Mount Fuji (Fujisan)

Mount Fuji 



Mount Fuji, an iconic stratovolocano and Japan’s highest mountain 3,776.24 m (12,389 ft), is 100 km south west of Tokyo (and is also one of the few volcanoes I have actually visited -but not climbed!).  She is a cultural heritage site.  According to UNESCO and Wikipedia, “Mount Fuji has “inspired artists and poets and been the object of pilgrimage for centuries”. The site includes the volcano itself, Fujisan Hongu Sengen Taisha and six other Sengen shrines, two lodging houses, Lake Yamanaka, Lake Kawaguchi, the eight Oshino Hakkai hot springs, two lava tree molds, the remains of the Fuji-kō cult in the Hitoana cave, Shiraito Falls, and Miho no Matsubara pine tree grove” [1,2].

Fig 1 Mountfujijapan

Fig 1: Mount Fuji with cherry blossom and Shinkansen (high speed train) by Swollib published under Wiki Commons. Source:

Mount Fuji formed on the foundation of an old quaternary volcano, Komitake, in four phases: the first phase, Sen-komitake, an andesite core was recently discovered deep within the volcano; the second, “Komitake Fuji,” a basalt layer believed to be formed several hundred thousand years ago; the third, about 100,000 years ago, “Old Fuji”, formed over the top of Komitake Fuji; and, fourth and lastly, “New Fuji” formed over the top of Old Fuji [1].
New Fuji, the current stratovolcano, formed 11,000 to 8,000 years BP with effusive lava flows followed by a three and a half thousand year period of minor explosive eruptions and then major lava flows from 4,500 to 3,000 BP. Later eruptions have been intermittent major eruptions with smaller lava flows and small pyroclastic flows. The Fuji Five Lakes were formed when basaltic lava flows blocked drainage from the Miska Mountains [3].

Current Status
Mount Fuji is active. GVP lists 67 eruptions, of which three are VEI 5, two are VEI 4, five are VEI 3, 19 are VEI2, one is VEI 1 and the remaining 37 have no VEI number. The last eruption was in 1707 and a VEI 5 which formed a new crater and also deposited ash on Edo, Tokyo [3].
Following the 2011 Tōhoku 9.0 Mw earthquake and tsunami [4] and a 6.2 on 15 March 2011 a few kilometers to the south of Mount Fuji, Mount Fuji was studied in depth to assess the risk of eruption. It was concluded that an eruption was not likely. At the time of writing in May 2014, there is no alert for Mount Fuji.

Tectonic Setting
Mount Fuji’s tectonic setting is classified as continental subduction zone. Plotting the latest 5,000 earthquakes (August 2010 to May 2014) reported by IRIS [8] we can see that the subduction of the Pacific Plate under the Okhotsk Plate dominates seismic activity in the area:


Fig 2:  Plot of the earthquakes showing Depth v Longitude by the author.  Colour denotes depth. Reproduced with kind permission from the author.

Fig 2: Plot of the earthquakes showing Depth v Longitude by the author. Colour denotes depth. Reproduced with kind permission from the author.

Fig 3: Plot of the earthquakes showing Latitude v Longitude by the author, superimposed over a view of the same area from Google Earth. Reproduced with kind permission of the author.

Fig 3: Plot of the earthquakes showing Latitude v Longitude by the author, superimposed over a view of the same area from Google Earth. Reproduced with kind permission of the author.

While being located in a volcanic archipelago, her lavas are: Basalt / Picro-Basalt; and, Andesite / Basaltic Andesite, Dacite [2]. That her major lava type is Basalt / Picro-Basalt, which is similar to those of mid ocean ridges, implies that her lava generation is more complex than straightforward subduction.
Mount Fuji is located at the triple junction of the Amurian Plate, the Okhotsk Plate, and the Philippine Sea Plate. The relative motions of the plates may provide a mechanism to enable large eruptions of basalt.

Fig 4: Map of tectonic plates from a detailed map showing the tectonic plates with their movement vectors near the Philippines published under Wiki Common.  Source:

Fig 4: Map of tectonic plates from a detailed map showing the tectonic plates with their movement vectors near the Philippines published under Wiki Common. Source:

K Aizawa et al [5] carried out a wide-band magnetotelluric study on the Mt. Fuji area in 2002 and 2003.  They propose that Mount Fuji’s magma chamber is located at a split in the subducting Philippine Sea Plate.  Collision of the Izu block with the Honshu block about two million years ago may have caused the split in the Philippine Sea Plate.  The resulting tensile stress field in the lower and middle crust beneath Mt. Fuji would allow mantle-derived basaltic magma to ascend easily, similar to the rise of basaltic magma at mid-ocean ridges.

The 1707 eruption
This eruption started after an 8.4 earthquake (the big earthquake) on 28 October 1707 in south west Japan which devastated Honshu Island, followed by smaller earthquakes in December 1707 near Mount Fuji itself. According to Volcano Discovery [6]: the eruptions started on 16 December 1707 with the creation of the new crater and a sub-plinian column of ash and pumice, turning into basaltic lava fountaining six hours after the onset of the eruption. The total volume of lava erupted over 16 days was estimated to 0.68 cubic km. Violent explosions were recorded until 25-27 December, before eruptive activity dropped, ending on 1st January 1708. Tsuya, H [7] gives a more detailed account of the eruption itself, which I recommend.
Is it possible that the plate movement associated with the big earthquake of 1707 resulted in a tear in the crust which permitted the rapid ascent of magma? Whether or not the big earthquake was sufficient or whether there had been other earthquakes (not reported) is an open question.
And lastly, a brief reminder that there is no alert for Mount Fuji at the moment. Current alerts for Japanese volcanoes can be found here:
Hope you enjoyed reading this. The usual caveats apply: “Not an expert, etc ….”

KarenZ, 15 May 2014

1. Wikipedia:
3. GVP:
4. Wikipedia:
5. Aizawa, K., R. Yoshimura, and N. Oshiman (2004), “Splitting of the Philippine Sea Plate and a magma chamber beneath Mt. Fuji”, Geophys. Res. Lett., 31, L09603, doi:10.1029/ 2004GL019477.
7. Tsuya, H “Geological and Petrological Studies of Volcano, Fuji, V.: 5 On the 1707 eruption of Volcano Fuji.”, Bulletin of Tokyo University Earthquake Research Institute. 33 books (3), 1955.12.10, pp. 341-383.
8. Earthquake data from IRIS:
9. Japan Meteorological Agency:


Friday riddles: 

1. Bane of the Rattlesnake; It’s on the wrong track!

2. In a field of one-hit-wonders, I stand alone.

3. Special sheep and loony toons?


69 thoughts on “Mount Fuji (Fujisan)

  1. What lovely, informative posts, Chryphia and Karen Z! Such an interesting read for a busy afternoon! I will come back for more.
    Now I am looking suspiciously at Hekla’s last moves – are they of any significance?
    Thank you girls!

  2. Interesting because I was having thoughts yesterday that nothing on Japanese Volcanoes had been published in awhile. Mount Fuji is another one of those volcanoes that has multiple facets from which magma can arise into it’s reservoir? Scary to think mostly magnitude 5 eruptions occur at this location, It is a good thing that she is at peace with herself.

      • It’s had 3 VEI-5’s in the last 3500 years. I think it’ll be a while before we see another large eruption at Fuji given the average repose time, but that’s difficult to say with any type of certainty.

        I think what would potentially be worrisome at Fuji is edifice instability, especially considering the fact that the last eruption was a large scale flank eruption.

  3. Fuji gets a lot of press and publicity, and as most people know, is very well-studied. With that said, I think it merits lots of discussion since it’s a unique and fairly interesting volcano. Great post!

    Another interesting volcano that gets little discussion is Fuji’s neighbor Hakone ( I feel like in some ways, Fuji is the Vesuvius to Hakone’s Campi Flegrei.

  4. Interesting. Fuji’s chamber is in a split in the Philippine plate? That’s a spooky thought. Tectonic forces could force that split to change in over all volume and create massive over pressurization then.

    Also, If I remember, this is also the region that has a plate shard wedged up underneath the the crust and over the subducting plate.

    With all that going on, Fuji has got to be one tough nut to crack.

  5. Thank you for a great read on Mt Fuji. Just a couple of days ago I was wondering what news was around on the volcano. Now I know!

    • I did not know that… It tickles my triple-junction nerve. Volcanism always becomes more interesting at a triple-junction.

          • The okhotsk plate is the overriding plate where all the shallow (red) quakes are. The slab they conjecture is a particularly buoyant piece of the Philippine plate that has decoupled owing (they surmise) to the string of seamounts getting subducted here. This explains the seismicity and the kink in the arc. Fujisan possibly sits at the southern edge of this slab, with , like has been suggested for Etna, the slab tear facilitating the rise of deeper (mafic) melts to the surface.

            • Thought that was the Philippine Sea Plate 😕

              I’ll have to watch the video again 🙂

            • Actually, I need to correct myself slightly. In the video they maintain that the slab is a piece of the Pacific plate “whereas others maintain it is deformed Philippine plate”.
              Personally I think the others might be right. If the PP is not subducting, then where is it going?
              in the video they call the Okhotsk plate the Eurasian plate.

    • Thank you. The Tokyo area is at the junction between four plates. It gets slow motion earthquakes: between 28/12/2013 and 10/1/2014 there was a 10cm slip over two weeks (the equivalent to a 6.5); and, a one metre slip in late 2011.

      Source: “Slow motion earthquakes make big Tokyo quake more likely”, Shinzaburo Ozawa in the New Scientist, 26/04/2014.

      These slow motion earthquakes have been detected using GPS. Prior to GPS they were undetectable so it may not be appropriate to use slow motion earthquakes as a warning that a big earthquake is more likely. That said, the area has had devastating quakes so is closely monitored, especially following the Tohoku 2011 earthquake.

        • on the map above it looks more like a double triple junction – with boundaries like the lines of the letter H and mount fuji being on the west most junction

        • The thing about triple junctions… they are inherently unstable. Many configurations result in the actual junction traveling down one of the fault systems until it achieves a semi-stable configuration. This is what happened when the Farallon plate went kaput. The resulting junctions migrated north and south until they became somewhat stable in their orientation. Mendocino is the result of the northbound one, and somewhere near the Rivera microplate is where the southbound one ended up at.

          From Global Tectonics 3rd edition:

          A more complex and potentially unstable situation
          arises when three plates come into contact at a triple
          junction. Quadruple junctions are always unstable, and
          immediately devolve into a pair of stable triple junctions…

          And provides this schematic example, “T” means trench fault system.

          Many other configurations are possible from the Ridge (R), trench (T), transform fault (F) possible junctions. Most of them are unstable in some way shape or fashion.

          • Hm… I would not say this about the Tokyo Area and Mt Fuji “Quadruple junctions are always unstable, and
            immediately devolve into a pair of stable triple junctions”.
            The area is highly stable in being an unstable quadruple junction that for some reason does not devolve into a pair of stable triple junctions.

          • Do remember that the point of view of the author(s) is geologic time. As for stability, Japan is well known for it’s quakes.

            IMO, eventually geologic tendencies and processes will catch up with we feeble hominids, and if we are in the wrong place when the processes catch up and become manifest… well, thats something that the hominids in the way will have to deal with.

    • Grimsvotn, Hekla and Etna have produced VEI-5s (although Hekla and Etna have slightly different lavas).

        • Not really that peculiar. Keep in mind, describing Fuji as strictly “basaltic” is very much an oversimplification. I believe Fuji is more along the lines of Basaltic-Andesitic than strictly basalt as you would see in Iceland or Hawaii. The large eruptions likely start off with much more explosive magma, then devolve into large basaltic lava flows as the eruption goes on.

          Also, while they’re pretty rare, it’s very much possible to see plinian VEI-5-6 eruptions from primarily basaltic magma.

          • Fuji’s lavas have been likened to those of Mid ocean ridges. Her primary lavas are basalt and picro-basalt.

  6. Robert I had been suffering from a serious illness from at least 1327. The Lanercost Chronicle and Scalacronica state that the king is said to have contracted leprosy and died of it.[12] Jean Le Bel also stated that in 1327 the king was a victim of ‘la grosse maladie’, which is usually taken to mean leprosy.[12] However, the ignorant use of the term ‘leprosy’ by fourteenth-century writers meant that almost any major skin disease might be called leprosy. The earliest mention of this illness is to be found in an original letter written by an eye-witness in Ulster at the time the king made a truce with Sir Henry Mandeville on 12 July 1327. The writer of this letter reported that Robert I was so feeble and struck down by illness that he would not live, ‘for he can scarcely move anything but his tongue’.[12] Barbour writes of the king’s illness that ‘it began through a benumbing brought on by his cold lying’, during the months of wandering from 1306 to 1309.

    Police have named the man discovered hanging in Leechpool Woods in Horsham on Sunday (May 18).
    He is Robert Bruce, 38, of Ifield Road, Charlwood, Surrey.
    A police spokesperson added that an inquest has not yet been opened and adjourned.

    Police were called to the scene at 9.40am after a member of the public discovered the body.

    • Another event from IVAT

      Maybe this IVAT station is somewhat quite a distance from Hekla, so maybe this event is not related directly to Hekla?

    • It is not related to Hekla. I am though not sure at all what it is.
      The stations is fairly close to a hydropower plant so it could be something related to that.

      • Then where is the HT for the turbines? My toilet revealed the sonar fingerprint of the pump station up the road when I put an accelerometer on the fill line.

    • ROFLOL!!!! Bad guy tries to stop Kong from crawling out the throat of the volcano by literally lighting a fire under his ass. Yeah… sound logic. Most creatures redouble their effort at escape when presented with fire from the threat direction. Only man kind is stupid enough to rush INTO a burning building. Though admittedly, we tend to do so with some sort of protective gear, and it’s in an effort to help others get out.

      Note: The “stupid” characterization is not intended as to be disparaging to Fire Rescue personnel. I’ve done this myself, though admittedly, it was when I was quite younger and had the stamina to deal with the work load.

      It’s a Noble job, but you have to be a little bit nutz… and well trained, to successfully pull off a rescue without getting yourself killed.

  7. Beautiful image of Naples taken from the ISS at night. The city lights look like lava flows from dark Vesuvius.
    Image and video hosting by TinyPic
    ESA/NASA Id 299181

  8. Hello all! And hi KarenZ, I always love your articles, a good mixture of facts from several aspects, combined with your own plots, thanks a lot! And lucky you, actually having been there!

    Here is an update on Chaparrastique (San Miguel) Volcano in El Salvador:
    according to MARN (Special Report No. 148) there is a “Continued high probability for a third eruption of the volcano Chaparrastique”.

    I have read some details on various websites like twitter and Lave that there have been evacuations yesterday, and, due to recent heavy rains mudslides and/or a landslide on the slopes of the volcano. According To the MARN tweets there might have been a large landslide causing even higher seismographic signals on the volcano. MARN Twitter site:

    YouTube live video is on again (presently of the thermal camera):
    (if you live in Germany or a similarly funny country you might need the free ProxFlow tool [formerly ProxTube] to unblock and view the live stream.)

  9. I thought someone on here might find this interesting:


    GeoTenerife proudly announces that we have places available in AUGUST and SEPTEMBER on our summer internship programme, in collaboration with INVOLCAN, the Canary Islands Volcanology Institute, for undergraduates interested in the field of:

    *Environmental sciences
    *Communication and outreach

      • Welcome to the club . Tenerife, bunch of lucky Bas..rds. With a round trip to El Hierro to make gas samples maybe ? Alas, where are my twenties !

    • I think the ones we are seen now are from that last big EQ in the area. This might change if another 3+ EQ starts.

      They are very small and around the same depth and location as before.

      But yes, over the last year, I can see a trend that might mean something or nothing in the end.

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