This rambling journey all started a post from Atlas Obscura (a really great site for wasting huge amounts of time on fascinating, relatively unknown items from around the world). It mentions a unique volcano in northern Tanzania, Ol Doinyo Lengai, which spews carbonatite lava instead of the usual silicate magma.
Magma is still magma - hot, molten rocks, but the lack of silica in the magma is very unusual. This is the only active volcano in the world that has carbonatite magma (more on the inactive volcanoes in a minute). Silica, as you may know, is capable of forming long chains thereby increasing the viscosity of normal magma. It also increases the temperature at which the magma needs to be heated in order to flow. Carbonatite magmas cannot form such long chains, so their magmas can be of lower temperature (500 oC vs. 1100 oC) and viscosity. (At 500 oC, the stuff isn't even glowing red!) And it appears to freeze pretty quickly, leading to some exotic formations:
The Atlas Obscura article is pretty short, but some more digging turned up some further fascinating connections. The Wikipedia page for the volcano states that
"The carbonatite ash spread over the surrounding grasslands leads to a uniquely succulent, enriched pasture. This makes the area a vital stage on the annual wildebeest beast migration, where it becomes the nursery for the birth of several thousand calves."And further digging led me to this article by a Dennsion University Professor. The whole basis for some volcanoes being silicic and others being carbonic is still unresolved. Weirder yet is that Ol Doinyo Lengai used to be silicic and only recently has become carbonic. And still weirder yet is that carbonic magmas are associated with deposits of rare earths elements. The largest rare earth mine in China as well as the rare earth mine in the US are both located in carbonic deposits, and rare earths are crucial components for smartphones, supermagnets and other items of modern technology.
Prior to this, I never new that there were such variations in magma, let alone that they would have such profound impacts for those of us living on the surface of the planet.