Onekotan volcano complex

Photograph by Alexander Belousov.

The island of Onekotan lies to the south-west of Kamchatka, near the northern end of the Kuril island arc. The uninhabited island (excepting several Russian border guards), c45km x 7-15km across, contains two, at-present quiescent, active volcanoes, with Mt Krenitsyn in the south, the highest point at 1324m and Nemo Peak – 1019m – in the north. Both peaks are central volcanoes associated with large calderas, the peaks being developed within the caldera remnants.

Astronaut photograph ISS026-E-16287 was acquired on January 9, 2011, with a Nikon D2Xs digital camera using an 180 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 26 crew., NASA-JSC.

The Kuril arc, part of the circum-pacific volcanic belt, began development to the west and north-west of the Kuril Trench during the Cretaceous Period (c90myrs BP) where the mobile Pacific plate subducts beneath the Okhotsk plate. In common with such locations, explosive andesitic volcanism is dominant. The Pacific plate has an approximate north-westerly progression rate (at present) of c8mm/yr, the subduction shear being at a depth of about 120km below Onekotan; with the island arc/trench distance at around 300-350km. The crustal thickness beneath Onekotan has been estimated at 20km.

Picture from: http://www.lkirchner.de/onekotan/onekotan/coast_and_nemo/coast_nemo.html

The pre-glacial form of the northern eruptive centre of Onekotan comprises an andesitic composite stratovolcano complex of two semi-concentric but overlapping calderas, the largest of 10km diameter. A third caldera, from about 25000years ago, destroyed a cone built within these calderas, with the present twin-peaked Nemo Peak developing within this latest structure, along with the crescentic Chernoe Lake.

Tephro-chronological dates from earlier historic and pre-historic central vent eruptions have been listed (from GVP) at (approximately) 9550, 9050, 7550, 5050, 3850, 2500 years BP and 750 and 1350AD.

Within historic times, moderate explosive eruptions have occurred in 1710, 1906, ?1932, and 1938, with subsequent fumarole/thermal activity.

The southern part of the island is dominated by the spectacular combination of the almost circular Tao-Rusyr caldera with the subsequently developed symetrical cone, Krenitsyn, within the 7km caldera-lake, Kal’tsevoe.

Mount Krenitsyn. Image by Dr. Igor Smolyar, NOAA/NODC.

The 7.5km diameter caldera was formed c7500 years ago (from radio-carbon dating) by chamber collapse following a VEI-6 eruption; one of three VEI-6 eruptions in the Kuril arc (here classified as producing 10-100km^3 total ejecta) in the period 9400-7500 years BP. In addition there have been, since 1712 when the area was first exploited, ten VEI-4 eruptions in Kuril arc.

The strato-volcanic cone of Krenitsyn peak, 1325m high and 4km in diameter, is composed of andesite-basalt. Krenitsyn has a 350m wide-100m deep summit crater, and a subsidiary crater on the north-east flank.

At present it has been quiescent since the emplacement of a small lava-dome from a lateral conduit in the cone at lake-level in 1952, a short time after a M9 earthquake along the subduction fault, since when only thermal/fumarolic activity has been observed.

ALAN C

P.S. Keep the questions coming for the Q&A on GPS:s in Iceland. D.S.

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990 thoughts on “Onekotan volcano complex

  1. @islander, Have you seen the GPS measurments from raunvis.hi.is. May have some inflation.

    • The biggest fecal pellets ever seen… :-)
      Geez, that’s my first comment of the day and it goes strait into the low level stuff. Worst thing: computerwise it’s my second action after checking earthquakes and tremor in Iceland. This will be hard to cure. If my wife kicks me because of too much volcanoing, at least I keep hope that Diana will also be free again… ;-)
      Oh, and let’s be polite: good morning all. Today might be “the day”.

      • Good morning!

        She does look good!:

        [url=http://bildr.no/view/1160146][img]http://bildr.no/thumb/1160146.jpeg[/img][/url]

        • Rescued by Spica !
          Placing Images like this does not work and will end up in the spam vault.

        • I prefer thinking it was a short period with meters tall foraminifers that came out of a genetic mutation induced by a fat CME. Then the mexican food issue and so on and that’s the result.
          If that is not enough to fish some good piece of 2012er, I don’t know what to do more. But I really think we should have something crispy to feed our dragons one of these days. I mean, I also feed my Jack Russell every day…

          • I once was at a demonstration of people that make iron stuff. Could buy a “rough” iron-pan for good money. Why did I buy such a thing as I have a modern kitchen? Couldn’t help myself dreaming of using it on a lava with enough rest-heat sometimes in the future… :-)
            Bought it 10 years ago and still didn’t use it. But I know where it is in the house…

          • And we’re glad about that.
            Just like to fool around with that. They are such an entertaining kind, as well as are their fantasies. Just too bad they are not clever enough to be really fascinating…

    • And I like Burfell’s kind of large-scale regular “oscillation” look since monday afternoon.
      It’s just about the look. :-)

      • Please can someone explain the measurements on the y axis on the additional strain meter graphs ….I sort of have a vague concept but a nice simple explanation of what for example 2e + 03 means. I understand that the strain meter reads per second but I am sure I am not the only one who find this a bit of a mystery.

  2. Good morning everyone. (Waves at GeoLoco) :D Funny I always check the Iceland map first too :D Humans are such creatures of habit. This morning I have to rush off . Husband forgot to take the Rubbish bins to the top of the lane. It is collection day today. It’s a hard pull up the lane with full bins especially if one is height challenged!I am convinced that most inventors and developers are tall, Most things are set too high for me…..I am just 5ft and shrinking.

    Peloche and Tor …lovely pictures thank you. Hekla does indeed look beautiful…We have a saying in the UK “Red sky in the morning , a shepherd’s warning. Red sky at night, a shepherd’s delight”. Red sky as the sun rises usually heralds bad rain :D

    • Hi there!
      Red sky – moisture / clouds. If in the west, with often winds from west, there’s high probability for this moisture to come over us during the following hours. If the “disturbance” has passed and is in the east in the evening, there are good chances for nice weather to come… Always interesting to think what could be behind such sayings. Some are bulls…, but some work out quite well. Tested that for the alpine weather evolution. Often correlates with big scale climatic stuff when they make “seasonal predictions”. And on the local scale some signs (when the clouds come from left or right of that mountain etc…, then blablabla) are as accurate as a lot of complex models… :-)
      Concerning the height thing: tried high-heels? ;-) I hate them – girls walk unnatural with them, looks like they were some how challenged and unhealthy, makes then potentially bad for the whole breeding issue – us being primates and reproducively interested animals, we have to look healthy to attrackt a “sane” partner. I’d always go for a girl in trekking shoes or sneakers with a nice pair of jeans or outdoor pants than for one that will starve and freeze in her mini-skirt 2.5 hours after the first blast of “Hell’s gate grand opening at Bardarbunga (TM as Carl would write)”. But we all have our taste and none is better than the other of course.

          • Geoloco, stick with the fish in boots/sneakers/shoes rather than high heels. The personality tends often (but not always) to go hand in hand with dressing style (very roughly). Too much beauty dressing at every day, often points to superficial personalities, that´s what I often experienced. But there are exceptions of course.

          • Irpsit,
            Join you about that tendency. But it’s also about what one looks at. A nice pair or cheeks is a nice pair of cheeks, no matter if it’s wrapped by a mini-skirt or jeans. I mean, what is it that makes “beautiful”? The content or the wrapping? I’m quite a content-guy.
            V8 twin turbo in an ugly break or small engine in a coupé shaped whatever? Erm, I drive the engine and suspension, not the chrome or radio/MP3/bluetooth/DVD/whatever entertainment system… That was a manly comparison, wasn’t it? :-)

    • Just checking in: like Diana I always check the Iceland map first. I’m also a bit on the short side and agree most designers must be tall men. I have to dash off for training – it’s pouring with rain and I have to get to the other end of the building (1/8 of a mile long)! Catch up with you all after lunch! TTFN! :-)

    • I totally understand, Diana, I used to be 5ft and ‘a spit’ – now I hate to think what I am….. probably only just hitting 5ft. Pushing garbage bins is a pain; shopping trollies are also harder to steer when one is shorter (yes, I know they make them hard to steer on purpose!); reaching stuff on the highest shelf at the supermarket is impossible (that’s what my 6ft 3in Ex was for!). My lastest peeve is that I can’t reach the light above the mirror in this ***ing Paris apartment! Thank heavens I’m not one of the ‘image brigade’ – don’t care if my lippy is a little wonky!

      • LOL Kathryn…. The top shelf at supermarkets is out of bounds for me…. So I smile sweetly at the nearest smiling young man. :D….You are never too old even if you are on the short side………. :D My Lippy is always wobbly…..comes from spending too much time watching borehole strains :D

  3. Another clear sky, sunshine calm morning in South Iceland, but now white due to snow layered.

    Unrest seems stronger at STO. I wondered if this is:
    1) related to vatnfjall volcano
    2) or precursor to large earthquake east of Hella or Árnes
    3) something in volcanoes southeast of Hekla (Tindfjall, Torfajokull or Katla)

    Doesn’t seem much Hekla to me now.

    • We all looking at Hekla and it could turn out being a window to see something cooking at Katla. Would be a very nice draw by those 2 ladies. :-)

  4. Carl. We are getting close to 1000 comments on this post.
    What if we prepare a few posts as drafts to go in in such occasions. Any dragon could publish them then. Because it is absolutely understandable you dont want to add a new post on Hekla right now.

    • And if there was just a “blank post”, titled “comments and entertainment waiting for Hekla or Katla to clear their intentions”? ;-)

    • I am going to put in a new post today.
      But I can not say exactly when and what really. I think I will either do the post debunking large earthquakes causing eruptions or massive fails on distant plate-intersections (takes a bit of time to write), or a short pieve on the Icelandic SIL and how to read them.

    • Not really, if you remove the quakes that belong to/originate with the Godabunga cryptodome there are only four quakes of which the three most recent are of very low “quality” (30.52 – 37.61%). Such low quality means that everything; location, depth, magnitude, will change if and when IMO have a look. also, four quakes in the last 48 hours is low-to-average for Katla. Just go back to

      Here are a few hints about how to interpret quakes at Katla:

      * Quakes that may be important get looked at right away by the seismologist on duty at the IMO. If they don’t investigate a quake quickly, they attach little importance to it and so should we
      * The IMO automated system assigns a default value of 1.1 km in case there is no clear indication of depth
      * The Godabunga cryptodome, a very active system indeed, lies just outside the Katla caldera and is not part of Katla’s volcanic system. Almost every quake to the west, including some inside the caldera, are not “Katla-quakes” but “Godabunga quakes”
      * The ESZ runs through the Katla caldera, so purely tectonic quakes do occur
      * From top to bottom, there are three types of quakes (in addition to any purely tectonic quakes): Icequakes associated with seasonal freezing or melting of the icecap, quakes in the hydrothermal zone ~0.7 to ~4.5 km depth according to the professional seismologists at IMO, and volcanic earthquakes which usually are at a depth greater than ~4½ km

      This is from (my memory of) an interview with one of the seismologists at IMO and if you (generic) so to speak “look through her eyes”, there’s nothing going on at Katla right now.

      • many thanks Henri. Nicely explained. I tend not to get too excited unless all the SILs round Mydrdalsjokull show major increased activity. Hekla? Who knows…..I just enjoy looking at that mountain in all it’s moods.

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