Volcanic Types & Emissions: Exploring Composite Volcanoes

Abstract

Course name Instructor’s name Assignment due date Science Writing Activity: Volcano Types & Emissions Volcanic eruptions lead to different types of volcanoes depending on the composition, viscosity, and the level of gas content of magma. Composite volcanoes or stratovolcanoes are defined by the type of eruption or eruptions and the resulting shape or structure that differs from other types of volcanoes. They have a layered structure resulting from repeated eruptions of trapped gases and lave released to the surface over long periods of time. They form some of the largest volcanoes often being more than 1000 feet and are towering structures with a small summit crater (Bennett, 2022). They have concave slopes that are steeper near the summit with a narrow base compared to the larger shield volcanoes. Composite volcanoes result from the formation of alternating layers of lava that may sometimes form from vents on the slopes of the main volcano. The type of lava determines the shape and the type of volcano formed after eruptions (Bennett, 2022). For the composite volcano, the lava is mostly andesite and rhyolitic which is cool and has large amounts of trapped gases. They are characterized by explosive eruptions as a result of the high pressure and the large amounts of trapped gases released during their formation. The chemistry of a volcano determines the type of eruption and the nature of magma and gases ejected during its formation. Composite volcanoes have magma that is rich in silica, viscous, and have high amounts of trapped gases released during the eruption. Andesite lava consists of 57.94% SiO2 and 17.02% Al2O3 while dacite lava has 65.01% SiO2 and 15.91% Al2O3 (Oregon State University, 2025). Composite volcanoes sometimes have high amounts of rhyolite lava that consists of...