This weekend (September 27 Japan time), Mt Ontake (Japan’s second highest active volcanic peak at 3,067m or 10,062ft) suddenly erupted (phreatic eruption) at around 11:52 in the morning. The mountain is located at the border of Gifu and Nagano Prefectures.
Like Mt Fuji (the tallest active volcano in Japan), it’s a popular tourist attraction and many residents and tourists alike, make a trek up to the summit during the hiking season. One of the highest peaks (Kengamine) has lodging/hut facilities for hikers. There are other huts throughout the mountain peak. The following is a hiking video (fairly long at 7 hours) but it shows why people hike it; the scenery along the way and up at the top is incredible.
The pond/lake (there are five crater lakes) seen in the above thumbnail of the video is located to the north of the main eruption point which occurred on the southern flank of the volcano below the actual main summit crater. The following shows where everything is in relation to the eruption site.
Lodges at Kengamine peak
The following video was shot by a hiker as the eruption occurred. They were fortunate because that ash cloud was not a pyroclastic flow (superheated gas, ash, and rock). Scientists are still examining the data to see if there were any pyroclastic flows.
The later half of the following (around the 1m mark) shows what looks like a pyroclastic flow heading down the mountain.
And the following was taken near the summit of the main crater where the visitor lodges/huts are. While the main eruption occurred on the flank, the ash cloud and debris turned the summit pitch black. Many hikers crammed into the lodges for shelter (video shows how pitch black it was). Later reports said some roofs eventually caved in from the weight of the ash.
The following shows how much ash is sitting on top of the roofs.
The eruption has created a challenging/dangerous situation for rescuers as well as victims. They were able to evacuate the able bodied people out of the area but those with serious injuries, needed to be carried further down the slope and airlifted out via helicopter. But further search and rescue (of the unaccounted) as well as recovery of those known dead (36 known at this point) has proven to be difficult.
News reports said that first responders saw unconscious bodies near the eruption site and were presumed dead. Operations had to stand down on Tuesday (Japan local time) due to signs of increased volcanic activity as well as increasing levels of toxic gas.
While news reports said the mountain erupted without warning, there have been conflicting reports (this will get ironed out in the coming weeks). Some reports said that scientists with the Japan Meteorological Agency did notice a swarm of seismic activity back around September 11th and sent that information to local officials as well as the lodges at the summit. The local government however seems to have deemed it a non-threat though by not declaring the mountain off limits.
The following video was taken at the summit on September 22nd and shows a fumarole with some minor venting (the actual video was uploaded after it became known that an eruption occurred).
But the following video (which the user wrote was recorded on September 15th), was uploaded to YouTube on September 20th (21st in Japan) and shows a closeup of that same venting. While these fumaroles have been venting on the mountain for many years, this one is in the same general area where the eruption occurred.
I know, anyone who has been to Owakudani in Hakone, has seen these kind of vents. The Hakone area is seismically active as well but more like in the Yellowstone Park sense. This same kind of venting is seen at Kilauea crater (though Hawaiian volcanoes are the shield variety and do not have the same sort of violent ash eruptions as most volcanic peaks in Japan, Kilauea crater has had some explosive phreatic eruptions due to steam explosions from rain water). Ontake though is an actual active stratovolcanic (the most dangerous type) peak which last erupted in 1979.
So I’m just curious if that rumor was just a rumor or if there really was a small amount of seismic activity that would’ve warranted shortening the hiking season on the mountain.
