Abstract
Geophysical and geological observations collected in 2007-2012 shed light on the mechanisms controlling the style and location of eruptions within the Las Sierras-Masaya Caldera complex, Nicaragua. These results confirm a hypothesised ~3.5 km diameter structure with features compatible with the presence of a ring fracture (50-65°, with inward-dipping bounding walls). A central block is bound by this fracture and defines an incipient nested caldera related to the emptying of the magma chamber following the last Plinian eruption (1.8 ka). The prolongation of the Cofradías fault from the Managua graben represents the most significant structure on the floor of Masaya caldera. Current activity, including a convecting lava lake, largely depends on the interplay between the extensional stress regime associated with the Managua graben and deformation along the inner caldera bounding fault. This high spatial resolution survey uses a novel combination of geophysical methodologies to identify previously overlooked foci for future volcanic activity at Masaya.
Highlights
Masaya volcano is one of the best-known volcanic edifices within the Nicaraguan volcanic chain due to its accessibility and relatively non-hazardous persistent activity
The importance of Masaya caldera derives from the fact that it is located less than 15 km from Managua, the capital and largest city in Nicaragua (>1,142,000 inhabitants, 2005 census), and one of the most populated
Caldera classification is challenging in this environment, but we suggest that it is most similar to a trap-door type [Cole et al 2005]
Summary
Masaya volcano is one of the best-known volcanic edifices within the Nicaraguan volcanic chain due to its accessibility and relatively non-hazardous persistent activity This basaltic caldera has been the source of three basaltic tephras over the last 6000 years, produced by highly explosive eruptions that have spread pyroclastic deposits over a large area of Western Nicaragua [Williams 1983a; Pérez and Freundt 2006; Kutterolf et al 2008; Pérez et al 2009]. There are a number of other important volcanic centres on the caldera floor, some of which have been named Most of these are distributed along suspected or inferred structures, such as a semi-circular feature in the north-western half of the caldera, faults geometrically related to the Cofradías fault of the Managua graben and others. A shallow lake fills the easternmost side of the caldera, bordering the city of Masaya
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