Either in describing rocks or lava, mafic means that the lava or rock has less silica while felsic implies that the lava or rock has the most silica. 6. Mafic rocks are darker in color than felsic rocks.
What determines if a rock is felsic or mafic?
In a widely accepted silica-content classification scheme, rocks with more than 65 percent silica are called felsic; those with between 55 and 65 percent silica are intermediate; those with between 45 and 55 percent silica are mafic; and those with less than 45 percent are ultramafic.
What are the three differences between mafic and felsic rocks?
Mafic rocks are rich in iron and magnesium, whereas Felsic rocks are rich in silica and aluminum. Mafic rocks are denser and heavier than Felsic rocks. Mafic rocks are darker in color than Felsic rocks. Lava made up of Felsic rocks is slow moving and has a higher viscosity than Mafic lava.
What are the two main differences between mafic magma and felsic magma?
Mafic magmas are low in silica and contain more dark, magnesium and iron rich mafic minerals, such as olivine and pyroxene. Felsic magmas are higher in silica and contain lighter colored minerals such as quartz and orthoclase feldspar. The higher the amount of silica in the magma, the higher is its viscosity.
What is Phaneritic and Aphanitic?
APHANITIC TEXTURE – Igneous rocks that form on the earth’s surface have very fine-grained texture because the crystals are too small to see without magnification. PHANERITIC TEXTURE – Igneous rocks with large, visible crystals because the rock formed slowly in an underground magma chamber.
What does mafic mean?
Definition of mafic
: of, relating to, or being a group of usually dark-colored minerals rich in magnesium and iron.
What are the 4 types of igneous rocks?
As has already been described, igneous rocks are classified into four categories, based on either their chemistry or their mineral composition: felsic, intermediate, mafic, and ultramafic.
Is obsidian mafic or felsic?
Though obsidian is usually dark in color, similar to mafic rocks such as basalt, the composition of obsidian is extremely felsic.
What is the difference between mineralogy and crystallography?
The mineralogy has more scientific branches such as the following: 1. Crystallography studies crystal forms, i.e. forms in which the minerals crystallize, as well as their internal structure, relations and distribution of atoms, ions or ionic groups in the crystal lattice. 2.
Why are mafic rocks dense than felsic?
The mafic rocks also typically have a higher density than felsic rocks. The term roughly corresponds to the older basic rock class. Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma.
Is felsic light or dark?
Felsic minerals (quartz, K feldspar, etc) are light colored while mafic minerals (hornblende, pyroxenes) are normally dark colored. Felsic minerals have the lowest melting points (600 to 750 °C) and mafic minerals have higher melting points (1000 to 1200 °C).
Is mafic or felsic more explosive?
In general, the more felsic the magma the greater the volatile content. So mafic/basaltic volcanoes are fairly quiescent, intermediate/andesitic volcanic eruptions are moderately explosive, and felsic/rhyolitic volcanoes may be extremely explosive.
Why are felsic magmas more viscous?
First, as we’ve already discussed, felsic magmas tend to be more viscous because they have more silica, and hence more polymerization. Second, felsic magmas tend to have higher levels of volatiles; that is, components that behave as gases during volcanic eruptions.
Why are there different compositions of magma?
The composition of magma depends on the rock it was formed from (by melting), and the conditions of that melting. Magmas derived from the mantle have higher levels of iron, magnesium, and calcium, but they are still likely to be dominated by oxygen and silicon.
Is basalt mafic or felsic?
Granite and rhyolite are considered felsic, while basalt and gabbro are mafic (click here for more information on mafic and felsic). Felsic rocks, in general, form the bulk of the continental plates, while mafic basalt forms the seafloor.
What is aphanitic and pyroclastic texture?
There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic. Aphanitic (a = not, phaner = visible) rocks, in contrast to phaneritic rocks, typically form from lava which crystallize rapidly on or near Earth’s surface.
