December 20, 2012 | 3
Please sit down. I have some news to break. It may be very difficult to hear, and it may shake your innocence and trust. But I need you to know the truth.
Are you ready? Have you braced yourself? Okay, let’s have it: sometimes, the media is really terrible at science reporting.
I’m so sorry. But it gets worse: sometimes, they tell you things that really aren’t true at all.
There, there. Here’s a tissue and some reassuring pats. Back or head, or air-pats if you’re averse to physical contact but still want the gesture of reassurance, your preference. Deep breaths. I know, it’s hard, especially with the apocalypse not coming up tomorrow. But we can get through this. Together.
(I am done being sarcastic now. I reserve the right to engage in lighthearted snark throughout. This week has been grim, and it’s nice to relax and have a little fun.)
So one of my long-time readers and dear friend, RQ, sent me a link to the news about Tolbachik’s most recent eruption. Last time this volcano blew, I was just considering becoming a toddler and deciding to give it a miss for another year. Now it’s erupting again, and as if spectacular fountains of molten lava and five-story tall lava flows weren’t exciting enough, the media has to go and try to find something else incredible. And they don’t understand cinder cones in the least.
So, Tolbachik is one of the many volcanoes on Russia’s Kamchatka peninsula.
I’d not heard of it before, but I’ve just spent weeks getting to know a few other of Kamchatka’s feisty landforms quite well – Bezymianny and Shiveluch – so I was quite excited to learn a bit about it. The Kamchatka volcanoes are starting to feel like family. Tolbachik is a tiny bit of a weirdo – it’s a combo shield-and-stratovolcano. Before any onlooking reporters begin to salivate, however, I should note that it’s not that odd. Lots of volcanoes overlap, like the Three Sisters in Oregon – really, this is the equivalent of someone trying to stand out by wearing their cap backwards. They may look a little strange in a group of brim-first ball cappers, but it’s not like there aren’t lots of others just like them. In a subduction zone, you can expect all sorts of shenanigans.
By now, you’re wondering where cinder cones come in. Well, they’re all over Tolbachik. Some lovely examples were formed back in the 1975-1976 eruption (warning: the helicopter noise is quite loud):
Tolbachik erupts a lot of basalt, and basalt’s really very good at forming cinder cones. But no, this isn’t the unusual thing. Cinder cones form on and around a lot of stratovolcanoes. Head up to the Dee Wright Observatory and you’ll see them all over the place, along with the Sisters, one of which is built of both a shield volcano and a cinder cone, with some lava flows on top.
RQ said in an email, “The Latvian article mentions that the volcano’s cinder cone exploded during the eruption… Are they getting their science right (apparently it’s an extremely rare occurrence)?”
In a word, no. RQ was right to be suspicious. I actually giggled when I read what they were saying (well, the translation of what they were saying – in Latvian, I’m illiterate). For people like RQ, who are just now learning about volcanoes, it’s mystifying, but to folks who grew up in places like the San Francisco Volcanic Field, it’s hilarious. I had a bit of a volcano phobia as a kid, but I never ever was scared of the cinder cones. They were done. They’d put on their show, and they were now defunct. They’re what’s known as monogenetic – they erupt once, perhaps for days or months or a few years – then they’re spent. Finito. No more esplodey.
What’s probably happening on Tolbachik is that the new eruption is happening very close to an existing cinder cone, perhaps even building a new cone the flank of the older one. It’s not unusual for cinder cones to overlap. There’s a fine example in the West Potrillo Mountains of New Mexico, where a new cone barged up between two older cones and partially buried them. Cheeky! It’s not uncommon to find four or five cones all piled up together in the Potrillo volcanic field.
The parasitic cones on the flanks of a stratovolcano have even less room to be individuals than those in a nice, roomy volcanic field of their very own. The cones formed by activity there are generally smaller and spaced much more close together.
Which brings me to the next bit of silliness, from the English-language report RQ found for me:
The volcano, which is located in Russia’s Kamchatka region, erupted in an unusual way – the lava and ash flowed not out of its main crater, but from the volcano’s sides.
I have sympathy for reporters tossed willy-nilly at breaking stories on geological matters when they have absolutely no prior expertise. If all you know of volcanoes is dimly-remembered diagrams of them from early childhood education, then yes, you’re going to be pretty shocked that volcanoes erupt from their sides. But it happens all the time. You remember our own dear Mount St. Helens, which had domes bulging all over her flanks, and probably hadn’t blown her top for several hundred years. Yes, the lateral blast took us by surprise then – we hadn’t realized how many volcanoes blow catastrophically out the side – but if she’d popped a new dome or even a cinder cone from any point on her sides, volcanologists wouldn’t even have blinked. That’s what volcanoes do. Magma works its way up the main conduit, and quite often finds a nice set of fractures it can exploit instead, and it can pop out at any point along those fractures. Sometimes it even marches up and down the fracture zone during a single eruption – it happened at Vesuvius in 1906, Kilauea in 1959-1960, and Mount Etna in 1928 and 1971, for starters, and that’s just a small sampling in the literature (shamelessly filched from one paper). Some volcanoes’ flanks are lousy with cinder cones from those eruptions. We can tell where the fracture zones are by looking at how the cinder cones are aligned. It’s neat!
This is a perfectly ordinary eruption, but it’s quite lovely, and tourists are taking spectacular video, so this is a treat – we get to see a fissure eruption evolving toward creating a cinder cone, and it helps us understand more about the life cycles of these very feisty fire mountains.
It also gives us a chance to snicker at incorrect media reports, which is always great good fun for those who love pouncing on mistakes. I apologize to those who have seen such volumes of misinformation spewed forth like scoria from a birthing cinder cone that they can no longer laugh, but merely whimper whilst tearing at what’s left of their hair.
Hoffer et al (1998): Qualitative relationships of late Cenozoic cinder cones, southern Rio Grande rift, utilizing cone morphology and Landsat thematic imagery: A preliminary assessment. In Las Cruces Country II, Mack, G. H.; Austin, G. S.; Barker, J. M., New Mexico Geological Society, Guidebook, 49th Field Conference, pp. 123-128.
Settle, Mark (1979): The Structure and Emplacement of Cinder Cone Fields. American Journal of Science, Vol. 279, p. 1089-1107.
And don’t forget to keep up on current news from Tolbachik’s eruption at Erik Klemetti’s excellent Eruptions Blog.