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Cuexcomate beraldi
- 1. CUEXCOMATE: FROM THESMALLEST VOLCANO TO THE BIGGEST GEYSER ON EARTH Institute of Geology, UNAM. Ciudad Universitaria, 04510 Mexico DF Hugo Beraldi-Campesi hberaldi@unam.mx SUMMARY Completely surrounded by urban development in the city of Puebla, Mexico, the Cuexcomate (from the Náhuatl ‘cuexcomatl’, meaning ‘bucket’ or ‘pot’) geyser cone deposit has been mistakenly believed to be a ‘small volcano’ by the local population for centuries. The concept of ‘volcano’ was coined because of its dome-shaped exterior and its central crater, similar to a volcano. The Cuexcomate is a chemical (calcitic) hydrothermal deposit (geyserite) of considerable size: ~28.5 x 24.3 m in diameter, stands ~8.4 m above the ground, and its ~10 x 5 m-diameter internal crater goes down ~4 m below ground (total depth ~12 m). The roomy interior serves as cultural/touristic attraction. Ambient-temperature water still flows in the bottom interior, connecting with a natural underground discharge of unknown path. Although no absolute ages are known for the Cuexcomate, Puebla’s municipal government sustains that the Cuexcomate was originated ~948 years ago, in 1064, and was reactivated ~349 years ago, in 1664. Important peaks of activity of the Popocatépetl volcano (~40 km to the West of Cuexcomate) before the year 1900, occur approximately 349, 493, and 5712 years ago. It is unclear whether the Cuexcomate was formed during Popocatépetl’s mild activity or not. Radiometric dating is needed. The Cuexcomate clearly had a hydrothermal origin. It can be compared in shape, texture, and composition to analog, currently-active geysers around the world. Yet none compares in size with the Cuexcomate; the largest being ~5 m tall. The non-reported-yet Apaseo sinters (North of the Trans-Mexican Volcanic Belt) are used here to compare different mineralogical compositions (Cuexcomate = 90 % calcite, Apaseo sinters = 90% amorphous silica) with similar shapes and origins, typical of hydrothermal deposits in which the underground basement defines the composition of the precipitates. Data on Cuexcomate’s chemical composition are presented here for the first time. CONCLUSIONS -The Cuexcomate represents the oldest evidence of hydrothermal activity reported for the Popocatepetl volcano. -Because the Cuexcomate had a hydrothermal origin, it denies the historical idea that cuexcomate is a volcano. -The Cuexcomate is established here as a geyserite deposit of 90 % calcitic composition. ACKNOWLEDGEMENTS This study was possible thanks to Puebla’s City Council, Carnes Canet Miquel, Institute of Geophysics, UNAM, and Teresa Pi Puig, Institute of Geology, UNAM. Popocatépetl 5426 masl Last active: 2012 Iztaccíhuatl 5230 masl Last active: >80,000 yr BP? La Malinche 4461 masl Last active: 3182 yr BP Puebla 2 4 6 8 10 -7500 -6000 -4500 -3000 -1500 0 1500 EruptiveCharacteristics Eruptive Characteristics: 1. Central vent eruption 2. Explosive eruption 3. Pyroclastic flow(s) 4. Lava flow(s) 5. Lava dome extrusion 6. Fatalities 7. Damage (land, property, etc.) 8. Mudflow(s) (lahars) 9. Evacuation Birth of Cuexcomate? 1064 1996 Time (years) Eruptive history of the Popocatépetl volcano Data from the Global Volcanism Program (GVP). http://www.volcano.si.edu/info/ 2 4 6 8 10 -7500 -6000 -4500 -3000 -1500 0 1500 EruptiveCharacteristics Eruptive Characteristics: 1. Central vent eruption 2. Explosive eruption 3. Pyroclastic flow(s) 4. Lava flow(s) 5. Lava dome extrusion 6. Fatalities 7. Damage (land, property, etc.) 8. Mudflow(s) (lahars) 9. Evacuation Birth of Cuexcomate? 1064 1996 Time (years) Eruptive history of the Popocatépetl volcano Data from the Global Volcanism Program (GVP). http://www.volcano.si.edu/info/ 1 2 3 4 5 1300 1400 1500 1600 1700 1800 1900 2000 RelativeExplosivityIndex Time (years) 9 1519 Birth of Cuexcomate? 1663 19191919 1996 Eruptive characteristics vs. Volcanic Explosivity Index EC VEI Data from http://www.volcano.si.edu/info/ 1 2 3 4 5 1300 1400 1500 1600 1700 1800 1900 2000 RelativeExplosivityIndex Time (years) 9 1519 Reactivation of Cuexcomate? 1663 19191919 1996 Eruptive characteristics vs. Volcanic Explosivity Index EC VEI Data from http://www.volcano.si.edu/info/ Weathered texture 3 m Ground level ~12m flow Crater 01 04 03 02 05 Cuexcomate seen from above. Courtesy of Google Earth. Wikipedia.com Viajeros.com 0 0.2 0.4 0.6 0.8 350 850 1350 1850 2350 Wavelength nm Absorbance% 01. Base 02. 5 m 03. 1.3 m 04. 1 m 05. Exterior 06. 300 m apart 1445 1937 2354 0.1 0.2 0.3 0.4 0.5 350 850 1350 1850 2350 Wavelength Absorbance% Cuexcomate Apaseo 0 500 1000 1500 2000 2500 4 9 14 19 24 29 34 39 44 49 54 59 64 69 2 degrees Counts Cuexcomate, exterior upper surface Calcite Calcite Calcite Calcite Calcite Calcite Calcite -500 0 500 1000 1500 2000 2500 4 9 14 19 24 29 34 39 44 49 54 59 64 69 2 Theta degrees Counts Cuexcomate XRD Sinter A072 Calcite Tridimite Amorphous silica Punch Bowl Geyser, Yellowstone National Park Castle Geyser, Yellowstone National Park Fly Ranch Geyser, Nevada, US Taupo, New Zeland Castle Geyser, Yellowstone National Park Pool geyser Taupo, New Zeland Active geysers Inactive geysers Sinter deposits Hot pools and terraces 1100° C 500° C 400° C 300° C 200° C 0 km 1 2 Ascending Hot water 6 m 6 m 2 m 1 m Apaseo geyserite sinters