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Some have collapsed summit craters called calderas. [3] The lava flowing from stratovolcanoes typically cools and solidifies 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 ...
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. The process that forms volcanoes is called volcanism. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth ...
Types of volcanic eruptions. Some of the eruptive structures formed during volcanic activity (counterclockwise): a Plinian eruption column, Hawaiian pahoehoe flows, and a lava arc from a Strombolian eruption. Several types of volcanic eruptions —during which material is expelled from a volcanic vent or fissure —have been distinguished by ...
Igneous rock (igneous from Latin igneus 'fiery'), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet 's mantle or crust.
Mount Semeru and Mount Bromo in East Java. Together, they form the Bromo Tengger Semeru National Park. Mount Agung and Mount Batur in Bali. Galunggung in West Java. Krakatoa. A violent eruption in August 1883 resulted in the obliteration of the three-peaked volcanic island. Anak Krakatoa.
Igneous differentiation. In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of (usually increasingly silicic) magmas produced by igneous differentiation is ...
Tephra is any sized or composition pyroclastic material produced by an explosive volcanic eruption and precise geological definitions exist. [2] It consists of a variety of materials, typically glassy particles formed by the cooling of droplets of magma, which may be vesicular, solid or flake-like, and a varying proportions of crystalline and ...
Cinder cone. A cinder cone (or scoria cone[1]) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. [2][3] The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent.