Carbonatite: "Sandcastle" Structures in Calcium Carbonate-Rich Tanzanian Volcano

         Carbonatite lava is quite unusual in that it is dominated by calcium carbonate, rather than silica, as is most of the earth's lava. It creates these delicate structures, reminiscent of giant sandcastles:





        This 2-minute video of  carbonatite lava erupting in Ol Doinyo Lengai Volcano, Tanzania, Africa, shows the extremely liquid, less viscous nature of the carbonatite compared to the thick, ropey, silica-rich pahoehoe lava of Hawaiian volcanoes.

         Ol Doinyo Lengai is the only known, currently erupting carbonatite volcano on earth. It is located in the East Africa rift zone.

          Carbonatites are, almost exclusively, associated with continental rift-related tectonic settings.

         Unfortunately, structures like those seen in the first image above are, like sandcastles, extremely delicate. The structures, as such, are rarely found in the rock record.

     
        Because of its unusual composition, carbonatite is quite literally the coolest lava on earth, erupting at 500-600 degrees Celsius (930 - 1,100 degrees F), compared with 1,160 degrees C (2,120 degrees F) for lava from silica-rich volcanos.

  

How cool is that?!

Field trip to Tanzania, anyone?

Steph