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how does silica content affect the viscosity of magma?

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How Does 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).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.

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 silica effect 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. … Gas readily escapes from the lava.

How does the amount of silicon dioxide affect the viscosity of magma?

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.

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.

How does the silica content of magma affect how explosive an eruption is?

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 happens as the relative amount of silica in a magma or lava increases?

Partial melting and incorporation of crustal rocks increase silica content to intermediate or felsic range. -Result is a viscous (sticky) magma that contain lots of volatiles that want to escape quickly – this tends to produce violent eruptions.

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.

What is the connection between the amount of silica in a melt and how viscous it is?

What is the connection between the amount of silica in a melt and how viscous it is? Silica forms strong bonds, so higher amounts of silica make for more viscous magma.

What is the silica content in a magma that has low viscosity?

BASALTIC magmas have a LOW SILICA content (45-55%) and referred to as MAFIC in composition. RHYOLITIC magma contains more than 65% SILICA and is referred to as FELSIC.

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.

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.

Which type of magma has the highest silica content and viscosity the least silica content and viscosity?

Felsic magma
Felsic magma has the highest silica content of all magma types, between 65-70%. As a result, felsic magma also has the highest gas content and viscosity, and lowest mean temperatures, between 650o and 800o Celsius (1202o and 1472o Fahrenheit).

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What is a silica content?

silica, also called silicon dioxide, compound of the two most abundant elements in Earth’s crust, silicon and oxygen, SiO2. The mass of Earth’s crust is 59 percent silica, the main constituent of more than 95 percent of the known rocks.

What type of magma has the lowest silica content?

Basaltic magma
Basaltic magma is mafic, has a low viscosity, a high temperature, and a low silica content.

How do silica and temperature 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. … Hence, lower viscosity and low gas content mean higher temperature of magma.

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.

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.

Do explosive volcanoes have high silica content?

So mafic/basaltic volcanoes are fairly quiescent, intermediate/andesitic volcanic eruptions are moderately explosive, and felsic/rhyolitic volcanoes may be extremely explosive. … Felsic lavas are not as hot, high in silica and volatiles, and have a high viscosity. They are thick and gooey and resist flowing.

How does viscosity of pyroclastic materials affect the flow of lava during volcanic eruptions?

Pyroclastic Material

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If the magma has high gas content and high viscosity, the gas will expand in an explosive fashion and break the liquid into clots that fly through the air and cool along their path through the atmosphere. Alternatively it blast out solid pieces of rock that once formed the volcanic edifice.

Does silica increase 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).

What makes magma less viscous?

Viscosity of Magmas

Lower temperature magmas have higher viscosity than higher temperature magmas (viscosity decreases with increasing temperature of the magma).

Which of the following increases the viscosity of magma?

Second, the crystallization temperature of a magma increases as the amount of dissolved water decreases, so degassing of a wet magma promotes the nucleation and growth of many small crystals and this increases the viscosity of the magma.

What factors control the viscosity of a melt?

Answer: Viscosity in a melt is controlled by its composition (specifically, silica content) and temperature. Temperature affects viscosity because heat causes chemical bonds to break more easily. Therefore, a hotter lava of a given composition is less viscous than a Page 2 cooler lava of the same composition.

How does the amount of silica affect the color of igneous rock?

The more silica you have in a rock, the paler it tends to be. Felsic rocks have high silica content, because they contain lots of quartz and another mineral called feldspar.

How magma composition affects the eruption of a volcano?

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 type of magma has a low viscosity low silica content and is created at divergent plate boundaries?

Basaltic magma
Shield volcanoes are found on divergent plate boundaries , where two plates move away from one another. Shield volcanoes have the following characteristics: Basaltic magma, which is high in temperature, very low on silica and with low gas content.

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What is the relationship between the viscosity of a magma and the ease with which its gases can escape?

Viscosity – resistance to flow of a lava determines how easily the gas escapes. The more viscous the lava and the greater the volume of gas trying to escape, the more violent the eruption will be. Viscosity is most affected by temperature and silica content.

Which type of magma most likely has the highest viscosity?

rhyolitic magma
The magma that has the highest viscosity is rhyolitic 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.

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.

Why does silica increase the viscosity of magma?

As the magma cools, more and more bonds are created, which eventually leads to the development of crystals within the liquid medium. … 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 magma viscosity influence the explosive potential?

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 low silica (<45%) will be runny and so the eruption will not be explosive.

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