As one might notice, mafic and felsic terms aren’t used often. These words are only known by geologists and those who study this field. What is it, you ask?
On chemical analysis, it was found that igneous rocks were rich in silicate oxides. Therefore, these rocks would be classified based on the amount of silica. They were then divided into four types, ultramafic (mafic), intermediate (felsic), according to the increasing amount of silica.
Mafic and felsic refer to the silica content in igneous rock formed by the cooling of lava. They are sometimes used to distinguish the characteristics of lava (or magma). They also have contrasting colors: Mafic is darker shades of green, while Felsic has lighter rocks.
Mafic Vs. Felsic
The silica content is what makes the difference between Mafic rocks and Felsic rock. Because igneous rocks are characterized by their silica content, mafic has a lower silica percentage (approx. 45-55%, while felsic has a higher silica content (approx.70-90%).
The appearance of the two igneous rock types is different. One has a darker shade, and the other has a lighter shade. The origin of the rocks is what causes the differences in silica levels.
What is Mafic?
Mafic, which stands for magnesium and iron (Latin: Iron), is an acronym that refers to igneous rocks rich in these minerals. Mafic lava usually reaches 950, which can lead to weak volcanic eruptions. It isn’t explosive nor violent.
Mafic rocks can be found in dark greens or greenish blacks. They are medium- to coarse-grained.
These rocks are low in density due to their low silica content. Because their source is mainly the seabed, which is low in silica, this is why they are so dense.
Because of the low viscosity, lava that has erupted is often very runny. Basalt is an example of mafic rock.
What is Felsic?
Felsic refers to the rock rich in mental feldspar that is high in aluminum and silica. Felsic lava can cause volcanic eruptions by being found between 650 and 750° C. These rocks also contain other minerals such as oxygen, potassium, and sodium. This is why felsic rocks have a low density.
Because of their geographical location, the felsic rock’s high silica content (70 to 85%) can be explained. These rocks are found mostly in convergent areas, which is where geologic plates meet. Because of the magma, the area has high levels of silica and water. This makes the lava sticky.
Graphite is a felsic rock.
Difference between Felsic And Mafic
The silica content in both felsic and mafic rocks is what makes them different. Low levels of silica are found in mafic. Only 45-55%. Basalt, which is a common example of Mafic rock, has a silica content of only 50%. Felsic, on the other hand, have much higher levels. Approximately 70-85%. Graphite contains 70% silica.
These rocks are formed from lavas that have been cooled. Mafic lava is usually low in viscosity, and it runs. These lavas are hot and erupt quickly. Felsic rocks, on the other hand, have high viscosity. This is because the temperature of lava is lower than that of mafic lava.
Both are igneous rocks and are distinguished by their silica levels. However, the origin of the rocks is determined by the silica content. Most mafic rocks come from seabed volcanoes, while felsic rocks are formed from cooling lavas in the convergent areas.
The minerals found in both rocks are different due to their origin. Mafic is rich in heavy minerals such as magnesium, iron, and ferric. Felsic, however, is rich in silica as well as aluminum.
Felsic also contains low-density minerals such as potassium, sodium, and oxygen. These rocks are lighter than the mafic rock, which has a high density and is heavy.
Because of the minerals in both, there is a contrast in their distinctive appearance. Mafic rocks can be dark green, greenish-black, or coarse-grained. However, felsic rocks have a smoother surface and are lighter-colored.
Conclusion
Both mafic and felsic igneous rock forms are formed from the cooling of volcanic eruptions’ lava. Two types of igneous rocks can be classified by the silica content: mafic or felsic. The other two categories are ultramafic or intermediate.
Mafic rocks have a silica content of 45-55%. This is due to the fact that they were formed in volcanic eruptions at the seabed. They are low in viscosity, high in density, and affected by high temperatures of the lava.
The silica content of felsic rocks ranges from 70 to 85%. This is due to their origin, the convergence zone. Their original locations, rich in silica and water, have given rise to high viscosity. Low density and lightweight are due to the presence of lightweight minerals like potassium, sodium, and oxygen.
Mafic rocks contain high levels of iron and magnesium. These rocks have a distinctive dark green to greenish-black color. Felsic rocks, on the other hand, are rich in silica, aluminum, and oxygen as well as sodium, potassium and provide a light shade.