GNS Science has this afternoon lifted Mt Tongariro's volcanic alert status to level one and aviation status from green to yellow amidst a suddeny rise in volcanic activity lately.
GNS says volcanic earthquakes - which they describe as "small" - have been recorded beneath Mt Tongariro with the sequence starting on July 13. While it soon declined it restarted this week on July 18 and the volcanic earthquakes have been increasing in number across Thursday and today, Friday.
"These indicate unrest at Tongariro and give reason to change the Volcanic Alert Level to Level One and the Aviation colour code to Yellow" says GNS in a statement released to WeatherWatch.co.nz this afternoon.
"As part of our routine monitoring of seismic activity, we have recorded several volcanic earthquakes at Mt Tongariro since July 13. These earthquakes are small (magnitudes <2.5) and have only been well recorded by a few of the seismometers in our permanent network. The earthquakes cluster in a zone between Emerald Crater and the Te Maari craters at 2-7km depth".
To better understand the significance of these earthquakes GNS are planning to:
Deploy portable seismic recorders around the epicentres of the earthquakes
Conduct sampling of selected hot springs, crater lakes and fumaroles in the area.
GNS says their historic seismic data has shown that these small volcanic earthquakes are common at Tongariro, but usually only occur at an average rate of 2 per yea - GNS has recorded more than 20 since July 13.
The statement from GNS goes on to say that Mt Tongariro is a volcanic complex that lies to the north of Ngauruhoe. It consists of numerous craters and vents. Te Maari craters lie about two kilometres east of Ketetahi hot springs on the north side of Mt Tongariro. The Te Maari craters are the last craters to be active on Tongariro.
Ash eruptions have been recorded from Tongariro from 1855 to 1897, as well as unconfirmed activity in 1926-27.
Volcano Alert Level has changed from 0 to 1
Aviation Colour Code has changed from Green to Yellow
GNS Science volcanologists are monitoring the unrest and further information will be released as necessary.
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