eruptions have occurred at Tongariro since the explosion on 21 November. Gas emissions remain similar to those that have been measured over the last few months, and there have been a handful of small earthquakes under the Te Maari area.

GNS Science volcanologist Brad Scott said; “It is now a week and a half since the eruption on 21 November and we are continuing to monitor the volcano very closely. Over the weekend, we detected four earthquakes less than magnitude 2 on our seismic networks, at a few kilometres depth under the active vents”.

There have been a number of reports of activity on Tongariro over the last few days: this is mostly because the weather has been fine and good views of the steaming vents have been obtained, however, no eruptive activity has occurred.

Over the next week, the scenario considered most likely is that there will be no eruptions, however explosions could occur with little or no warning. Due to the continuing gas output an odour can expected downwind from Tongariro.

GNS Science continues to closely monitor Tongariro through the GeoNet project.

Background

Gas measurements were made on 27 November from an aeroplane. Sulphur dioxide emission rates were about 180 tonnes per day compared to 160 tonnes per day on 25 November and 150 tonnes per day on 30 October. Immediately after the eruption on 6 August we measured sulphur dioxide levels of over 2,000 tonnes per day. Unfortunately, high wind speeds during the flight last week meant that carbon dioxide could not be measured.

The GeoNet project has four seismometers within about 15 km of the active vents at Te Maari, which are used to locate earthquakes under the volcano. Larger earthquakes can be detected on instruments much further away.

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 1 indicates volcanic unrest, with departures from background levels.

Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community. Code Yellow indicates that volcanic activity has decreased significantly but continues to be closely monitored.

Brad Scott, Gill Jolly Volcanologists