The eruption of Ruapehu, June 1996.
Just like Mt Tongariro’s surprise bang on Wednesday afternoon, what happened a few kilometres away at 8.20pm on September 25, 2007, came suddenly and violently.
Shortly before airline pilots noticed a black plume rising above Mt Ruapehu, a volcanic blast threw ash, rocks and water across the summit area, sending two muddy torrents down the skifields.
Inside a hut on the edge of the crater lake, William Pike and James Christie heard a “massive boom” before the building’s door was blown from its hinges and mud and rock poured inside. Mr Pike’s crushed leg later had to be amputated.
The warning signs Mt Ruapehu gave in the days before that explosive moment are being seen again now – worrying scientists that the mountain could be about to produce a similar-sized eruption.
GNS volcanologist Michael Rosenberg said Mt Ruapehu has been showing two forms of unrest, which are considered unrelated.
There have been 45 earthquakes about 5km beneath the mountain since early August, but 35 of those have come in the past month.
[Read More – NZ-Herald]
The Te Maari crater at 1.30pm today. Photo / Geonet
Mount Tongariro has erupted, GNS Science reports.
The eruption came from Te Maari Crater, on the western side of the mountain, shortly before 1.30pm.
A massive plume of ash can be seen coming from the mountain.
GNS Science duty volcanologist Nico Fournier told APNZ the eruption happened about 1.20pm.
“There was one eruption, essentially one explosion, and it was not sustained. It spewed some ash possibly a couple of kilometres up the air. The ash is now drifting to the east-southeast.”
Dr Fournier said the eruption was not very loud and was smaller than an earlier eruption in August.
Tongariro, in the centre of the North Island, erupted in August for the first time in 115 years, sending ash as far east as Napier.
According to GeoNet, Tongariro is a complex of multiple volcanic cones constructed over a period of 275,000 years.
The mountain’s active vents include Te Maari, Emerald, North Crater and Red Crater.
Last week GNS Science increased the likelihood of neighbouring volcano Mt Ruapehu erupting, following increased activity on the mountain.
Read More – nzherald.co.nz
Scientists are warning there are heightened signs of volcanic activity at Mt Ruapehu and an eruption could be just weeks away.
GNS Science experts say pressure is building up in the crater lake at the volcano and there is now a high risk of an eruption.
Volcanologist Steven Sherburn 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.”
[Read More – NZ Herald]
The blackened crater of Mt Ruapehu after it erupted in 2007. Photo / John Cowpland
The likelihood of Mt Ruapehu erupting has increased, GNS Science says.
GNS Science duty volcanologist Steven Sherburn said changes in measurements at Ruapehu over the last few weeks indicate eruptions are “more likely over the next weeks to months”.
“We are monitoring Ruapehu closely, but it often does not give any immediate warning that it is going to erupt,” Dr Sherburn said.
“We think that the temperature a few hundred metres beneath Crater Lake is about 800 degrees Celsius, but the lake itself is only about 20 degrees Celsius. 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.”
As a result, the Aviation Colour Code has increased from Green to Yellow. However, the Volcanic Alert Level remains at 1. Code Yellow indicates a volcano is experiencing signs of elevated unrest above known background levels.
GNS said small earthquakes have been occurring about 5km beneath the summit area of Ruapehu since late-October, but these may not be directly related to the high temperatures beneath Crater Lake as the earthquakes are much deeper.
A build-up of pressure beneath Crater Lake is thought to have caused the 2007 eruption and a smaller eruption in 2006.
Source – nzherald.co.nz