ONTAKE VOLCANO, JAPAN - 27 September eruption tragedy
Ontake is not a very "handsome" volcano - not a symmetric cone like Fuji, but it is the second-highest volcano in Japan, and is a sacred mountain, easy to climb, and tens of thousands of pilgrims and nature-lovers climb to its summit every year. The lower slopes of the volcano are marked by hot springs, and elegant ryokan (Japanese Inns) abound (I luxuriated in one of these back in 1988, when I studied a major lahar that was triggered by a M=6.8 earthquake under Ontake 20 years ago-killing about 20 people). Ontake has not had a major eruption in over 5,000 years, but has been characterized by violent phreatic (steam-blast) eruptions in 1979, 1991, and 2007. The 27 September, 2014 eruption appears to have been another phreatic eruption - caused by the de-pressurization of super-heated steam (an exploding geothermal system) beneath the summit. It appears that over 30 hikers have been killed by flying debris and choking ash - our hearts go out to the victims and their families.....
Phreatic eruptions are the most dangerous ones for volcanologists to deal with - because there is almost no precursory activity that can alert volcanologists of the threat. I have lost more of my friends to such eruptions (Karkar, 1979; Galeras, 1993) than to any other type.
Error Report - my apologies:
Rick Hazlett and I have a photo of Ontake Volcano in our VOLCANOES - Global Perspectives book (Figure 11.1, p. 343) - but unfortunately Ontake was mislabled as Unzen! We even let this error slip past in the most recent (2014) reprinting - AUWE!!!!!
I spent over a month working in Indonesia two years ago, attended this month's Cities on Volcanoes meeting in Jogjakarta, and was again impressed with the country's beauty and variety of its volcanoes, and by the capabilities of its hard-working volcanologists. Indonesia has over 100 "active" volcanoes (those that have erupted in historical time and have the potential to erupt again), and typically 6-10 of them erupt each year! Two of them (SINABUNG and KELUT) have been in the news lately and are worth describing.
[Late September, 2014] Sinabung continues to erupt...here's some background
SINABUNG is an isolated, small stratovolcano located near the gigantic Toba caldera - site of one of the world's most powerful "super eruptions" 75,000 years ago (VOLCANOES-Global Perspectives, p. 259). This area is relatively sparsely populated, although nonetheless about 30,000 people have been evacuated from surrounding villages since Sinabung's current eruption began in 2010. 17 people have been killed so far by pyroclastic flows from this eruption - mostly because they returned too soon to their evacuated homes. Eruptions are rare on Sumatra, and it is interesting to speculate if this eruption is in some way related to the tectonic forces that caused the great Sumatra earthquake in 2004?
KELUT (or Kelud), in densely populated eastern Java, is one of Indonesia's most deadly volcanoes, and eruptions have killed more than 3,000 people in its 1,000 year recorded history - mostly by lahars that resulted from eruptions that ejected mud and ash from a central crater lake. That lake was displaced by a growing lava dome in 2007, and the volcano had remained quiet until 13 February of this year, when increasing seismic activity prompted the Volcanological Survey of Indonesia to issue a Stage IV Alert and to begin the evacuation of people in the danger zone. Eventually more than 100,000 people were evacuated, but to the credit of VSI, only 5 lives have been lost. Ash rose to 17 km above Kelut, and about 50 million m^
3 of volcanic ash was erupted. The explosive phases of this eruption were short-lived, the Alert level has been lowered to Level 2 (warning), and people are being allowed to return to their ash-buried homes and rice fields.