Holocene effusive flank eruptions in Masaya caldera, Nicaragua

Abstract Five unknown Holocene flank eruptions from the Masaya caldera are reported here. These eruptions comprise basaltic lava flows emplaced in Masaya’s northern rift zone along the Cofradía fault zone, east of Managua City. The lava flows were defined as Mosintepe, Portillo, Gorgonia, Campuzano, and Martha units. Paleosol samples were collected below each lava flow, and radiocarbon AMS analyses were performed, yielding ages of 2250 ± 30, 1610 ± 30, 1600 ± 30, 1140 ± 30, and 790 ± 30 yrs BP, respectively. Calibrated age intervals are 285–229 cal BC for Mosintepe, 496–534 cal AD for Portillo, 496–535 cal AD for Gorgonia, 914–976 cal AD for Campuzano, and 1226–1268 cal AD for Martha; all stratigraphically consistent. These eruptions emitted magma bulk volumes between 0.02 and 0.51 km 3 , reaching up to 8 km from their eruptive vent and 13 km from Masaya’s polygenetic system summit crater. Their mineral paragenesis, and major and trace element geochemical fingerprint reveals a common volcanic provenance from the Masaya caldera due to lateral magma draining. This study demonstrates that basaltic lava flow flank eruptions are common in the Masaya caldera along its northern volcanic rift zone. Therefore, this information should be considered in future hazard and risk assessments.