This post will most likely be updated fairly quickly as news come up and we get more information.
It seems like Mt Tongariros awaited eruption has started. The eruption seems to be generated out of the Te Mari Craters. Witnesses report an ash column that exceeds 6 000 meters with steady lightning. There are also reports of lava bombs or incandescent lava slabs being ejected from the volcanic vent located on the side of the mountain. That witnesses talk about a hole in the side of the mountain points towards a new crater in the Te Mari crater-area.
Tongariro is a part of the Taupo volcanic belt. It is one of the most prolific volcanoes in New Zeeland. The last eruption was in 1977. During the last 115 years it has erupted 49 times through the southern crater complex, Ngauruhoe, while the Te Mari crater has been dormant. The Eruption follows magmatic emplacements during 2006 and 2009 and increased activity during the last few weeks.
The Ngauruhoe eruptions have been moderately explosive with only 3 eruptions ranging VEI-3; the others have been predominantly VEI-2 eruptions with just a few being even smaller. 550 BC there was the last larger eruption, a VEI-5 out of Ngauruhoe crater. The last VEI-5 out of Te Mari crater was 9350 BC.
There is currently nothing pointing towards this eruption going to exceed a VEI-3 eruption. One should though note that eruptions from previously semi-dormant craters in a complex andesitic volcano can be livelier than the previous eruptions from a well used crater part.
The amount of activity and height of initial ash column seems to point more towards a small VEI-3 than a VEI-2. So there is some cause for concern for those who live close by.
This post will be updated as soon as we get more news. For latest news we recommend that you follow the comment thread. Expect that there will be a call for evacuation of locals soon.
Update by Spica