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

Gerenuk: the Giraffe-Necked Gazelle With A Stone Skull

           The gerenuk is a long-necked gazelle, also known as the Waller's gazelle, that lives in eastern Africa:

           I've been perusing lists of wild mammals who are not native to North America for the NPR Sunday Puzzle and discovered this beautiful beast with wonderful coloring

and a sweet face:

          The word gerenuk is from the Somalian word garanug meaning a long-necked or giraffe-necked gazelle. The genus and species name Litocranius walleri
is from lithos, Greek for stone (so, of course, I was even more curious) and kranion, Greek for the upper part of the skull. The "stone skull" is a reference to the skull which is almost solid bone at the base of the horns.

       The Waller's gazelle is named for the Reverend H. Waller (1833-1901), a friend of the infamous Dr. Livingstone (I presume).

           Reverend Waller spent much time in this part of Africa with the gerenuks:

          The gerenuk feast on leaves, fruits, and plants, especially those higher up in the desert brush. They like to browse together in groups but have little need for a water cooler to gather about as gerenuks almost never drink water, getting most of their water from the food they eat.

          In ancient African tribal tales, the gerenuk has been crowned "Queen of Humbleness" due to their looking out for one another. . .and never needing an "Attaboy or attagirl." ;-)

Seen any gerenuks (or other interesting mammals) lately?

Steph