CUEXCOMATE: FROM THE SMALLEST VOLCANO TO THE BIGGEST GEYSER ON EARTH

Completely surrounded by urban development in the city of Puebla, Mexico, the Cuexcomate sinter cone deposit has been mistakenly considered as a ‘small volcano’ by the local population for centuries. Its local name of ‘The smallest volcano of the world’ was coined because of its overall exterior cone-shape and its central crater. The Cuexcomate sinter cone has ~23 m in diameter, stands 13 m above the ground, and its ~4-8 m-diameter internal crater goes down ~4 m below ground (total depth ~17 m). Ambient-temperature water still flows in its interior, at the bottom floor, through a natural underground discharge, for which the path is unknown. Although no absolute ages have been obtained from this sinter, historical documents suggest and age of ~1060 years and correlate its formation with a peak in volcanic activity of the Popocatepetl volcano (~40 km to the West of the cone). The Cuexcomate had indeed a hydrothermal origin and can be compared in shape (not size) and composition to analog, currently-active geysers in the northern section of the Mexican volcanic belt, that are almost identical in composition to the Cuexcomate (90 % amorphous silica).