Question

Mafic lava tends to have low silica content. Based on this, which of the following statements about mafic lava is most likely true?
A. It contains fewer volatile gases.
B. It has higher viscosity.
C. It flows slowly.
D. It contains more volatile gases.

Answer 1

Answer:

A. It contains fewer volatile gases.

Explanation:

Mafic lava have a composition of about 45-55% silica with high amount of Fe, Mg, Ca.

The silica content is quite low compared to those of granitic magma whose silica content can reach up to about 60%.

What determines the viscosity of magma is basically the silica content of the magma and the temperature of the magma. Viscosity is the resistance to flow.

The higher the silica content, the lower the viscosity and the higher the amount of volatile gases. Such type of magma is the granitic magma. Granitic magma due to their viscosity flows slowly.

The lower the silica content, the higher the viscosity and the lesser the presence of volatile gases in them. Such an example is Mafic magma. Mafic magma flows very slowly with low amount of dissolved gases.

Answer 2

Answer:

A. It contains fewer volatile gases

Explanation:

The mafic lava is a lava type that has low viscosity. The reason for that is its composition, being very rich in magnesium and iron. Because this type of lava is low in viscosity, it is unable to contain the majority of the gases and water in it, as they find it relatively easy to ''escape'' from it. That results in much calmer eruptions of the volcanoes that produce mafic magma, with explosions almost never occurring, and even if they do they are very small.