Stratovolcano Stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica (as in rhyolite, dacite, or andesite), with lesser amounts of less-viscous mafic magma. Extensive
Geology of Nicaragua Geology of Nicaragua The geology of Nicaragua includes Paleozoic crystalline basement rocks, Mesozoic intrusive igneous rocks and sedimentary rocks spanning the Cretaceous to the Pleistocene. Volcanoes erupted in the Paleogeneand within the last 2.5 million years of the Quaternary, due to the subduction of the Cocos Plate, which drives melting and magma creation. Many of these volcanoes are in the Nicaraguan Depression paralleled by the northwest-trending Middle America Trench which marks the Caribbean-Cocos plate boundary. Almost all the rocks in Nicaragua originated as dominantly felsic continental crust, unlike other areas in the region which include stranded sections of mafic oceanic