This is the scientific discipline behind Mount Ontake ’s crimson eruption in Japan on Saturday morn . Unbelievably , many hikers outlive , documenting their perspective of the pyroclastic flow and trekking out of the volcanic wasteland .
Left : Hikers empty after the extravasation . Credit:@mori____mori . justly : Aerial eyeshot of the Mount Ontake eruption . Credit : NHK
The clap occurred mid - morning on a beautiful Saturday , when tramper were out on the volcano enjoying the start to their weekend . injury were report in the immediate aftermath , withpeople lose at near a shrineandpotentially elsewhere , and potential fatalities in the hours ahead . This is one of those times where I palpate dead lost as a catastrophe scientist : I can excuse what happened and why , but that does n’t help any of the people who are going to be grieving lost have it away ones before today is over .
The vent is a popular goal forreligious pilgrimages , and many hikers were out delight the beautiful get-go to the weekend and the autumn hiking season when the eructation hit . This photograph ofNinoike , apondjust short of the volcano ’s summit , was posted shortly before the volcanic eruption :
https://twitter.com/embed/status/515695458128101376
Twitter user enari had n’t send any message since the eruption . While I optimistically trust survived in the pond - side hut , were posting a picture long after their trip to the summit , or otherwise this - isn’t - what - it - aspect - like , I ’m not feel affirmative . ( Update : Asimilarly - discover account claiming to be the enarisaysthey’re fine , lost their phone in the chaos so had to make a new account , and that thephoto is from 30 min prior to the eruption . I have no way toverify this claim . ) ( Update : The original account post a billet saying she was fine and blue-pencil the accounting . The second news report come along to be a fake . Thank you to a lovely collection of folks for expire along the inter-group communication . )
The eruption start at 11:53 am Saturday local time . Alive webcaminstalled at Takigoshi captureda pyroclastic flow chasing down the south face of the volcano . Japan Broadcasting Corporation NHK releasedaerial TV of the clap available here , another picture include hoi polloi on a ridgeline with the glowering ash towboat , and adifferent vantage distributor point before aerial footage here :
Geoscience of the Ontake Eruption
Japan is at a triple - plate subduction boundary between the Eurasian continental plate and the Philippine and Pacific pelagic plates .
As the denser oceanic plates plunk below the scummy - concentration continental home , piss from the saturated sediments lour the melting point in time of surrounding rock . That magma feeds a range of volcanoes mirroring the plate boundary .
Plate tectonic diagram . Image credit : Volcano World
Volcanoes can develop gentle , burbling eruptions like those inHawaii , or landscape - scarring nightmares likeMount Saint Helens , Krakatoa , Vesuvius , and Mount Pinatubo . The skill of predictingwhich vent will produce what character of outbreak is in their geochemistry . volcano with silica - plenteous lavas yap gas pedal , break out violently . vent with silica - wretched lavas allow the throttle to hightail it , erupting gently . Whiledetails and exclusion can get complicated , the general rule of quarter round is that volcanoes over pelagic tectonic plates are gentle , and volcano along pelagic - continental boundaries are violent .
Along the tectonic boundary in Japan , the thaw magma from the subducting pelagic home plate get down out silica poor . But , as it rises through the continental impudence , it picks up silica . By the time it erupts , the is classified as an intermediate lava , with a high silica that produces spectacularly violent eruptions . These eruptions shape the very landscape of Japan with iconic conic stratovolcanoes like Mount Fuji and Mount Ontake .
The geochemistry of stratovolcanoes immediately drives all other characteristics about them . Thick , high - viscousness lava flows bring forth exorbitant , conical vent compared to the gently rounded shield volcanoes made by fluid low - silica lava . Silica - ample magma produces lightsome - colourize stone , slowly crystalize into pinkish and grey granite with peck of lechatelierite and feldspar alternatively of dark basalt and gabbros . But the most sorely patent difference is in the vehement , hazardous eruptions grow but silica - copious lava .
entrap gasoline in silica - rich lava drive volatile eruptions with predominate cloud of abrasive ash and passing speedy pyroclastic flows .
It even producesvolcanic bombs , clod of lava eject from the crater to land as aerodynamic missiles anywhere within kilometer of the bang .
Volcanic dud at Craters of the Moon National Park in Idaho . Image credit : National Park Service
Heavy , toxicant gasesseep out of the rock-and-roll , sinking into depressions and valley to taciturnly and invisibly put out anyone nearby . The eruption can be magnify by lahars : washy , speedy landslide . encourage by quickly melting snow , lahars are exceedingly destructive , washing away and bury anything unlucky enough to be downstream . Eruptions can also trigger more mundane landslide with earth tremor , emptying magma chambers , and redistribute of tenseness destabilizing slope .
This horrible collection of hazards including pyroclastic flows , ash tree , and pyroclastic dud is exactly what is pass off at Mount Ontake .
First-Hand Accounts of the Eruption
Unbelievably , some hikers in the region not only witnessed the irruption and survived , but recorded it .
Pyroclastic flows frighten me . Everything about them is terrorise : they ’re implausibly fast superheated volcanic flows with billowing clouds of poisonous gas that can travel mindbogglingly long length at outrageous velocity . My only selection advice if you see one coming towards you is , “ Be somewhere else . ” These people are so , so lucky to be live .
Several hikers grapple to take resort in a army hut . Twitter exploiter Mori Shota was hiking near the volcano at the clock time of the eruption . They describe the clap as sudden darkness , the extravasation blocking all light to leave them in delivery darkness . They share the following series of picture while sheltering in a army hut with other hikers :
https://twitter.com/embed/status/515701211769491456
https://twitter.com/embed/status/515701349141340161
https://twitter.com/embed/status/515706795797381121
Hikers sheltered within the hovel during the eruption :
https://twitter.com/embed/status/515740629595209729
Some of the survivor hiked out with ash still rain down down on them .
https://twitter.com/embed/status/515726159368044545
The heat of magma rising within the vent melted Earth’s surface blow , adding to existing weewee overflow . Ash is so thick that local streams are opaque , running white with suspend sediment :
https://twitter.com/embed/status/515746402110955520
Once reaching the roads , they were collect by pinch responders and bused out of the region :
https://twitter.com/embed/status/515758459032072193
Another Twitter user , あべるん , had a similar experience . Their photo of a construction near the volcano realize it open how ash from eruption can rapidly clog social system and cause roof crack up . Upon evacuate the realm , they returned to their car to come up it surface in ash :
9合目避難小屋から9合目石室山荘小屋まで退避雲と空と岩の世界が火山灰の死の大地に … #噴火#御嶽山pic.twitter.com / DRa2onaXZO
— あべるん ( @avel_yasuda)September 27 , 2014
えー、無事に下山致しました。応援、心配のリプを頂いた皆様、失礼だとは思いますがこのツイートにて下山報告とさせていただきます。本当にありがとうございました！#御嶽山#噴火pic.twitter.com / mVGwwbpEba
Still others in the neighborhood report thestench of sulfuraccompanied the eruption . The nearest hamlet is 12 kilometre from the summit , and isreporting no material damage .
Over 200 survivors have made it down the mountain;Prime Minister Shinzo Abe regulate the military machine to run search and rescue operation . Eighty help climberswent up the volcano to assist upward of 30 survivors who are seriously wound , inter , or otherwise unable to come down on their own . Not all were capable to be rescued before crepuscule , and with the volcanic eruption ongoing , will likelycontinue shelter in place within tourist villas overnight . law have set upa hotline for information on potential climbersthat may have been unaccounted for thus far .
Ashfall in the Surrounding Region
The ashfall is being observed by people far aside from the eruption in a rain of lilliputian , sharp shards of volcanic glass . The owner of a mountain lodgenear the volcano ’s summit is report half a beat of ashso far . In major eruptions with substantial ash tree output , the ash can overcharge structure , collapsing roofs .
https://twitter.com/embed/status/515700026069118976
Fine volcanic ash is extremely scratchy . The jagged nature of the drinking glass sherd is readily plain under blowup .
amplify view of volcanic ash produced by Yellowstone eruptions . double quotation : USGS
Theairspace around the volcano has been mark off - limits to aircraft . Apair of Jetstar flights diverted to an alternate airportto avoid potential ash .
Projected ash swarm . Image deferred payment : Japanese Meteorological Agency
Althoughflight rules involving ash tree cloudshave change since theinfamous Icelandic outbreak disrupted European flights , pilot still need to avoid ash to avoid splash delicate engine with molten glassful .
One Twitter user spy the eruption from their flying :
https://twitter.com/embed/status/515793739223023616
Ash can also lead to an increment in landslide risk of infection . The ash forms a slick layer of deposit prostrate to landslide in the future . It can also smother plant , kill steady flora .
Eruption History of Mount Ontake
Mount Ontakeis site between Nagano and Gifu prefectures in central Japan . At 3,067 meter magniloquent , the is the 2d tallest vent in the country 2d only to Mount Fuji . Mount Ontake is also known asOntakesan and Kiso - ontake . Despite the similar name , it is not related to Ontake , an offshore volcano with a vigorous extravasation history .
Area map of the centrally - located Mount Ontake volcano . range credit : Japan Meteorological Agency
The vent wasnot under any alerts or warningsat the clock time of the irruption , althoughit was in a period of heightened seismic activity(animation;seismograms ) . It seems like the volcano fail to present clear signs of an imminent eruption , but there could have beena breakdown in the monitoring summons . Even if monitoring was ideal , being close to a known alive vent is speculative with a whole mickle of potential peril .
Mount Ontake ’s last major blast was amajor series of eruptions stretch from October 1979 to April 1980 . The vent had not erupted prior to that in late history . Earlier claims that the vent erupted in 1892 or 774AD didnot stand up to review of the diachronic records .
1979 eruption at Mount Ontake . Image credit entry : Tokiko Tiba / National Science Museum
Although Mount Ontake has n’t had a volcanic eruption since 1979,it had a minor phreatic outbreak in 2007 , and anunconfirmed similar eruption in 1991 . Phreatic eruptions are steam - driven explosions triggered by magma heating plant groundwater . Many news show agency are cover this as the most late eruption .
Local university professorKoshun Yamaoka surmise the pyroclastic flow are low temperature , revelatory ofa hydrovolcanic eruption , where fundamental interaction between lava or magma and groundwater result insteam enhance the eruption ’s volatile potential . Volcanologist Shigeo Aramaki concurs , suggesting that the white cloud are characteristic of water supply steam . However , until he can collect and analyze ash tree samples , Aramaki is not ruling out the possibility of a more troublesome lava eruption .
I ’m not yet win over this is a phreatic eruption . Without access code to samples for analysis , the long - distance geogossip is that these eruptions lookhot , wakeful , anddecidedly not crocked . Gettingmassive pyroclastic fall out of phreatic eruptions is strange , but not impossible . We are n’t seeing lava in any of the footage or photographs so we also ca n’t find out that it ’s phreatic . Either way , it ’ll be interesting to see which style the evidence direct in the future . ( Update : Here ’s more onwhat phreatic bang are , and how they can happen without admonish . )
The volcano also had a major landslip failed in 1984 , sending a rubble avalanche tumbling 13 kilometers along river valleys andkilling 29 masses . The landslide seem to be set off by an earthquake self-governing of volcanic activity , although ash mixed in the deposit in all likelihood increase the landslide ’s mobility .
火山灰まじりの小雨降り始めたし、なんか混雑してきそうだから野次馬したい気持ちを抑えて速攻で下山してきました。写真貼らないとツイート出来ないので同じ写真貼りますpic.twitter.com / hAx9CcEdzh
— はせ ( @hase2019)September 27 , 2014
TheJapanese Meteorological Agency has since place the volcano under a Level 3 alert , warning everyone to stay out . A handwritten house at the entry to the vent warns people to stick away , read , “ The volcano has burst . Climbing taboo . ” ( Thank you forthe translation , Keshav Kini ! )
As always , I ’ll be fighting in the treatment department to help with your questions .
Errata : An early version of this article featuredimages from the Sakurajima eruption(thank you to@Cristoforoufor the correction ! ) , andrecycled a architectonic map from Chris Rowanwith a potentially perplexing epicenter marker from the 2011 Tohoku seism and tsunami . Thank you to@holasmithafor rendering assistance when the auto - translating robots failed me .
Update : Here ’s a follow - up on things we learned from this clap .
https://gizmodo.com/learning-from-mount-ontake-how-to-survive-an-eruption-1641993110
eruptionJapan
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