Tongariro remains restless
The Te Maari crater on Mt Tongariro is still restless, but no further volcanic activity has occurred since it erupted for the first time in more than 100 years.
The eruption, on August 6, widened and deepened the crater, and reactivated vents which had been covered up in the 116 years since it last erupted in 1896, GNS volcanologist Brad Scott said.
Hot steam and adverse weather has prevented scientists from being able to get close to the crater to properly assess it, but they have recently been able to retrieve a GPS receiver, which was buried beneath 30 centimetres of ash and debris.
They are hoping the receiver will be able to provide data on last month's eruption.
The weeks leading up to the eruption were marked by a series of earthquakes in the area, but the Te Maari crater erupted with generally no warning on August 6, forcing people to evacuate their homes, and coated surrounding areas in ash.
Seismic activity has remained low in the six weeks since, but some small earthquakes have been recorded in the area.
Gas levels have fluctuated, but indicate that the volcano is in a continuing state of unrest, volcanologist Gill Jolly said.
Sulphur dioxide levels taken on September 13 and 18 were 980 and 540 tonnes per day respectively, compared to the 2100 tonnes recorded on August 9.
Gas composition, in general, has reverted back to concentrations similar to those recorded prior to the onset of unrest in mid July.
GNS scientists have re assessed the three possible scenarios for the next month.
The most likely scenario is that there would be no further eruptions, next most likely is that a similar eruption to the one last month would occur, and the scenario considered least likely is that a larger eruption would occur.
Any further eruptions could occur with little or no warning.