Stratovolcano

Mount Vesuvius, near the city of Naples in Italy, violently erupted in 79 AD. The last eruption of this stratovolcano occurred in March 1944

A stratovolcano, also known as a composite volcano,[1] 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 felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).[2]

Stratovolcanoes are sometimes called "composite volcanoes" because of their composite stratified structure built up from sequential outpourings of erupted materials. They are among the most common types of volcanoes, in contrast to the less common shield volcanoes. Two famous examples of stratovolcanoes are Krakatoa, known for its catastrophic eruption in 1883 and Vesuvius, whose eruption in AD79 caused destruction of Pompeii and Herculaneum in 79 AD. Both eruptions claimed thousands of lives. In modern times, Mount St. Helens and Mount Pinatubo have erupted catastrophically, with lesser losses of lives.

The possible existence of stratovolcanoes on other terrestrial bodies of the Solar System has not been conclusively demonstrated.[3] The one feasible exception are the existence of some isolated massifs on Mars, for example the Zephyria Tholus.[4]

Creation

Cross-section of subduction zone and associated stratovolcanoes

Stratovolcanoes are common at subduction zones, forming chains and clusters along plate tectonic boundaries where oceanic crust is drawn under continental crust (continental arc volcanism, e.g. Cascade Range, central Andes, Campania) or another oceanic plate (island arc volcanism, e.g. Japan, Philippines, Aleutian Islands). The magma forming stratovolcanoes rises when water trapped both in hydrated minerals and in the porous basalt rock of the upper oceanic crust is released into mantle rock of the asthenosphere above the sinking oceanic slab. The release of water from hydrated minerals is termed "dewatering", and occurs at specific pressures and temperatures for each mineral, as the plate descends to greater depths. The water freed from the rock lowers the melting point of the overlying mantle rock, which then undergoes partial melting and rises due to its lighter density relative to the surrounding mantle rock, and pools temporarily at the base of the lithosphere. The magma then rises through the crust, incorporating silica-rich crustal rock, leading to a final intermediate composition. When the magma nears the top surface, it pools in a magma chamber within the crust below the stratovolcano.

There, the relatively low pressure allows water and other volatiles (mainly CO2, SO2, Cl2, and H2O) dissolved in the magma to escape from solution, as occurs when a bottle of carbonated water is opened, releasing CO2. Once a critical volume of magma and gas accumulates, the plug (solidified blockage) of the volcanic vent is broken, leading to a sudden explosive eruption.[citation needed]

Other Languages
العربية: بركان طبقي
asturianu: Estratovolcán
azərbaycanca: Qarışıq vulkan
беларуская: Стратавулкан
беларуская (тарашкевіца)‎: Стратавулькан
български: Стратовулкан
català: Estratovolcà
čeština: Stratovulkán
Deutsch: Schichtvulkan
español: Estratovolcán
Esperanto: Stratovulkano
français: Stratovolcan
한국어: 성층 화산
hrvatski: Stratovulkan
Ilokano: Estratobulkan
Bahasa Indonesia: Gunung berapi kerucut
íslenska: Eldkeila
italiano: Stratovulcano
Kapampangan: Estratubulkan
Kreyòl ayisyen: Vòlkan konpozit
latviešu: Stratovulkāns
lietuvių: Stratovulkanas
македонски: Стратовулкан
მარგალური: სტრატოვულკანი
Bahasa Melayu: Stratovolkano
Nederlands: Stratovulkaan
日本語: 成層火山
norsk nynorsk: Stratovulkan
occitan: Estratovolcan
polski: Stratowulkan
português: Estratovulcão
română: Stratovulcan
русиньскый: Стратовулкан
русский: Стратовулкан
Simple English: Stratovolcano
slovenčina: Stratovulkán
slovenščina: Stratovulkan
српски / srpski: Стратовулкан
srpskohrvatski / српскохрватски: Stratovulkan
svenska: Stratovulkan
Türkçe: Stratovolkan
українська: Стратовулкан
Tiếng Việt: Núi lửa dạng tầng
中文: 複式火山