Publication: Riesgos hidrovolcánicos en el volcán Fuego de Colima, México
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2016-02-10
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Universidad Complutense de Madrid
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Abstract
Los ambientes volcánicos son de por sí una de las zonas naturales más dinámicas y peligrosas del mundo, por lo que si se añaden factores extrínsecos a su naturaleza pueden convertirse en verdaderos focos de desastres. Las zonas volcánicas más activas del mundo se ubican en las zonas de subducción de algunas de las Placas tectónicas más dinámicas, pudiendo destacar el caso de Islandia, México o el Sudeste Asiático. Además, algunas de estas regiones ven agravada su situación debido a su ubicación dentro de zonas latitudinales con marcada estacionalidad, como la franja intertropical, donde las intensas y abundantes lluvias se concentran en apenas unos meses y generan procesos volcánicos secundarios, como es el caso de los lahares. El término lahar hace referencia al flujo formado por una mezcla de material volcánico y agua en diversa proporción, pudiendo abarcar tanto flujos de derrubios como flujos hiperconcentrados y corrientes más fluidas, que suelen canalizarse por los drenajes del edificio volcánico y alcanzar grandes distancias desde su origen. Precisamente la formación de estos flujos está supeditada a la disponibilidad de una fuente hídrica relevante para arrastrar el material volcánico, pudiendo proceder de lagos, cursos de agua, precipitación o deshielo de nieve o glaciares. Este trabajo se centra en la formación y caracterización de los lahares generados en el volcán más activo de la Placa Norteamericana, situado en México y denominado Volcán de Colima o Volcán de Fuego, y más concretamente en uno de sus drenajes por donde es frecuente la canalización de lahares, la barranca de Montegrande situada en la vertiente S del mismo. Para ello se aborda el problema de la ocurrencia de lahares desde diferentes puntos de vista. El primero de ellos es la descripción geográfica regional del mismo, ya que de ella depende en gran medida la dinámica lahárica de estudio. Entre los factores considerados destaca el análisis del contexto tectónico-estructural del volcán, la evolución de la actividad eruptiva, la caracterización geológica, geomorfológica y climática del área, así como su relación con la vegetación, la hidrología y los asentamientos humanos desde una perspectiva socioeconómica. A partir de la información anterior se profundiza en la caracterización de la barranca de interés en relación con la formación de lahares. Se recopila toda la información disponible de los eventos pasados que han sido registrados a lo largo de la historia, se caracterizan los depósitos generados, se describe la forma de obtención de los datos y en su caso la existencia de equipos de monitorización de los mismos, y por último se relaciona la formación de los lahares con la única fuente hídrica disponible en el Volcán de Colima para ello, la precipitación. Tras esto se intenta cuantificar la dinámica hidrometeorológica y erosiva que caracteriza a los lahares en Montegrande desde un punto de vista multidisciplinar, partiendo de todos los datos recopilados con anterioridad. La metodología empleada abarca desde análisis hidrometeorológicos clásicos a modelos numéricos de simulación, pasando por estimaciones volumétricas basadas en la comparación de perfiles topográficos del interior de la barranca, o el empleo de SIG (Sistemas de Información Geográfica). De forma complementaria al estudio anterior, los resultados del mismo se emplean para la simulación de algunos eventos pasados que se consideran representativos de la variabilidad de flujos que pueden llegar a darse en el Volcán de Colima. El modelo numérico que se usa para ello es SPH (Smoothed Particle Hydrodynamics o modelo Hidrodinámico de Partícula Suavizada).Previamente a su aplicación en el terreno se hace un análisis de sensibilidad de la influencia de ciertas condiciones iniciales y parámetros reológicos en la dinámica del flujo, que sirve de guía y base para el diseño de las simulaciones a realizar de los lahares reales. RESUMEN XXXII De esta manera, se obtiene una caracterización más precisa de los lahares en el Volcán de Colima que puede emplearse para la gestión del riesgo que suponen estos eventos en su entorno, así como un posible método de previsión de los mismos, verificado con la realidad.
Volcanic areas are one of the most dynamic and dangerous natural places in the world. Most active volcanic complexes are located at the subduction zones of tectonic Plates, as the case of Iceland, Mexico and Southeast Asia. Furthermore, some of these areas dare with secondary hydrovolcanic processes, due to their location within latitudinal zones with marked seasonality as the intertropical convergence zone (ITCZ). Volcán de Fuego (also called Colima volcano) is located at 10º 30’ 44” N, 103º 37’ 02” W, within the ITCZ and is considered the most active volcano in Mexico and the North American Plate. It is 3.860 m a.s.l. height, but also the youngest edifice of the N-S trending Colima Volcanic Complex (CVC) located in the western sector of the Trans-Mexican Volcanic Belt (TMVB), at the southern edge of the Colima Graben. The CVC is formed by three large andesitic stratovolcanoes, of which the Colima volcano is the only active at the present. Associated to its frequent volcanic activity, renovated in 1998, 2010, 2013 and later in 2015, secondary processes like lahars, triggered by rain mixing with the loose pyroclastic debris produced, are common. Colima lahars’ channel through strong slopes of the main water drainages (ravines) and reach large distances along their path (from 7 km to 15 km long) damaging all kind of human infrastructures and private property at the surrounding area, with catastrophic effects on the population (about 10,000 people) and their activities, as the 1955 lahar in the village of Atenquique where 23 people died. Most active ravines al the Colima volcano are located at the S-SW slopes, due to the orographic rains produced by the collide of oceanic humid air masses and the volcano. This study focuses on one of these southern active ravines called Montegrande, downstream of which the 8.600 inhabitants town of Quesería is located. The annual rainfall at the Montegrande ravine varies between 703 mm and 1,400 mm per year, concentrating the 95% of it during the rainy season that takes from June to October. Lahars seem to be more frequent just after main magmatic phases and gradually decreasing along the following years, but also during tropical storms rainfalls, as in 2011. Then active volcanism, rain and strong slopes are thought to be the main parameters that trigger lahars at the Colima volcano, so data about them is required in order to study their influence. To improve de knowledge of lahars, laharic activity in Montegrande ravine has been monitored with a main station installed at 2,100 m.a.s.l. This station counted with a visual recording camera, a HOBO rain gauge, a humidity sensor, a seismometer and 2 broadband geophones situated 500 m downstream of the seismometer, and 3 km of each other. This main station has been destroyed by a pyroclastic flow in July 2015. Several pressure sensors were installed at the Colima volcano, one of them at the Montegrande ravine, but 2011 lahars caused several damages and no data could be used. In view of the seriousness of the situation, it appears the urgent need to define and estimate the intensity of lahars, but also their modeling for the assess of the related hazard
Volcanic areas are one of the most dynamic and dangerous natural places in the world. Most active volcanic complexes are located at the subduction zones of tectonic Plates, as the case of Iceland, Mexico and Southeast Asia. Furthermore, some of these areas dare with secondary hydrovolcanic processes, due to their location within latitudinal zones with marked seasonality as the intertropical convergence zone (ITCZ). Volcán de Fuego (also called Colima volcano) is located at 10º 30’ 44” N, 103º 37’ 02” W, within the ITCZ and is considered the most active volcano in Mexico and the North American Plate. It is 3.860 m a.s.l. height, but also the youngest edifice of the N-S trending Colima Volcanic Complex (CVC) located in the western sector of the Trans-Mexican Volcanic Belt (TMVB), at the southern edge of the Colima Graben. The CVC is formed by three large andesitic stratovolcanoes, of which the Colima volcano is the only active at the present. Associated to its frequent volcanic activity, renovated in 1998, 2010, 2013 and later in 2015, secondary processes like lahars, triggered by rain mixing with the loose pyroclastic debris produced, are common. Colima lahars’ channel through strong slopes of the main water drainages (ravines) and reach large distances along their path (from 7 km to 15 km long) damaging all kind of human infrastructures and private property at the surrounding area, with catastrophic effects on the population (about 10,000 people) and their activities, as the 1955 lahar in the village of Atenquique where 23 people died. Most active ravines al the Colima volcano are located at the S-SW slopes, due to the orographic rains produced by the collide of oceanic humid air masses and the volcano. This study focuses on one of these southern active ravines called Montegrande, downstream of which the 8.600 inhabitants town of Quesería is located. The annual rainfall at the Montegrande ravine varies between 703 mm and 1,400 mm per year, concentrating the 95% of it during the rainy season that takes from June to October. Lahars seem to be more frequent just after main magmatic phases and gradually decreasing along the following years, but also during tropical storms rainfalls, as in 2011. Then active volcanism, rain and strong slopes are thought to be the main parameters that trigger lahars at the Colima volcano, so data about them is required in order to study their influence. To improve de knowledge of lahars, laharic activity in Montegrande ravine has been monitored with a main station installed at 2,100 m.a.s.l. This station counted with a visual recording camera, a HOBO rain gauge, a humidity sensor, a seismometer and 2 broadband geophones situated 500 m downstream of the seismometer, and 3 km of each other. This main station has been destroyed by a pyroclastic flow in July 2015. Several pressure sensors were installed at the Colima volcano, one of them at the Montegrande ravine, but 2011 lahars caused several damages and no data could be used. In view of the seriousness of the situation, it appears the urgent need to define and estimate the intensity of lahars, but also their modeling for the assess of the related hazard
Description
Tesis inédita de la Universidad Complutense de Madrid, Facultad de Geografía e Historia, leída el 14-12-2015