Mount Ruapehu has experienced some of the strongest tremors GeoNet volcanologists have seen in the last eight years.

The tremor activity has been seen in the last two-three weeks and volcanologist Art Jolly says signals are similar to those in 2006 and 2007 but weaker than those recorded in 1994/1995.

Ruapehu last erupted in 2007 when a hydrothermal eruption smashed into the Dome Hut injuring a primary teacher when a rock fell on him, and sending two lahars down the mountain.

The spectacular eruption in September 1995 created ash clouds that disrupted air travel, occasionally closing airports and the central North Island airspace. Ash from that eruption fell in Tauranga and Mount Maunganui.

Episodic eruptions continued until the end of November 1995.

'Historically we have not seen a direct relationship between volcanic tremor and discrete volcanic eruptions or sequences of eruptions,” says Art. 'However it is one of those signals often present before, during or after enhanced volcanic unrest.”

The Crater Lake remains in a heating phase which started in late 2014 when the lake was 15°C, reaching a peak of over 40°C in late January–early February 2015. The temperature declined to about 31°C in mid-March and is now at 37-39°C.

No other changes at the Crater Lake have been observed.

Mt Ruapehu remains at Volcanic Alert Level 1 (minor unrest). The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.

The Aviation Colour Code is Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

GNS Science continues to closely monitor Ruapehu through the GeoNet project.