19 comments on “Another Hot Spot: Mt. KARTHALA, Comoros

  1. Very interesting article Granyia. Your article comes now in 5th position in Google. The adjacent island of Mayotte is also of volcanic origin, but the volcano seems extinct. It was made into the 101st french department only a few years ago.

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    • Thanks dfm, I was amazed that Google found us at all when I had forgotten to assign any keywords – must be nearly 1st now 😉 I have read about the Mayotte people having chosen to stay with France. I have also seen pictures with banners screaming the Island belongs to the Union, and I have read very personal raging comments about how France dare to not hand Mayotte over. I am all for the freedom of choice for every people, and I am all against countries occupying land that doesn’t belong to them. The bad thing is, you never know as an outsider what has gone on behind the scenes? Did the Mayotteans really want to stay with France – and if yes do they still want to, or have they changed their mind? Or was there great politics/blackmailing at play under cover? I am pretty sure, though, that the Island is better off with France (depending whether France is looking well after her overseas departments).

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      • Hi
        Mayotte has a very high number of illegal immigrant coming from the Comores, several thousands a year. And yes France takes care of its overseas department (even if it is far from perfect of course). Having been in Dominica, Guadeloupe and Martinique, I have seen the gap. I’m not naïve tough, having these islands is far better than having an aircraft carrier 12000 km from the mainland.

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    • Hmm… what search term did you use? With “StartPage” (google engine, but without cookies etc.) and “Mt. Karthala” we are not amongst the first 100. “Karthala hotspot” flings us on #2 though 😀

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      • It’s probably one of google’s little quirks, I cannot redo it now….
        I’m using more and more duckduckgo because of this.

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  2. Excellent and thought provoking article. Interesting that :La Grille has no caldera, no historic activity, and plenty of cinder cones. On the face of it, sounds like the Mauna Kea to Karthala’s Mauna Loa -any thoughts? Is there anything published to identify chemical differences between the products of the two centres?

    And a rather odd query. Why does Grande Comore have WHITE sand beaches? Unless they are shell sand like those in Scotland’s Hebrides. Sand usually is quartz, not something to be present in large amount on a basalt shield

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    • Hi Michael, thanks! There is not much out there that a mere mortal like me can understand easily; one may find the La Grille volcano mentioned in discussions of magma compositions from deeper mantle (mantle plume) vs. lithospheric mantle sources etc. Just this seems to be the case here: The Grille’s magma stems from the upper mantle like any “normal” volcano’s while Karthala’s magma has signatures that are only found in deep mantle sources, and somewhere on its way up the plume magma becomes mixed with the lithospheric. Although the two volcanoes are thought to be contemporary, I think Grille must have its own source. Remains the question, how magma melting and ascent would be induced for it to erupt. This might be explained here The Process of Plume–Lithosphere Interactions in the Ocean Basins—the Case of Grande Comore but it will take me a good while to read and understand this paper.

      As to the sand – I have read in this paper that the ocean floor around and below the Comores consists of a layer of over-2km-thick “quartzarenitic” basin sediment, eroded from the African continent. This could perhaps account for sand beaches washed up by the ocean waves. Looking at Google Earth, there aren’t that many white beaches on Grande Comore, mainly at the S and N ends, the rest of beaches is dark grey as one would expect.

      Btw., the latter mentioned paper “Caldera collapse on basaltic shield volcanoes: analogue models compared to the Karthala caldera complex, Grande Comore” by Sam Poppe is a very commendable read for anyone wanting to know more about how calderas form. I will put the link in our “Basics” section.

      EDIT: I forgot to mention that there are also coral reefs offshore Grande Comore which of course could be source for sand on the beaches. Although on the satellite images the sand looks rather dark yellow or ocre, but you never know with processed images.

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  3. Another EQ in central Italy that must be devastating: M 6.6 with a depth of just 1.5km uncertain (USGS, probably preliminary). This is the EQ map of the last 7 days – strange how they are aligned in an oval…

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  4. And back to volcanoes: Nevados de Chillan is still throwing tantrums…

    …and Fuego is having a good time too, it showed great fireworks on the webcam all night and apparently there has been a PDC (pyroclastic density current) this morning

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  5. Lava flowing constantly now on volcan Fuego, this has been going for at least half an hour

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  6. More und better images from space coming soon:
    The Himawari-9 meteorological satellite was put into orbit on Wednesday after a successful launch of an H-2A rocket carrying the satellite at the Tanegashima Space Center in Kagoshima Prefecture. The satellite is decorated with illustrations by mangaka Chuya Koyama, creator of the famous “Space Brothers” series. The cartoon images are actually made of about 30,000 tiny photos and illustrations of space-related themes collected from children and arranged in a mosaic.

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  7. Found this basic Igneous Rock Description Chart on Twitter, great for a quick reference when reading about volcanic products. I’ll post it on our V-Basics page.

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  8. Wow, what? Huge “lake” discovered 15 kilometres under Uturuncu volcano – the unexpected water, which is mixed with partially melted magma, could help to explain why and how eruptions happen. This water may also be playing a role in the formation of the continental crust we live on, and could be further evidence that our planet has had water circulating in its interior since its formation…
    Article
    https://www.newscientist.com/article/2111460-huge-lake-discovered-15-kilometres-under-volcano/?utm_medium=Social&utm_campaign=Echobox&utm_source=Twitter&utm_term=Autofeed&cmpid=SOC%7cNSNS%7c2016-Echobox#link_time=1478381410
    Paper (paywalled)
    Giant magmatic water reservoirs at mid-crustal depth inferred from electrical conductivity and the growth of the continental crust
    http://www.sciencedirect.com/science/article/pii/S0012821X16305805

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  9. Continuous ash emissions up to 1500m from Sabancaya (PE) volcano for at least several hours:

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