This has to be one of the strangest volcanoes I have ever encountered.

Though I live in west Texas which is a desert where there are abundant volcanic rocks dated between 30 and 45 million years ago, none of the original volcanic edifices are readily identifiable, yet here is a structure which actually looks like a volcano but which has radiometric ages of approximately 77 million years. It is more than 650 m high, with a deep crater almost 2 000 m in diameter, it has a flat, rock - littered floor. The entire structure being about 10 km across.

One interpretation of the structure is that it was a large diatreme which erupted in a phreatomagmatic fashion. An alternative explanation is that the intrusion of a shallow magma chamber led to updoming of the pre-existing rocks. Over the course of time, repeated eruptions from the magma chamber led to collapse of the center of the overlying dome.

Adding to its weirdness, the magma which produced the volcano was carbonatitic in composition. Diatremes and dikes in the immediately surrounding countryside are all carbonatites and a carbonatitic lapilli tuff has recently been described from Brukkaros itself. Carbonatite is the most silica-depleted magma found in alkali volcanic provinces which are almost exclusively continental.

For a short while the mountain housed a solar observatory but the sky proved to be too dusty and it was moved.

The stamp below was issued on July 18th, 1991

Stamp courtesy of Lisa Heiman

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