Pressure builds under Mt Ruapehu
- From: AAP
- November 16, 2012
PRESSURE is building under New Zealand's Mt Ruapehu and scientists are warning there is an increased chance it will erupt.
The aviation alert level around the central North Island has been raised to yellow - suggesting unrest above background levels - but the volcanic alert level remains unchanged at "signs of unrest".
GNS Science vulcanologist Steven Sherburn says the changes make scientists believe eruptions are more likely in the coming weeks to months.
"We are monitoring Ruapehu closely, but it often does not give any immediate warning that it is going to erupt," he said.
"We think that the temperature a few hundred metres beneath Crater Lake is about 800C, but the lake itself is only about 20C.
"This suggests the vent is partly blocked which may be leading to a pressure build-up beneath Crater Lake.
"A sudden release of the pressure may lead to an eruption."
Since late October small earthquakes have been recorded about five kilometres beneath Ruapehu's summit, but they may not be directly related to the high temperatures beneath Crater Lake.