How does silica affect the viscosity of magma?
Viscosity of Magmas Viscosity depends on primarily on the composition of the magma, and temperature. Higher SiO2 (silica) content magmas have higher viscosity than lower SiO2 content magmas (viscosity increases with increasing SiO2 concentration in the magma).
Does silica make magma more viscous?
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.
Does more silica increase 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.
What makes the magma viscosity high or low?
Not surprisingly, magmas formed by partial melting of mantle rocks are much hotter – well over 1200oC for some Hawaiian basalts – than is the case for crustally derived melts. Rhyolites may reach the surface at temperatures of less than 900oC, and so have much higher viscosity.
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.
What does it means by lower viscosity magma?
Low viscosity magmas allow gases to escape easily whereas gas pressures can build up in high viscosity magmas – resulting in violent eruptions. (Blowing through a straw, it's easier to get water to bubble than a milk shake)
Why does silica affect viscosity?
Why does silica content affect 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.
What does it mean by lower viscous magma?
Low viscosity magmas allow gases to escape easily whereas gas pressures can build up in high viscosity magmas – resulting in violent eruptions.
How does silica affect lava flow?
Lava with high silica content is thick and viscous and does not readily flow. Lava rises up toward the surface but is too thick to squeeze through the cracks and fissures in the Earth. As lava continues to rise upward, pressure continues to build.
What is the effect of viscosity when silica content is high?
Viscosity is the resistance to flow (opposite of fluidity). Viscosity depends on primarily on the composition of the magma, and temperature. Higher SiO2 (silica) content magmas have higher viscosity than lower SiO2 content magmas (viscosity increases with increasing SiO2 concentration in the magma).
How does temperature and silica content affect the viscosity of magma?
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. Hence, lower viscosity and low gas content mean higher temperature of magma.
Which magma has the highest viscosity?
The magma that has the highest viscosity is rhyolitic magma. One of the main reasons for the high viscosity in rhyolitic magma is that it contains a…
How is silica and viscosity related?
Magmas with a higher SiO2 content have a higher viscosity. Ultimately, the viscosity of a magma will determine the shape a volcano takes over continued eruptions. A magma's silica content will not only control the rock type that forms, it also controls the relative viscosity of the magma.
What is the effect of silica content to 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.
How are silica content and viscosity related?
Magmas with a higher SiO2 content have a higher viscosity. Ultimately, the viscosity of a magma will determine the shape a volcano takes over continued eruptions. A magma's silica content will not only control the rock type that forms, it also controls the relative viscosity of the magma.
What does low silica content mean?
Magma with low silica content is very fluid and easily erupts onto the surface through cracks and crevices at the surface. Over time the layers of lava build up a volcanic cone. Low silica volcanoes are characterized by "quiet" eruptions. Lava is able to easily flow out of the ground.