How does silica affect volcanic eruptions?
The silica content of the magma determines how thick the magma is, how easily it flows and how easily dissolved gases within the magma can escape; therefore the silica content determines the characteristic of the volcanic eruption and the shape and size of the resulting volcanic cone.
How does the silica content of magma affect how explosive an eruption is?
A more viscous (thick) magma will produce a more violent eruption This is controlled in part by the concentration of silica in the magma. A magma with low silica (<45%) will be runny and so the eruption will not be explosive. A magma with high silica (>60%) will be quite viscous and so the eruption will be violent.
How does Silicon effect magma composition and eruptions?
Magmas that have a high silica content will therefore exhibit greater degrees of polymerization, and have higher viscosities, than those with low-silica contents. The amount of dissolved gases in the magma can also affect it’s viscosity, but in a more ambiguous way than temperature and silica content.
How does silica content affect the viscosity of magma?
Explanation: Viscosity of magma, the resistance to flow depends on composition of the magma and temperature. Higher silica content means higher viscosity. But lower temperatures and low gas content mean higher viscosity.
What is silica in a volcano?
Silicon dioxide, the most abundant rock-forming compound on Earth and the predominant molecular constituent of volcanic rocks and magmas. It tends to polymerize into molecular chains, increasing the viscosity of the magma.
How does silica affect viscosity?
A magma’s silica content will not only control the rock type that forms, it also controls the relative viscosity of the magma. Differences in a magma’s viscosity will determine the shape a volcano takes. High-silica (basalt) magma has a much lower viscosity. It flows much easier and over longer distances.
Why does silica increase viscosity?
The cooler the lava, the higher the viscosity (the thicker it is). Composition: he more felsic the lava (the more silica in the lava), the higher the viscosity because silica forms chains in the cooling lava even before it crystallizes. The more mafic the lava (the less silica in it), the lower the viscosity.
Where do explosive silica rich volcanoes occur?
Most explosive eruptions occur in volcanoes above subduction zones, where one tectonic plate dives beneath the other. Eighty to 120 kilometers below the surface, magma forms when the rocks of the mantle melt just above the subducting plate.
What does silica rich magma mean?
Silicate-rich magmas are typically formed at destructive plate boundaries, by partial melting and/or assimilation of crustal rocks (which are richer in silica than the rock of the mantle). Such magmas erupt as andesites and rhyolites or are intruded as granite masses.
What factors affect the eruption style of a volcano?
The style of eruption depends on a number of factors, including the magma chemistry and content, temperature, viscosity, volume and how much water and gas is in it, the presence of groundwater, and the plumbing of the volcano. gases and lava.
What magma types produce explosive and effusive eruptions?
Effusive eruptions involve the outpouring of basaltic magma that is relatively low in viscosity and in gas content. Explosive eruptions generally involve magma that is more viscous and has a higher gas content. Such magma is often shattered into pyroclastic fragments by explosive gas expansion during an eruption.
What causes the eruption of the volcano?
Volcanoes erupt when molten rock called magma rises to the surface. Magma is formed when the earth’s mantle melts. Melting may happen where tectonic plates are pulling apart or where one plate is pushed down under another. Magma is lighter than rock so rises towards the Earth’s surface.
How does the amount of silica affect how magma flows?
The amount of silica effect how magma flows is very important. If a volcano has lots of silica, its eruption would be explosive and the magma would be chuncky and very sticky. It would be like peanut butter running down a plate. What are the two factors the control whether a volcano eruption will be explosive or quiet?
If a volcano’s magma is high in silica, the volcano will probably erupt explosively. If the magma is not high in silica, the volcano will probably erupt quietly.
How does the composition of magma affect the rate of eruption?
If the composition of the magma is low in silica, it will produce a quiet eruption. The eruption(s) of Mt. Kilauea are quiet eruptions.
What is the composition of magma that makes it explosive?
If the composition of the magma is high in silica, the eruption will be explosive. The Eruption of Mt. St. Helens was an explosive eruption.