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Increased likelihood of an eruption at Ruapehu - 16/11/2012

Recent measurements at Ruapehu indicate that the likelihood of an eruption has increased, GNS Science said today.

“We think the pressure beneath Ruapehu Crater Lake has increased and this makes an eruption more likely over the next weeks to months,” Duty Volcanologist Steve Sherburn said.

“We are monitoring Ruapehu closely, but it often does not give any immediate warning that it is going to erupt,” Dr Sherburn said.

The temperature beneath Crater Lake is about 800oC, but the lake itself only 20oC. This suggests the vent is partly blocked which may be leading to a pressure build-up beneath Crater Lake. This means there is a heightened likelihood of eruptions over the coming weeks to months.

Since late October small earthquakes have been occurring about 5km beneath the summit area of Ruapehu, but these may not be directly related to the high temperatures beneath Crater lake as they are much deeper. As a result of these observations, GNS Science has increased the Aviation Colour Code from Green to Yellow, reflecting elevated signs of unrest. However, the Volcanic Alert Level remains at 1.

Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community. Code Yellow indicates that a volcano is experiencing signs of elevated unrest above known background levels.

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 1 indicates a departure from typical background surface activity.

A build-up of pressure beneath Crater Lake is thought to have caused the 2007 eruption and a smaller eruption in 2006.

Brad Scott, Steven Sherburn. Phone 07-374-8211