Vulcanologists trying to predict Tongariro's next move have been driving up and down State Highway 46 collecting samples of gas coming from its crater.
According to GNS vulcanologist Gill Jolly, it has been a difficult task over the last few weeks because of northerly winds and cloudy conditions.
The scientists are using the intensive testing regime to try and forecast Tongariro and Ruapehu's behaviour after Tongariro blew on November 21.
"The gases were relatively low - similar to some of the measurements we've done over the last couple of months, which were not as high as immediately after the eruption on August 6," Jolly said.
"There's still gas coming out, but not in the really high concentrations."
As well as gathering collect from the ground, GNS has flown around the crater to collect gas.
She said GNS was not seeing any signs volcanic activity would become more vigorous.
Meanwhile, scientists await final results of a comprehensive test of Ruapehu's crater lake.
The volcano has thrown up stable results over the last fortnight, but scientists were still on high alert after Tongariro's unexpected eruption last month.
Jolly said the test taken on Ruapehu last week, which would give insight into what was going on in the crater, was due any day now.
"We're still looking at the temperature of the crater lake and that's pretty stable," she said.
"The seismicity has been pretty low for the last wee while, so it's relatively quiet, but we still have that uncertainty about what's happening underneath the vent. So we're still on a high level of alert."
The test involved flying a helicopter to the crater lake, taking a water sample, and analysing the gases that have dissolved in it.
"Those gases can tell us about what's happening in the vent area around 600m down,"Jolly said.
"They usually happen once a month, but they're doing them more frequently, around every couple of weeks."
She said the exercise of getting a helicopter up to the crater and going through the data was expensive and time-consuming.
- © Fairfax NZ News
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