Mt Ruapehu continues to show signs of unrest with high levels of volcanic gas emissions and crater lake temperature increases.
The volcanic alert level of Mt Ruapehu remains at 2 and the aviation colour code at yellow.
Eruptions are much more likely at volcanic alert level 2 in comparison with volcanic alert level 1.
On Wednesday morning, GNS duty volcanologist Brad Scott reported the crater lake – Te Wai ā-moe – had risen to 41C and steam plumes could be seen.
Observation flights last week confirmed these steam plumes were not caused by an eruption. They were related to a combination of increased heat flow at the crater lake and still, cold atmospheric conditions.
Over the past 12 days, the crater lake temperature has peaked at 41C following a four-week period with temperatures between 36C and 38C.
Since early March, GNS has been recording strong volcanic tremors at Mt Ruapehu. It has been the most sustained and vigorous set of volcanic tremors recorded in two decades.
And although tremor levels remain high, there has been a decline in tremors this past week.
Due to the heightened volcanic unrest, GNS Science staff are carrying out more frequent aerial observations, gas measurements and crater lake sampling.
A gas measurement flight on May 4 confirmed high sulphur dioxide and carbon dioxide fluxes, respectively of 260 and 1970 tonnes per day of gas.
Further monitoring flights will be conducted when weather conditions are suitable.
This period of unrest of Mt Ruapehu could see minor eruptive activity that is confined to the lake basin or no eruptions. This level of activity may generate lahars in the Whangaehu River.
Another scenario is a larger eruption that impacts the summit plateau with volcanic surges and generates lahars in multiple catchments, like what was seen after the September 2007 eruption, or older events like those in 1975 and 1969.
The chance of a prolonged eruptive episode or a larger eruption, such as occurred in 1995-96 with wider ashfall impacts, is higher than it was two months ago but remains very unlikely within the next 4 weeks.
Credit: Stuff.co.nz
