Ash on the slopes of Tongariro from the August 6, 2012 explosion. Image courtesy of GNS Science and OneNews. The first eruption at Tongariro in 115 years decided to occur in the middle of the night, but as day broke in New Zealand, we have new details of the eruption from the Te Mari crater. GNS Science released multiple reports on the events of the night of August 6, 2012 - along with a highly informative and easy to understand press conference. In brief, here is what we know about the eruption:
A brief explosion occurred at 11:52 PM (NZ time)
There were little-to-no precursory activity beyond the increase in seismicity during the weeks before. However, nothing indicated an eruption would occur so quickly (such as volcanic tremor).
15-20 minutes of strong seismic activity followed the eruption
The eruption itself likely only lasted a few minutes.
There are no indications of new explosions are occurring at the Te Mari crater, but direct observations aren't possible due to cloud cover.
Ash samples from the eruption have been collected, so hopefully we will find out soon whether the material was merely accidental (old rocks blasted out by an explosion) or juvenile (new magma). GNS Science has said they think the eruption was a hydrothermal explosion, which makes sense with the idea that the eruption was very short and discrete. However, it sounds like ash spread pretty widely (see above) and blocks may have been thrown upwards of 1 km. It is unclear where this activity might lead - it could be a one-off hydrothermal explosion or it could be a precursor for more activity. This depends on whether magma is ascending under the crater - new magma means that more eruptions could occur. In either case, GNS Science is suggesting explosions like this might continue to occur for days, depositing ash close to the volcano. The New Zealand Herald posted a timelapse from a webcam pointed towards Tongariro showing the brief explosion that occurred late Monday night.
The plume from the August 6, 2012 explosion from Tongariro seen from the Suomi/NPP. Image courtesy of NASA, NOAA and CIMSS. Beyond the road closures around Tongariro, including the Desert Road stretch of Highway 1 and parts of Highway 46, a number of flights were cancelled around the North Island of New Zealand, especially from Hawkes Bay. We also have some good eyewitness description of the eruption along with pictures of the plume from the volcano when the weather allowed images as well. The Suomi NPP captured an image of the plume at night from space as well (see above) spreading off to the east. The New Zealand Herald has been adding new information throughout the day, including news that the Tongariro Crossing trail is still closed but the ski areas on Ruapehu are still open for business. I'll have more updates tomorrow as we get more news from New Zealand and I'll try to find some details about the eruption at White Island as well. UPDATE 8/7 9:00 AM: A few new pieces of information on the eruption and the response:
Locals living near the volcano think the government action was too slow in warning residents about the eruption and ash hazards.
The hiking hut nearest to the Te Mari Crater was damaged by debris, including boulders that reached a meter in diameter - and that hut is over a kilometer from the vent.
Here is some more details on what the cause of the eruption may have been - right now, there are also no indications that a larger eruption is going to occur.
OneNews posted a timeline of the events before/during/after the eruption.
The NZ Herald posted a somewhat informative and somewhat bizarre article on the threat of volcanic ash.
As with any major geologic event (at least in terms of media attention), there are the snake oil merchants trying to make spurious claims. The most appalling I've seen is the nonsense that Ken Ring is spewing about "predicting" the eruption using space weather - I'll repeat it folks: this IS NOT possible. He claims a "large eclipse" in November means more eruptions for "months" before and after. When your "predictor" is the size of 747, then yes, you can make yourself look good, but it holds no water whatsoever.
{Special thanks to all Eruptions readers who provided links for this post.}
