Some of you may have noticed that I haven’t been doing a large number of plots. In part, this is because digging into a large set of data takes a bit of motivation and patience… and a bit-o-time. KarenZ, dfm, and chryphia have picked up the mantle on animated plots, and have each brought their skills using their programs of choice and produced some truly outstanding animated graphics. This has allowed me to focus on learning and reading… sometimes getting it wrong, sometimes getting it right… or at least pretty close to right.
So… let’s ruminate.
Tolbachik is a fissure vent eruption. It wasn’t until this evening that I realized that my initial ideas about what happened were somewhat wrong. Rather than a sill forming (horizontal magma emplacement) which then fed to an upper sill via a dike (vertical magma emplacement), what happened appears to have been the pressure in already emplaced magma fracturing the rock and continuing along the path that it had been working on for several years.
Back in 1975, this system erupted in “The Great Tolbachik Fissure Eruption,” and according to the Smithsonian’s GVP site, placed 1.2 km³ of magma on the surface. For reference, that’s about 8% of what Lakagigar (Laki) did in 1783-85… and at about 11% of the rate. 2.26 x 10^06 m³/day verses Laki’s 2.02x 10^7 m³/day. Either way, it is still phenomenal. Mt St Helen’s did about 1 km³ in it’s flank collapse and lateral blast, but that was a different sort of critter. Tolbachik (and Laki) both do “Flood Basalts” though Tolbachik is a bit anemic in that regard.
However, it is cool to look at and ponder. Here is a combination EO-1 ALI image overlaid in Google Earth, with features aligned so that everything is in proper context draped over the surface.
“Dmitry Melnikov” over at Dr Erik Klemetti’s Eruptions forum spotted the EOS image.
As noted earlier, I had the sequence a bit off in how I was looking at it. (I’m not an expert so I’m allowed to mess up, right?) Poking around at the various links that show up in the threads, one gave us a bit of fine grained data… well, a lot more than we had. Doing a bit of data juggling, I located the data for the plot used in “Northern group of Volcanoes” It plots out like this;
Here you can clearly see the upper and lower sill/chamber and what probably is the connecting dike. It wasn’t until dfm did a close in animated plot that I noticed that the upper region seemed to initiate the events, and then the upper and lower regions pretty much quaked in unison.
Another thing that got my attention as I was poking around at it… was that the brunt of the quakes were no where near where the eruption was at. Maybe a few connectors from the main quake region, but that was about it. This probably is a manifestation of the feed system. (remember, “Bob” didn’t really have a lot of activity from the believed “chamber” to the Jacuzzi… which seemed to be seismically quiet until after the fact)
Juggling programs… (Excel to DivaGis to Google Earth) gives us this:
Notice anything interesting? Yup. Those two pancakes are directly under the main volcanoes. Roughly a line from Gora Bolshaya Udina to Mount Ostry Tolbachik. Had the dynamics been different, this could have been a main edifice eruption of Tolbachik. Even the seeming “connector dike” is directly under the SouthEastern summit. That pretty much means its actually connected with the vent. The magma just found an easier way out. (again, a lot like “Bob” where the main swarm of activity was pretty much under Tanganasoga but the eruption was over next to La Restinga)
Poking around the net… you find that Pay to Play paper sites can really piss you off. One of the most notorious is Springer… but Springer does have something quite neat. A few “freebie” papers that you and I (un-funded armatures) can get our hands on. One of them is: “Determining magma flow in sills, dykes and laccoliths and their implications for sill emplacement mechanisms” Thomson (2006). Here is the search link for it since direct links don’t work with that site:
In this paper, the author notes that sills tend to be concave upwards. That means that the propagating ends tend to point more and more towards the surface. A combination of forces can drive this, Forced Deformation, or Faulting. Page 197 of the parent publication (or just go to page 15 of the PDF) and you get a really nice visual example of what he is getting at. It’s entirely possible that something like this is what drove that finger of magma moving southward to turn up and broach the surface. (the tendency of this area to rift probably had a lot to do with it also)
Another thing to consider (speaking of tendencies) is that this entire region is made up of teranes that have been slammed into the Okhotsk plate (sort of a subsidiary of the North American Plate in some renderings) You all remember terranes right? Assemblages of crust material that have a common geologic origin and tend to move as a group. In this case, slivers of island chains squashed into the plate, slivers of oceanic spreading center remnants (the central valley region), an ancient volcanic arc (western side of Kamchatka), and … get this, parts of the Hawaiian hotspot’s activity. (up around Shiveluch where the Emperor Seamounts are periodically gobbled up by the current subduction zone)
Yeah… a lot of stuff going on in Kamchatka.
Here is an animated GIF I did the other night…. it was noted that this sped up sequence looked a bit like a frying pan fire. Appropriate.
Here is a re-tasked webcam where you can grab a peek at the activity from time to time.
RIDDLE – Name those Volcanoes
The sovereignty of first was briefly the subject of a ‘blague Francaise’
The second used to have vents (now pits) that share their name with a footballing legend – the name of this volcano means ‘long’ in the local language
The third is the only volcano within the arc of the SS islands chain to have erupted rhyolite pumice – Solved Protector Shoal
The fourth is located approx. 3 kms due west of a small group of ‘sibling’ rocks – Solved Kick ’em Jenny
The fifth shares its name with a species of lacertid – this giant wall lizard can only be found on the Island that bears the same name as the volcano
The link is that they are all submarine volcanoes!
One point for each volcano and one point for spotting the link!