Volcanic Alert Bulletin TON-2012/28 - Tongariro Volcano
[link to info.geonet.org.nz
21 November 2012, 5:30 pm - Eruption update: activity decreased; Volcanic Alert Level is at Level 2; Aviation Colour Code changed to Orange
This afternoon’s small eruption at Upper Te Maari Crater appears to be over for now, GNS Science said today.
GNS Science has now decreased the Aviation Colour Code from Red to Orange signalling that ash is no longer being erupted. However, minor eruptive activity continues and the Volcanic Alert Level remains at 2.
The eruption occurred from the Upper Te Maari crater, in the same area that erupted on 6 August this year. Today’s eruption happened at 1:25 pm and lasted for less than 5 minutes although local earthquake activity continued for about 15 minutes. The eruption appears to have ceased for now.
GNS Science staff Nico Fournier, Agnes Mazot and Craig Miller witnessed the eruption from a few kilometres away. “We didn’t hear anything but could suddenly see an ominous dark grey cloud of ash drifting towards us” said Dr Fournier. The eruption was also seen by trampers walking on the Tongariro Crossing. There are no reports of injury.
Ash erupted during the first few minutes reached 3 km to 4 km height and was clearly seen from Taupo. A light dusting of ash fell across part of State Highway 46 and north-east towards Turangi but no more ash has been reported this afternoon as the gas and steam cloud drifts towards the south east. Ash is being collected this afternoon and will be analysed at Massey University to assess potential human and animal health effects. Results are expected in the next few days.
Today’s eruption did not produce any directed rock blasts or debris flows like those made by the August eruption.
This afternoon’s eruption occurred without any measured precursory changes and this reinforces the unpredictable nature of volcanoes. We cannot say what will happen next at Tongariro but the scenario considered most likely, based on the August 2012 eruption and the description of late 1890s eruptions, is that we could expect another eruption of similar size at any time during the next few weeks. Eruptions are not expected to escalate in size. Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community. Code Orange indicates that a volcanic eruption is underway but with little or no ash being produced.
The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 2 indicates that a minor eruption has occurred.
Brad Scott, Nico Fournier