Volcanic Alert Bulletin TON-2013/04 - Tongariro Volcano

6 August 2013, 3:00pm - Very small earthquakes beneath Tongariro; Volcanic Alert Level remains at Level 1 (no change); Aviation Colour Code remains Green (no change)

During the past two weeks, the GeoNet seismic network has detected a few very small earthquakes beneath Mt. Tongariro. These events have been recorded only on a few seismic stations and are too small to be precisely located.

GNS Science said the earthquakes could simply be part of the background unrest typical of most active volcanoes. The earthquakes are of interest at this time because there have been so few at Tongariro since November 2012 and potentially could signal changes occurring inside the volcano.

The amounts of carbon dioxide and sulphur gases emitted from Tongariro have remained at low levels since the start of this year and are about half the amount produced after the November 2012 explosion. These conditions, and the small number and small size of recent earthquakes are not sufficient to alter the unrest status of the volcano and GNS Science has not changed the Volcanic Alert Level from 1, or the Aviation Colour Code from Green.

Te Māri has had no eruptive activity since an explosion on 21 November 2012 although an eruption could still occur with little or no warning.

Through the GeoNet project, GNS Science continues to monitor Tongariro for any new earthquake activity or changes in volcanic gas concentrations, and keeps a close watch for any visible changes.

Background

Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community. Code Green indicates that a volcano has no eruptive activity.

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.

Michael Rosenberg
Duty Volcanologist

Contact: Brad Scott

 

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