Megafan formation driven by explosive volcanism and active tectonic processes in a humid tropical environment |
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| Authors: | Jorge P Galve Guillermo E Alvarado José Vicente Pérez‐Peña Mauricio M Mora Guillermo Booth‐Rea José Miguel Azañón |
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| Affiliation: | 1. Departamento de Geodinámica, Universidad de Granada, Granada, Spain;2. área de Amenazas y Auscultación Sísmica y Volcánica, ICE, San José, Costa Rica;3. Escuela Centroamericana de Geología, Universidad de Costa Rica, San Pedro de Montes de Oca, Costa Rica;4. Instituto Andaluz de Geofísica (CSIC‐Universidad de Granada), Granada, Spain;5. Instituto Andaluz de Ciencias de la Tierra (CSIC‐Universidad de Granada), Armilla, Spain |
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| Abstract: | Quaternary volcanism in the Central Cordillera of Costa Rica has created an orographic barrier that concentrates rainfall on its northern side. This humid climate produces weathered bedrock prone to landsliding. Ash fall from explosive eruptions kills the vegetation cover and intensifies erosion processes. These eruptions, hydrothermal activity and associated earthquakes destabilize the slopes of river valleys, and even the volcanic edifices, producing landslides and large debris avalanches. All these processes mobilize an extra sediment input that is deposited in the piedmont lowlands forming the Santa Clara megafan. The megafans described in the literature mainly grow according to climatic fluctuations; however, sedimentation in the Santa Clara megafan is also controlled by endogenic processes with longer recurrence periods. Analysis of this megafan provides new insight into the origin and evolution of these landforms. In volcanic regions, active volcanism should be considered when investigating the formation of some megafans. |
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