The Las Cañadas caldera wall and the outer slopes of the caldera provide three-dimensional exposures of numerous proximal-welded fallout deposits and have been mapped in detail. As a result, some parts of the Ucanca and Guajara Formations of the stratigraphy of Martí et al. (1994) have been divided into members that correspond to individual eruptions. Mapping has also revealed the occurrence of conduit-vent structures associated with proximal-welded fallout deposits. Conduit-vent structures consist of an upper flaring area and a lower narrow conduit. Conduit-vent geometry and dimensions include cylindrical plugs and eruptive fissures steeply dipping towards the caldera depression and elongated vents. The flaring area can be rather asymmetric and is usually filled by down-vent rheomorphic flow of the proximal fallout deposit. The lower conduits are filled by lava plug, agglutination of juveniles onto conduit walls and dyke intrusion with eventual dome extrusion. The eruption dynamics of welded fallout deposits and magma fragmentation within the conduit are consistent with an evolution from explosive to effusive. In this context conduit flow regimes evolve from turbulent to annular flow in which the conduit is progressively choked, and laminar flow leading to the final conduit closure.
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Carles Soriano is grateful for a Reincorporació de Doctors (RED) contract during this research. Comments by Sivia Zafrilla are fully acknowledged. This work was supported by the Ministerio de Ciencia y Tecnología (MCYT) projects REN2001-0502/RIESG and BTE2003-08026. We thank Instituto para la Conservación de la Naturaleza (ICONA) for permission to undertake this research. This paper has benefit from critical reviews by Bill Bonnichsen, Mike Branney and Raffaello Cioni.
Editorial responsibility: R. Cioni
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Soriano, C., Galindo, I., Martí, J. et al. Conduit-vent structures and related proximal deposits in the Las Cañadas caldera, Tenerife, Canary Islands. Bull Volcanol 69, 217–231 (2006). https://doi.org/10.1007/s00445-006-0069-2
- Welded fallout
- Conduit filling