The flu has retreated and I'm getting back on track. Huzzah!
I'll get back to the blog by posting this week's new USGS / Smithsonian Institution Global Volcanism Program Weekly Volcano Report. Looks like some interesting stuff in it ...
- Looks like there were some small eruptions from Oldoinyo Lengai in Tanzania. The volcano is one of the few (only active?) carbonatite volcanoes in the world, erupting a lava composed primarily of calcium carbonate and sodium minerals with very little silica. It leads to the odd lava that erupt black (and cool ~ 500C) and cool to white, making it one of the strangest places on Earth.
- El Reventador in Ecuador appeared to produce some ash and a thermal anomaly was detected as well.
- Russia's Kliuchevskoi produced strombolian eruptions along with some phreatic (water-interaction) explosions related to a lava flow.
- Back in Ecuador, Sangay produced an ash-and-steam plume that reached upwards of 7.6 km / 25,000 feet.
- The level 3 (of 4) alert at Talang in Indonesia was reduced to Level 2 as seismicity has steadily declined since February 2009.
Those carbonatite volcanoes are very interesting. Every few years I go to the Kaiserstuhl volcano in the South of Germany. That volcano is part of the Upper Rhine graben (mentioned in the article Erik linked to) and although the rifting process still takes place there, the Kaiserstuhl has not been active for around 15 million years. It's still a nice place to go look for a big variety of volcanic rocks. The Limberg for example, is a small stratovolcano that's part of the Kaiserstuhl complex. It's the type locality of Limburgite. In the center of the Kaiserstuhl a big mass of carbonatite can be found. Carbonatic lapilli tuff can be found around places where there used to be craters.
Erik, glad you are feeling better.
@Gijs, what is Limburgite? Can you give a description of it? I may be a rock hound, but I sure don't know about a lot of rocks and minerals.
I think Oldoinyo is one of the weirdest places. I have seen films and pictures of it and it is something else. The lava, in the films I saw, just globbed out and also acted a bit like Stromboli, but on a very limited scale; like little burps of stuff and forming hornitos. Yeah, I know I am talking about what most of you know anyway, but it is cool to see what it does.
It's a rock that looks pretty much like basalt, but it contains no or almost no feldspar, and nepheline is also rarely found in it. Limburgite can be found in volcanic areas all over the world, although there are some differences in appearance depending on where it comes from.
My nicest specimen: http://img534.imageshack.us/img534/2597/limburgietlimberggroeve.jpg
Glad you're feeling better!
Oldoinyo Lengai is one of my favorites. I flew over it in 2006 in a small plane and got a couple of good pictures. It's the only active carbonatite volcano left on the planet. The lava erupts much cooler than most volcanoes (500Â°C to 600Â°C), so it doesn't glow during the day. As it cools, it reacts with moisture in the air and turns white.
It's actually been experiencing a phase of explosive eruptions lately, which it does a couple of times a century, but they seem to be abating and the mountain is returning to its normal modus operandi. It'll be a good number of years before you can walk through the erupting crater again, though.
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