New Zealand’s Mt Ngauruhoe volcano was recently upgraded to alert level 1 (some signs of volcano unrest) by GNS Science, following shallow low frequency earthquakes in the past month.
The upgrade was a precautionary measure, as the low frequency earthquakes occurring at the volcano can indicate increased movement of volcanic fluids or magma. As part of the upgrade decision, GNS Science decided to undertake additional monitoring of the volcano.
GNS Science issued an alert bulletin based on recent observations late today indicating that activity at the volcano has eased slightly.
The release by Steve Sherburn, the GeoHazards Duty Volcanologist stated that seismic activity at Ngauruhoe remains elevated, but has declined from the 50-odd volcanic earthquakes per day recorded earlier in June to 10 – 20 events per day.
The largest earthquakes are approximately magnitude 1, at a depth between 1 and 4 km, located slightly north-east of the summit.
At this early stage of the investigation, vulcanologists have been hampered by the small size of the earthquakes and equipment available to measure them.
Three additional seismographs have been installed around the base of the volcano, but only one of them can be regularly monitored – the other two will have their data uplifted at fortnightly intervals, weather permitting.
Other measurements made at the volcano have involved checking vent temperatures and analysing the gases being emitted. The data still needs to be studied, but early analysis of temperature data indicates that it is at April levels, and carbon dioxide levels (which could indicate the presence of magma) are at May 2003 levels.
Temperature and gas measurements will be taken at regular intervals, probably fortnightly.
At this stage, GNS Science has kept the alert status for the volcano at Level 1.