The 2005 eruption of Ilamatepec (Santa Ana) volcano,El Salvador |
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| Authors: | Teresa Scolamacchia Carlos Pullinger Lizeth Caballero Francisco Montalvo Laura E Beramendi Orosco Galia Gonzalez Hernández |
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| Institution: | 1. Dpto. de Ingeniería Topográfica y Cartografía, Universidad Politécnica de Madrid, Madrid, Spain;2. Departamento de Geodinámica, Universidad Complutense de Madrid, Madrid, Spain;3. IGEO, Instituto de Geociencias, UCM–CSIC, Madrid, Spain;4. CEI Campus Moncloa, UCM–UPM, Madrid, Spain;5. Gerencia de Geología, Dirección General del Observatorio Ambiental, Ministerio de Medio Ambiente y Recursos Naturales, El Salvador;1. Center for Volcanology and Geological Hazard Mitigation, Jl Diponegoro No57, Bandung, Indonesia;2. Laboratoire Magmas et Volcans, Université Blaise Pascal - CNRS - IRD, OPGC, 5 rue Kessler, 63038 Clermont Ferrand, France;3. Institut de Physique du Globe de Paris, Sorbonne Paris-Cité, Univ. Paris Diderot CNRS, F-75005 Paris, France;4. Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7193, ISTeP, F-75005, Paris, France;5. Earth & Life Institute, Universite´ catholique de Louvain, Croix du Sud, 2 bte L7.05.10, B-1348 Louvain-la-Neuve, Belgium;6. PPME, University of New Caledonia, BP R4, Avenue James Cook, 98851 Noumea, New Caledonia;7. LEGOS/MIO, IRD, 98800 Noumea, New Caledonia;8. Vanuatu Geohazards Observatory Port Vila, Vanuatu;9. Geological Survey of Japan, AIST, Tsukuba, Japan;10. IRD Centre de Noumea, 101 Promenade Roger Laroque, BP A5 - 98848 Noumea cedex, New Caledonia;1. INGV — Istituto Nazionale di Geofisica e Vulcanologia sez. Roma 1, Rome, Italy;2. INGV — Istituto Nazionale di Geofisica e Vulcanologia sez. Palermo, Palermo, Italy;3. Dipartimento di Scienze, University of Roma Tre, Rome, Italy;1. Laboratoire Magmas et Volcans, Clermont Université, Université Blaise Pascal, CNRS UMR 6524, IRD R 163, 5 rue Kessler, 63038 Clermont-Ferrand Cedex, France;2. Observatoire de Physique du Globe de Clermont-Ferrand, 24 avenue des Landais, BP 80026, 63171 Aubière Cedex, France;3. Departamento de Geología, Universidad de Atacama, Av. Copayapu 485, Copiapó, Chile;4. Departamento de Ciencias Geológicas, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile |
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| Abstract: | We report the stratigraphic sequence of the 2005 eruption of Ilamatepec volcano together with sedimentological and chemical analyses of its products.Structural and textural characteristics of the deposits indicate that the eruption was driven by a small-volume rhyolitic intrusion at shallow levels, which resulted first in the collapse of the existing hydrothermally altered fan of previous deposits inside the crater lake, driving phreatic explosions with launching of blocks on ballistic trajectories; later the magma interacted with lake waters producing several hydromagmatic pyroclastic density currents (PDCs). These flows were energetic enough to knock down pine trees up to distances of 1.8 km from the crater in the E-NE sector of the volcano. Finally, ejection of ballistic blocks that landed on previously emplaced, wet pyroclastic density current deposits, caused the generation of a lahar that flowed down the steep eastern flank toward the El Jabillal gully. Subsequent lahars occurred as a result of intense rain caused by hurricane Stan.Radiocarbon ages on paleosols and charcoal fragments, separating previous volcanogenic sequences, indicate that similar eruptions have occurred more frequently in the past centuries, than previously thought.The new data confirms that Ilamatepec volcano is one of the most active volcanoes in El Salvador. Nevertheless, more detailed studies of the eruptive sequence of Ilamatepec volcano are mandatory to establish future eruptive patterns. |
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