Mt Ruapehu Lahar

[Grant]

The torrent of water and mud which burst out of the hot crater lake atop Mt Ruapehu on the North Island's volcanic plateau today could have been far worse, say authorities.

A seven-metre high soft rock and ash dam that had penned the lake since the mountain erupted violently in 1995 finally gave way late this morning.
The escaping water gouged out rocks and earth and other debris carrying them down the mountain in the classic mudflow know as a lahar.
There were no reports of injuries.

Some officials said this afternoon they believed the 85 metres- wide dam, on the southeast summit of Ruapehu, had not collapsed entirely and that the water had pulsed out of the breach rather than in one giant explosive flow. That minimised any possible danger to life and property

Photos: Lahar could have been much worse - 18 Mar 2007 - NZ Herald: New Zealand National news

[Grant]

Couple of webcam images from during and after.



Horizons Regional Council

[Grant]

A small lahar occurred from Mt Ruapehu's Crater Lake this morning (approximately 1130hours) followed by a bigger, but moderate, second lahar (approximately 15-20 minutes later).

The Horizons Emergency Operations Centre was activated at 1138hours to monitor and support responding agencies.

The Whangaehu river level at the time of activation was 1.2 metres. It later peaked at approx 6.5 meters (recorded at the Railway Lahar Sensor Tower north of Tangiwai).

The lahar is expected to decrease in size as it travels further down the river.

A helicopter was deployed by Horizons to photograph the extent of the lahar and two survey teams have been sent to sample the lahar material.

“At this point, all has gone ahead as planned and I am pleased at the co-operation between the different agencies involved,” says Horizons chief executive and Group Controller, Michael McCartney

Horizons Regional Council

[Grant]

Sensors at the summit of Mt Ruapehu have recorded a series of small earthquakes since Sunday's spectacular lahar.

"The rapid removal of water from above a hydrothermal system can destabilise that system, resulting in small-scale eruptions," said Brad Scott, volcano surveillance co-ordinator at GNS Science, which maintains the sensor system.The quakes measured up to magnitude 1.

Lowered lake levels could lead to increased heating and steam-driven eruptions, Mr Scott said.

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[Grant]

Many thanks for Citizen Science Journalism » Ron Schott’s Geology Home Companion Blog whos linkback to NZ Weather pointed me towards New Zealand's source for National news video clips on Stuff.co.nz a raw video feed of the Lahar

[Kiwi]

amazing footage and clips.