ABSTRACT
Since the elegant summary of Central American geology by Weyl [1] in 1980, petrological and geochemical studies unveiled large variations in the Tertiary and Quaternary volcanics both along the volcanic chain and across it. The active volcanoes define an abrupt volcanic front, located 165 to 190 km inland from the Middle America trench (MAT). The front consists of 39 distinct centers or clusters of vents that occur in 100 to 300 km long lineaments or segments. Most of the active volcanic centers are complexes constructed primarily of basaltic to andesitic lavas. Several centers include calderas that erupted extensive silicic fall and flow deposits. Throughout most of Central America, the active volcanoes lie on the trenchward side of an extensive plateau of Tertiary volcanics, comprising primarily voluminous ignimbrite sheets that dominate the Tertiary topography. Mafic composite volcanoes, the predecessors of the active volcanic front, are recognizable in many areas and should ultimately be useful for defining the past positions of the volcanic front. Relatively few studies of the Tertiary volcanics have expanded the stratigraphic and petrologic knowledge base since Weyl’s review in 1980.
