Published: Mon Mar 23 2015 5:00 PM
23 March 2015, 4:00pm - Volcanic Alert Level rises to Level 1; Aviation Colour Code remains Green (no change)
Seismic activity around Ngauruhoe has increased above the typical background level, indicating minor volcanic unrest. Consequently GNS Science has raised the Volcanic Alert Level to level 1 (minor volcanic unrest) from 0 (no volcanic unrest).
During the last two to three weeks there has been an increase in the number and magnitude of earthquakes being recorded by the GeoNet seismographs around Mount Ngauruhoe. Initial analysis indicates these earthquakes are shallow, occurring at depths of less than about 5 km.
The last significant eruption at Ngauruhoe was in 1975. Earthquakes are not unusual near Ngauruhoe, but it is some time since we last recorded significant numbers or events above magnitude 1. Similar numbers, but smaller events occurred in December 2014. Other swarms of earthquakes near Ngauruhoe occurred in 1983, 1991, 1994, 1995 and again between 2006 and 2010, but otherwise Ngauruhoe usually has little earthquake activity. The Volcanic Alert Level was raised to Level 1 in June 2006 and then lowered to Level 0 in December 2008 in response to the earthquake activity at that time. No other parameters we measure at Ngauruhoe (gas, temperature) changed during these times.
The current change at Ngauruhoe indicates the volcano has entered a state of volcanic unrest, like we have recorded several times in the last 30 years. No previous periods of unrest have resulted in a volcanic eruption. The outcome of this unrest is more likely than not that there will be no eruption in the short term, like during the 2006-2010 unrest. We continue to monitor Ngauruhoe closely and will release updated information as it is available or necessary.
The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.
The Aviation Colour Code for Ngauruhoe is Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.
Art Jolly Duty Volcanologist
Media Contact Brad Scott Volcanologist 07 3748211