Why does silica affect lava flow?
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.
Does magma have high silica content?
The magma types vary from mafic magmas, which have relatively low silica and high Fe and Mg contents, to felsic magmas, which have relatively high silica and low Fe and Mg contents.
What happened of the magma with high silica content?
Magmas with high silica content have a high viscosity (resistance to flow) and are generally more explosive when eruptions occur. All magmas also contain some degree of trapped gasses (CO2 & H2O ). The more trapped gas the more violent the explosion.
What is the relationship between the silica content of magma and viscosity?
The higher the amount of silica in the magma the higher is its viscosity. Viscosity is a liquid’s resistance to flow.
Why does silica increase viscosity?
Temperature: The hotter the lava, the lower the viscosity (the thinner it is). 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.
What effect does silica have on 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.
How does silica affect viscosity?
Why does silica content increase the 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.
How does the silica content affect the behavior of the magma quizlet?
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 silica content affect the viscosity?
Higher silica content means higher viscosity. But lower temperatures and low gas content mean higher viscosity. Hence, lower viscosity and low gas content mean higher temperature of magma.
What is silica content in lava?
The silica content and the amount of gas in the lava determines how fluid the lava is and how easily it will flow. High silica content produces a thick viscous lava that does not flow easily. Low silica content produces a lava that is more fluid and flows more easily.
Why does silica make magma more viscous?
Basaltic magma, having lower SiO2, is fairly fluid, but with increasing contents of SiO2, andesite, dacite, and rhyolite magmas become progressively more viscous. Because it is more difficult for dissolved gas to escape from more viscous magma, higher silica magmas generally erupt more explosively.
What does silica do to magma?
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.
What is the relationship between silica content and magma viscosity quizlet?
Higher silica increases viscosity. Magmas that have a high silica content will therefore exhibit greater degrees of polymerization, and have higher viscosities, than those with low-silica contents.
How does silica content affect the escape of gas in magma quizlet?
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. One other factor is the amount of dissolved volatiles in the magma (chlorine gas, water and other gases).
What are the 3 factors affecting the viscosity of magma?
The three factors that influence the viscosity of a lava are temperature, the dissolved gases it contains, and its chemical composition.
Why is silica content so important?
It is the silica content that controls the viscosity of the magma, and hence the nature of the volcanism that is seen. The low levels of silica mean that Hawaiian magma has a low viscosity, which explains why we see lava readily cascading downslope, and being churned up in the air in great fire fountains.
Which type of magma has the greatest silica content?
Felsic magma has more silica and alumina content, which makes magma more viscous. Mafic magma has less silica content and more iron and magnesium in it.
What is a high silica content?
The term high silica can be used to describe any high-purity glass. However, for use in reinforced plastics, we shall define high silica as a high-purity glass of 95%-plus punty SiO2 produced by a leaching process.
How does silica content affect viscosity?
What is the effect of silica content on magma?
What effect does silica content have on magma? The higher the silica content of the magma, the more viscous the magma. The higher the viscosity of the magma, the more explosive the eruptions of the volcano tend to be.
What is the viscosity of magma?
The magma is described as ‘rhyolitic’, and is far more viscous due to its higher silica content. The effect of this viscosity is that flowing rivers of lava are not common.
What is the difference between rhyolitic and felsic magma?
At the other end of the spectrum we have magma that is formed from ‘felsic’ volcanic rock, which has a much higher silicon content. The magma is described as ‘rhyolitic’, and is far more viscous due to its higher silica content. The effect of this viscosity is that flowing rivers of lava are not common.
How are silicate-rich magmas formed?
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).