Viscosity is the resistance to flow (opposite of fluidity). Viscosity depends on primarily on the composition of the magma,
and temperature
. Higher SiO
2
(silica) content magmas have higher viscosity than lower SiO
2
content magmas (viscosity increases with increasing SiO
2
concentration in the magma).
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. … When gases begin to escape (exsolve) from the magma, the effect of gas bubbles on the bulk viscosity is variable.
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 do silica content and temperature affect magma viscosity?
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.
What effect does the amount of silica have on 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 viscosity quizlet?
As
silica content increases, viscosity increases
. The magma slows down. WATER CONTENT is inversely related to viscosity. The higher the water content, as a liquid, the lower the viscosity.
What happens to the viscosity as the amount of silica increases?
Viscosity is the resistance to flow (opposite of fluidity). … Higher SiO
2
(silica) content magmas have higher viscosity than lower SiO
2
content magmas
(viscosity increases with increasing SiO
2
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.
Which type of magma has the greatest silica content?
- As a result of its higher viscosity and gas content, intermediate magma builds up pressure below the Earth’s surface before it can be released as lava.
- Felsic magma has the highest silica content of all magma types, between 65-70%.
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
.
What type of magma has the lowest silica content highest silica content?
Because
basalt
contains the least amount of silica and erupts at the highest temperature compared to the other types of lava, it has the lowest viscosity (the least resistance to flow). Thus, basalt lava moves over the ground easily, even down gentle slopes.
How does the amount of silica affect 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.
Why do some volcanoes have more silica?
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 type of magma has the highest silica content quizlet?
RHYOLITIC magma
contains more than 65% SILICA and is referred to as FELSIC. ANDESITIC magma is INTERMEDIATE in composition (55-65% SILICA).
What does silica have the greatest effect on?
5. Which of the two variables (SiO2 or H2O) seems to have the greatest effect on
eruption
? The silica content seems to have a greater effect than does the water content.
What is the relationship between viscosity and temperature quizlet?
VISCOSITY is inversely related to temperature
. As temperature increases, viscosity decreases because the flow rate gets faster. The liquid does not resist movement when hot.
