How Does Silica Affect Viscosity?
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).Sep 14 2015
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. 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.
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.
Why is silica a big 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 silica content affect the viscosity of 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 increasing the silica content affect the viscosity of magma?
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).
What does it mean by higher silica content magma in terms of viscosity?
The higher the amount of silica in the magma the higher is its viscosity. Viscosity is a liquid’s resistance to flow. Viscosity determines what the magma will do. Mafic magma is not viscous and will flow easily to the surface. Felsic magma is viscous and does not flow easily.
What are the three factors that affect 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.
How does viscosity affects the movement of magma?
Heating reduces viscosity (warm syrup flows more easily than cold.) High viscosity lavas flow slowly and typically cover small areas. In contrast low viscosity magmas flow more rapidly and form lava flows that cover thousands of square kilometers.
Does low viscosity lava have low silica content?
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 silica get into magma?
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).
Why is silica in magma?
What role does silica play in eruptions?
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.
What is the relationship between silica content and 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.
Which of the following does not affect a magma viscosity?
Question: Which of the following does not affect the viscosity of magma? Temperature Silica Content Amount of gas None of these affects the viscosity of the magma.
Do gases escape more easily from high viscosity or low viscosity magma?
If the magma has a lower viscosity the gas bubbles will be able to escape from the magma more easily so the lava won’t erupt as violently. An effusive lava flow from Pu`u `O`o Cone on Kilauea Volcano in Hawaii.
Which type of magma most likely has the highest viscosity?
What is the difference in silica content and viscosity between light colored and dark colored magma?
The amount of silica in magma helps to determine its viscosity. The more silica magma contains the higher its viscosity. Magma that is high in silica produces light-colored lava that is too sticky to flow very far ex. … Low-silica magma flows readily and produces dark-colored lava ex.
Why does a higher temperature cause the viscosity of a magma to decrease?
As temperature increases viscosity decreases because the flow rate gets faster. The liquid does not resist movement when hot. VISCOSITY is directly related to the amount of silica (sand) in the magma. … The higher the water content as a liquid the lower the viscosity.
Magmas differ in composition which affects viscosity. Magma composition has a large effect on how a volcano erupts. Felsic lavas are more viscous and erupt explosively or do not erupt. Mafic lavas are less viscous and erupt effusively.
What does a low viscosity mean?
Viscosity is a measure of a fluid’s resistance to flow.
It describes the internal friction of a moving fluid. … A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion.
What are the factors that affect viscosity?
Viscosity is resistance to flow. For liquids typically the larger the intermolecular forces (IMF) the higher the viscosity. The other factors that affect viscosity are temperature and the shape of the molecule.
What are two primary factors that affect the viscosity of magma?
The viscosity of a magma is affected by its silica content and temperature. The amount of silica influences the magma’s viscosity in such a way that if the silica content is low the magma would have low viscosity whereas a high content of silica would make the magma more thick and sticky.
How does viscosity affect volcanoes?
Viscosity is the ability of a liquid to resist flowing. This means liquids with a higher viscosity are thicker and do not flow as easily. … 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.
What increases viscosity of magma?
The viscosity of magma increases with: high % silica and cooler temperatures. … Plutonic rocks are formed when magma cools deep in the crust without erupting. Magma that is very thick (viscous) is more likely to remain below the surface.
Is more silica more explosive?
Because it is more difficult for dissolved gas to escape from more viscous magma higher silica magmas generally erupt more explosively. …
Which type of magma has the highest silica content and viscosity the least silica content and viscosity?
Does lava have high viscosity?
What are the three factors that influence viscosity of a lava quizlet?
Three factors that affect magma viscosity are temperature composition and presence of dissolved gases.
What does high viscosity mean?
In layman’s terms viscosity defines a fluid’s resistance to flow. The higher the viscosity of a liquid the thicker it is and the greater the resistance to flow.
How does the silica content in magma affect the formation of surface landforms?
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.
Is silica rich magma explosive?
Silica-Rich Magma Traps Explosive Gases Magma with a high silica content also tends to cause explosive eruptions. H. Silica-rich magma has a stiff consistency so it flows slowly and tends to harden in a volcano’s vents. … If enough pressure builds up an explosive eruption takes place.
When magma has a high viscosity How is it most likely to erupt?
A high viscosity magma will flow more readily and easily than a low viscosity magma. Therefore the eruption will be fluid and passive. A high viscosity magma will flow more readily and easily than a low viscosity magma. Therefore the eruption will be explosive.
How much silica is in lava?
Felsic or silicic lavas have a silica content greater than 63%.
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