Ruapehu run still on despite extra activity

Organisers of an adventure run on the slopes of Mt Ruapehu are meeting volcanologists amid fears it could erupt in coming weeks.

Signs of increased volcanic activity since last week prompted the central North Island mountain's Aviation Colour Code to be raised from green to yellow to reflect signs of elevated unrest.

The Goat, a 21km run from Whakapapa to Turoa Ski Fields across the western slopes of Mt Ruapehu is due to take place on December 1.

Organisers yesterday said the event was still planned to go ahead, but they have met volcano experts and would continue to monitor the situation.

Changes in measurements at the volcano over the past few weeks showed pressure was building and an eruption was more likely over "the next weeks to months", said GNS Science volcanologist Steven Sherburn.

"It's pretty much status quo at the moment and we're waiting on a good day to go up there and take some samples," said volcanologist Nico Fournier.

In particular, experts were for checking for increased earthquake activity, and changes in crater lake levels or the chemical composition of the lake, which were all potential signs of increased volcanic activity, he said.

Last week the temperature a few hundred metres beneath crater lake was about 800C, but the lake itself was only about 20C, suggesting a vent was partly blocked, which may be leading to a pressure build-up, Mr Sherburn said.

"A sudden release of the pressure may lead to an eruption."

Experts are monitoring activity at the volcano.

Small earthquakes have been occurring about 5km beneath the summit area of Ruapehu since late October, but these might not be directly related to the high temperatures beneath crater lake because they were much deeper, said GNS scientists.

The last eruption at Mt Ruapehu was in 2007.

A year earlier, an eruption also occurred and caused a small earthquake near the crater.