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Source: Volcano World http://volcano.oregonstate.edu/volcano-factoids Silica: Influences lava viscosity and overall shape of the volcano. Silica molecules form a strong bond that permits entrapment of volcanic gases and promotes explosive volcanic eruptions. Low-silican magmas allow rapid escape of gases and low-explosivity eruptions.
The superheated magma rises through the mantle (yellow), melts the crust above (brown) and flows on to the surface forming a volcano. Typically, hotspot volcanoes are formed with ‘runny’ lava and have a flatter, less cone-like, profile and are called shield volcanoes.
22 Αυγ 2024 · The more silica, the more polymerization (formation of long molecules) happens, stiffening the lava. The stiffness of lava is described in terms of viscosity: lava that flows easily has low viscosity, and lava that is sticky and stiff has high viscosity.
This magma tends to be extremely viscous because of its high silica content, so it often does not reach the surface but cools and solidifies at depth. When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called volcanic arcs.
One key to what makes the eruption unique is the chemical composition of the magma that feeds a volcano, which determines (1) the eruption style, (2) the type of volcanic cone that forms, and (3) the composition of rocks that are found at the volcano.
One key to what makes the eruption unique is the chemical composition of the magma that feeds a volcano, which determines (1) the eruption style, (2) the type of volcanic cone that forms, and (3) the composition of rocks that are found at the volcano.
Where a volcano produces low viscosity, runny lava, it spreads far from the source and forms a volcano with gentle slopes: a shield volcano. Most shield volcanoes are formed from fluid, basaltic lava flows.
