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.
What is felsic lava made of?
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. Viscosity is a liquid’s resistance to flow. Viscosity determines what the magma will do.
Is felsic lava light or dark?
Felsic igneous rocks, as a whole rock, tend to have light colors or shades: white, pink, light brown, light gray. Mafic igneous rocks, on the whole, tend to be dark colored, commonly black or dark gray. Most mafic magma originates by melting of rocks in the mantle that are extremely rich in iron and magnesium.
Are lava domes mafic or felsic?
Felsic to intermediate lava characteristic textures:
When volatiles are absent, viscosity causes slow eruptions as lava domes (right)
What is felsic magma?
Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are usually light in color and have specific gravities less than 3.
What type of volcano has felsic lava?
Composite Volcanoes
They tend to be made of felsic to intermediate rock and the viscosity of the lava means that eruptions tend to be explosive. The viscous lava cannot travel far down the sides of the volcano before it solidifies, which creates the steep slopes of a composite volcano.
Why is felsic lava more explosive?
The chemical composition, or the elements that make up the magma, influences the viscosity of the magma, which in turn can make the eruption more or less explosive. Felsic magma has more silica and alumina content, which makes magma more viscous.
How is felsic magma formed?
It has been suggested that felsic magmas found at subduction-zone volcanoes are produced by mechanisms including fractional crystallization with or without crustal assimilation8, partial melting of the crust9,10, and partial melting of metasomatised silica-excess pyroxenite mantle11,12.
What is a felsic composition?
Felsic Minerals & Felsic Composition. The term felsic generally refers to rocks or magma that has a silica (SiO2 S i O 2 ) content greater than 63%. Additionally, felsic igneous rocks contain more than 75% felsic minerals which are high in silica content.
What does felsic stand for?
Felsic. In geology felsic refers to igneous rocks that are relatively rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron.
What type of lava is mafic?
Describes magma that contains lower amounts of silica and is generally less viscous and less gas-rich than silicic magma. Tends to erupt effusively, as lava flows. Includes andesites (57-63 percent SiO2), basaltic andesites (53-57 percent SiO2), and basalts (47-53 percent SiO2).
Is felsic intrusive or extrusive?
Rhyolite refers to the volcanic and felsic igneous rocks and granite refer to intrusive and felsic igneous rocks. Andesite and diorite likewise refer to extrusive and intrusive intermediate rocks (with dacite and granodiorite applying to those rocks with composition between felsic and intermediate).
Is felsic magma explosive?
Gases – At depth in the Earth nearly all magmas contain gas. Gas gives magmas their explosive character, because the gas expands as pressure is reduced. Felsic magmas usually have higher gas contents than mafic magmas.
What is a felsic dome?
Although felsic lavas are generally associated with explosive Plinian-type eruptions, they sometimes extrude at the surface as relatively cold, viscous lava domes. Vesiculation during eruption will deplete the magma in volatiles, thus depriving the magma of the very gases needed for a sustained eruption.
Where does felsic magma generally form?
A. Intermediate and felsic magmas form around convergent margins with a subduction zone. 3. these volcanic mountain chains often form arc shapes, because that is the shape produced when a flat plate (tectonic plate) intersects a sphere (Earth).
