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Diapositiva 1 Gerardo Carrasco Centro de Geociencias, UNAM, México Geoscience Information for teachers European geosciences Union Mérida, oct. 2016 Zona de fusión Núcleo l 1,300 volcanes activos en los últimos 10,000 años l 600 volcanes activos en tiempos históricos l 50 volcanes hacen erupción cada año l 300,000 muertes desde el año 1,000 DC l 750 muertes por año l 92,000 (Volcán Tambora, Indonesia, 1815) PELIGROS VOLCÁNICOS LOS MAS CONOCIDOS – Flujos de lava – Caída de ceniza LOS MAS PELIGROSOS – Flujos piroclásticos – Lahares (flujos de lodo) – Avalanchas de escombros – TSUNAMIS FLUJOS DE LAVA CAÍDA DE CENIZA FLUJOS PIROCLÁSTICOS MT UNZEN, JAPÓN FLUJOS DE LODO (LAHARES) AVALANCHAS VOLCÁNICAS Mt Santa Helena 1980 TSUNAMIS Yellowstone-punto caliente CALDERAS- 10-80 km Su reactivación podría destruir Mas de 2/3 partes de EUA • SO2+H2O--- acid aerosols --- refleja luz solar • Enfriamiento terrestre • FotosíntesisX - interrupción cadena alimenticia • Extinción de especies Todas las extinciones masivas coinciden con grandes provincias ígneas • Inyección aerosoles a la estratósfera • Enfriamiento mayor a 10oC por varios años • Glaciación severa- nivel mar 100 m abajo • Migración, adaptación social • Hambre y muerte humana Reducción población a 10 mil HAMBRE POST-ERUPCION Tambora Tambora St. Pierre. Martinica (Antillas menores) Dionisio Pulido La gente migró a otros sitios Algunos imaginaban el fin del mundo Ni siquiera se sabía que era un volcán ANTES DESPUÉS Mexican Volcanic Belt Gulf of Mexico Los Humeros caldera 20° México City Serdán-Oriental Cofre de Perote- Basin Citlaltépetl range18 ° M E X I C O 100 km Activ e volcano Pliocene volca no P ac Miocene Volcano ifi c O c Caldera ea 105° n 101° 97° Mio cene-Pliocene Pliocene-Holocene Volcanic Arc Volcanic Arc Caldera de Mexican Volcanic Belt El Volcanillo Los Humeros Eastern Sector Cerro Pizarro Cofre de Perote maars rhyolitic domes La Gloria complex - Pico- Serdán- Cinder cones Oriental Cofre Las Cumbres maars basin range bimodal andesitic monogenetic Citlaltépetl poligenetic cinder cones volcanism volcanism 20 19.9 Teziutlán Zaragoza 19.8 Sierra Tlaxco Altotonga Los Potreros caldera r 19.7 e Los Humeros iv r o c 0 l u caldera0 p 5 A 2 19.6 Cuyoaco Las Aguilas IN S Perote Cofre de Cerro Grande A Perote 19.5 B Libres Cerro Pinto L A 19.4 T Oriental N IE N R 19.3 O N Las Derrumbadas 0 10 km Á 19.2 D R E Las Cumbres S 19.1 Citlaltépetl Cd. Serdán 19 -98 -97.9 -97.8 -97.7 -97.6 -97.5 -97.4 -97.3 -97.2 -97.1 -97 Cerro Pizarro A Pleistocene isolated rhyolitic dome regarded as a monogenetic extinct volcano A. Vitrophire 200 ky pyroclastic dome deposits lava flow pre-Cerro Pizarro volcanic and sedimentary substrate B. debris-avalanche deposits vitrophyre c in d e r c o n e cryptodome 180 ky pyroclastic deposits scoria cone lava flow pre-Cerro Pizarro volcanic and sedimentary substrate C. vitrophyre 116 ky Dome pyroclastic deposits rebuilt scoria cone lava flow pre-Cerro Pizarro volcanic and sedimentary substrate D. young pyroclastic deposits 65 ky vitrophyre pyroclastic deposits scoria cone lava flow (Riggs & Carrasco-Núñez,pre-Cerro Pizarro 2004; volcanic and sedimentary Carrasco substrate -Núñez & Riggs, 2007) Summit dome cryptodome (116 ky) Rhyolitic dome with a vithopyric Tilted basalts carapace (180 ky) (200 ky) Sector collapse scarp Rhyolitic dome with a vithopyric carapace (180 ky) Hummocky topography buried by pyroclastics Final pyroclastics (65 ky) a precolumbian (900 yr B.P.) twin-paired cone erupted contemporaneous lavas of contrasting composition RIO NAOLINCO Calc-alkaline basalt ~ 1km TOXTLACUAYA Hawaiite El Volcancillo Twin paired cone 2980 +- 55 yr B.P. < 900 yr B.P. 900 +- 50 yr B.P. 40,060 +- 2600 yr B.P. Siebert & Carrasco-Núñez, 2002 (JVGR 115, 179-205) El Volcancillo erupted 2 contrasting lava types Flow name Toxtlacuaya Río Naolinco Rock type Hawaiite & mugearite calci-alkaline basalt Lava type aa lava pahoehoe lava Effusion rate high low Duration short (hours) long (d-m-yrs) Volume small large # eruptions single (discrete) eruptive succession Cofre de Perote: a compound shield-like volcano Inactive since 200 kyr BP No magmatic multiple sector collapses (40 ky & 13 ky B.P.) Carrasco-Núñez et al. (2010) CVM Oriental Sector Jamapa Citlaltépetl Metlac Teteltzingo CONCLUSIONS Los Humeros- a nested caldera complex - active geothermal system since 0.5 Ma - must recent activity is younger than 20 kyr B.P which includes both: - effusive activity (basaltic lava flows) - explosive activity (Plinian fall) El Volcancillo- a small twin-paired cone - erupted 900 years ago. - it forms an active tectonic alignment which can be reactivated anytime. Therefore, even a reactivation of El Volcancillo is not likely, a new volcano can be formed along that structural system CONCLUSIONS . Cerro Pizarro- relatively small rhyolitic dome showing a complex evolution: alterated explosive-effusive activity, cryptosome intrusion, sector collapse, long repose with reactivation after 100 ky, compositional variations with time Therefore; behaves as a poligenetic volcano with a potential of reactivation in the future. Cofre de Perote- an inactive compound-shield like volcano where multiple sector collapses had occurred in Late Pleistocene-Holocene times posing an important hazard in the future. Apparent extint volcanoes must be investigated in detail to assess possible hazards in the future gracias .
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