Abstract

Determining whether a volcano is a cinder cone or a composite volcano is important because its classification categorizes the magmatic system and associated volcanic hazards. The criteria of age and size of the volcano that are usually used for this assessment are inadequate for active, young volcanoes. Other criteria on which that determination can be based are magma production rates, cone morphology, and eruption style. Cerro Negro is an active, young, small basaltic volcano in northwestern Nicaragua that is similar to both cinder cones and composite volcanoes in many ways. It has had at least 22 historically documented eruptions since it first appeared in 1850; the most recent occurred in late 1995. The magma production rate for Cerro Negro (∼1.6 km3/k.y.) is of the same magnitude as those of a variety of composite volcanoes and an order of magnitude higher than the production rate for the Parícutin cinder cone region of the Trans-Mexican volcanic belt. Structurally, Cerro Negro's cone, is a composite of scoria and lavas cut by dikes around a dense volcanic core. Cerro Negro's shape has been more like a composite volcano than a cinder cone, except when infrequent sub-Plinian eruptions have altered the cone to make it look like a cinder cone. Comparisons of Cerro Negro to well-known, historically active cinder cones and young composite volcanoes show that it is best described as a young composite volcano. The future hazards posed by Cerro Negro are, therefore, not those associated with cinder cone eruptions, but the potentially more dangerous ones of composite volcanoes.

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