Stratovulkaner

Stratovulkaner, or stratovolcanoes, are large, cone-shaped volcanoes formed from alternating layers of hardened lava flows, volcanic ash, pumice, and other tephra. The term reflects their layered construction, produced by cycles of explosive eruptions that eject ash and pumice, followed by quieter lava effusion that creates new lava flows. They are common at convergent plate boundaries where subduction drives magma formation.

Morphology and magma composition are key features. Stratovolcanoes typically have steep profiles and summit craters. The magma is usually viscous andesitic to rhyolitic, which traps gases and promotes explosive outbursts. Repeated eruptions accumulate layered deposits, sometimes with lava domes that grow within the crater.

Eruptive activity and hazards are diverse. Eruptions can alternate between explosive plumes and effusive lava flows. Pyroclastic flows, ash falls, and lahars pose significant risks to nearby populations and infrastructure. The combination of steep slopes and volatile magma makes these systems among the most hazardous in many volcanic arcs.

Formation and tectonics. Stratovolcanoes commonly form above subduction zones, where an oceanic plate dives beneath a continental or another oceanic plate. Subduction generates magma with higher silica content and dissolved gases, fueling both explosive and effusive eruptions and the buildup of layered volcanic structures.

Examples include Mount Fuji in Japan, Mount Vesuvius in Italy, Mount St. Helens in the United States, Mount Etna in Italy, Cotopaxi in Ecuador, and Merapi in Indonesia. They illustrate the global distribution and varied activity of this volcanic class.