What has the biggest effect on the viscosity of lava?

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 increases the viscosity of lava?

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).

What are the two major factors that affect viscosity?

Those are:

• Fluid Temperature: Usually the viscosity of liquids decreases with an increase in temperature. …
• Flow Conditions: For laminar flow the viscosity of liquid remains constant while for turbulent flow viscosity changes.
• Pressure: With an increase in pressure, the viscosity of gases usually increase.

Which conditions can affect viscosity of magma or lava?

Three factors that affect magma viscosity are temperature, composition, and presence of dissolved gases.

What would magma with the highest viscosity contain?

Granitic magma is thick and stiff and contains lots of silica and dissolved gasses. Granitic magma has the most silica and has the highest viscosity.

How does the viscosity of lava affect volcanic eruption?

The viscosity of the magma, however, is also an important factor in determining whether an eruption will be explosive or nonexplosive. A low-viscosity magma, like basalt, will allow the escaping gases to migrate rapidly through the magma and escape to the surface.

Why does viscosity of lava vary between volcanoes?

Magmas that are more rhyolitic have a higher gas content. This gas content and relative viscosity leads to the more explosive and violent eruptions that occur at composite volcanoes. In general, SiO2 content controls the relative viscosity of a magma. Viscosity is the ability of a liquid to resist flowing.

How viscosity affect 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.

How does the viscosity of a lava affect the steepness of a volcano slope?

The low viscosity of the magma allows the lava to travel down slope on a gentle slope, but as it cools and its viscosity increases, its thickness builds up on the lower slopes giving a somewhat steeper lower slope. Most shield volcanoes have a roughly circular or oval shape in map view.

Which lava is more viscous?

rhyolitic lava

The most viscous lava is cool, high-silica lava called rhyolitic lava. This lava contains about 65-75% silicate and erupts at a temperature of about 650-800 degrees Celsius. Flows of this type of lava don’t move far from the vent, creating piles of solidified magma.

How does the viscosity of lava affect the formation of rocks?

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. Most felsic magma will stay deeper in the crust and will cool to form igneous intrusive rocks such as granite and granodiorite.

Which lava flow has low viscosity?

basaltic lava flow

Basalt has a SiO₂ content of ≤ 52% and contains relatively more magnesium and iron than more silicic igneous rocks. A basaltic lava flow has a low viscosity due to its low SiO₂ content. Eruptions associated with basaltic lava usually are not explosive due to the low silica and gas content.

Which type of magma has the highest 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 650^o and 800^o Celsius (1202^o and 1472^o Fahrenheit).

What does it mean by higher silica content magma in terms of viscosity?

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.

What is the viscosity of andesitic magma?

102 to 107 Pa s

Andesitic magmas, in particular, have a wide range of magma viscosities, from 102 to 107 Pa s, which is due to a wide range in phenocryst contents from 0 (phenocryst‐free andesitic melt) to ∼50 vol % (50 vol % rhyolitic melt + 50 vol % phenocrysts).

Why is andesitic lava viscous?

Andesitic lava is an example of a high viscosity lava whereas balastic lava has a low viscosity, so is more runny. High silica content in the andesitic lava contributes to causing this high viscosity and low silica content in the basaltic lava means it is of a lower viscosity.

How does the viscosity of magma change as magma cools?

How does the viscosity of magma change as magma cools? The viscosity increases when temperature decreases.

Which of the following lava compositions has the greatest amount of viscosity?

The magma that has the highest viscosity is rhyolitic magma.

How does the viscosity of the magma fed to volcanoes affect nearby life and property?

How does the viscosity of the magma fed to volcanoes affect nearby life and property? A volcano that expels highly viscous magma is a greater threat to life and property because it is more explosive and thus is more difficult or impossible to predict.

Where is the greatest volume of magma produced?

The greatest volume of magma is produced along the oceanic ridge system in association with seafloor spreading. As rock rises, it experiences a decrease in confining pressure and undergoes melting without the addition of heat.

Which statement describes the composition and viscosity of the lava associated with shield volcanoes?

Which statement describes the composition and viscosity of the lava associated with shield volcanoes? Lava from shield volcanoes is mafic and has a low viscosity.

Which of the following would decrease the viscosity of magma quizlet?

Which of the following would decrease the viscosity of magma? The more the silica in magma, the lower the viscosity.

How does the composition temperature and viscosity of lava differ between composite volcanoes and shield volcanoes?

How does the composition and viscosity of lava flows differ between composite volcanoes and shield volcanoes? Composite volcanoes tend to have intermediate to felsic lava that is very viscous whereas shield volcanoes have basaltic lava that is low in viscosity.

What three factors affect the explosive potential of a magma body beneath a volcano?

Temperature of magma, amount of dissolved gas in High viscosity and dissolved gas increase the explosive potential of a magma.

Which does not affect the viscosity of the magma?

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.

How does magma influences the explosiveness of an eruption?

For example, small crystals in the magma help gases escape. More crystals in the magma enable more gas bubbles to form, and so they make an eruption more explosive. The rate at which pressure is reduced also affects the explosiveness.