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 is the difference between felsic and mafic 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.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 mafic magma?
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 magma hot?
These types of lava are composed of aluminum, silica, potassium, sodium, calcium, and liquid quartz and feldspar. Felsic lava normally erupts between 650° C to 750° C. … This is one of the hottest types of lava coming out at temperatures exceed 950 degrees Celsius.
Where is felsic magma formed?
subduction zone
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).What is felsic and 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 is the source of felsic magma?
A large heat source is required for forming large volumes of felsic crustal melts and is usually supplied by the mantle via basalt. Hydrous arc basalt formed by cold slab subduction is voluminous, and its heat transfer with high water content may have melted crustal rocks leading to effective felsic magma production.
What is the meaning of felsic?
In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. … Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium.
Is felsic magma explosive?
Felsic lavas are not as hot, high in silica and volatiles, and have a high viscosity. They are thick and gooey and resist flowing. Their high volatile content makes them potentially highly explosive.
What is the difference between mafic and felsic igneous rocks?
Chemically, mafic rocks are enriched in iron, magnesium and calcium and typically dark in color. In contrast, the felsic rocks are typically light in color and enriched in aluminium and silicon along with potassium and sodium. The mafic rocks also typically have a higher density than felsic rocks.
Is felsic intrusive or extrusive?
For example, a coarse-grained, felsic igneous rock is not only a granite, it is an intrusive igneous rock that formed from slow cooling and crystallization of a body of magma within the earth’s crust. The intrusion of large bodies of granite—batholiths—is usually part of the origin of a mountain range.Do felsic magmas erupt underwater?
The resulting underwater eruptions produce long linear, basaltic mountain ranges and large areas covered with lava called flood basalts. Flood basalts also occur on continents.
…
| MAGMA COMPARISON | ||
|---|---|---|
| Property | Mafic Magma | Felsic Magma |
| Eruption Type | effusive | explosive |
| Location | hot spots, mid-oceanic ridges | subduction zones |
Is lava Hot or cold?
When lava first breaks through Earth’s surface, it is an extremely hot liquid. On average, fresh lava can be between 1,300° F and 2,200° F (700° and 1,200° C)! Depending on its exact temperature, fresh lava usually glows either orange/red (cooler) or white (hotter).What is the viscosity of felsic?
CONTROLS ON EXPLOSIVITY
| SiO2 | MAGMA TYPE | VISCOSITY |
|---|---|---|
| ~50% | mafic | low |
| ~60% | intermediate | intermediate |
| ~70% | felsic | high |
What melts first mafic or felsic?
The most mafic minerals in a melt (i.e. those with the highest melting point) will be the first to crstallize out, leaving an increasingly felsic magma. The sequence in which minerals crystallize out of magma was worked out by N. L. Bowen in the early 20th century: Bowen reaction series.
What is the viscosity of basaltic magma?
10,000 to 100
Viscosity of MagmasThus, basaltic magmas tend to be fairly fluid (low viscosity), but their viscosity is still 10,000 to 100,0000 times more viscous than water.
What is viscosity in magma?
Viscosity of MagmasViscosity is the resistance to flow (opposite of fluidity). 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).
How is mafic magma produced?
In general, melting of a mantle source (garnet peridotite) results in mafic/basaltic magmas. Melting of crustal sources yields more siliceous magmas. In general more siliceous magmas form by low degrees of partial melting. … So, melting a mafic source thus yields a felsic or intermediate magma.How is mafic formed?
INTRODUCTION. Mafic rocks that constitute the igneous oceanic crust are created at mid-ocean ridge seafloor spreading centers as a byproduct of partial melt from upwelling mantle. Through various parts of the spreading process, permeability can be generated in both the intrusive gabbros and extrusive basalts.
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 is basaltic magma?
Basaltic lava, or mafic lava, is molten rock enriched in iron and magnesium and depleted in silica. Basaltic magmas are formed by exceeding the melting point of the mantle either by adding heat, changing its composition, or decreasing its pressure. … Underwater, basaltic lavas are erupted as pillow basalts.Why is a felsic magma much more likely to produce an explosive eruption?
Why is felsic magma much more likely to produce an explosive eruption? … Felsic magma has a high viscosity, which will tend to stick in and clog volcanic conduits.
Whats the definition of foliated?
Definition of foliated
1 : composed of or separable into layers a foliated rock. 2 : ornamented with foils or a leaf design.
What is the other term for felsic?
In order for a rock to be classified as felsic, it generally needs to contain more than 75% felsic minerals; namely quartz, orthoclase and plagioclase. Rocks with greater than 90% felsic minerals can also be called “leucocratic”, meaning ‘light-coloured’.
What is the only metamorphic rock produced by contact with magma lava?
The area affected by the contact of magma is usually small, from 1 to 10 kilometers. Contact metamorphism produces non-foliated (rocks without any cleavage) rocks such as marble, quartzite, and hornfels. In the diagram above magma has pushed its way into layers of limestone, quartz sandstone and shale.
What type of volcano has felsic lava?
Composite volcanoes
Composite volcanoes are made of felsic to intermediate rock. The viscosity of the lava means that eruptions at these volcanoes are often explosive (figure 2).
How does viscosity affect volcanic eruptions?
Viscosity is the ability of a liquid to resist flowing. This means liquids with a higher viscosity are thicker and do not flow as easily. … Magmas with a higher SiO2 content have a higher viscosity. Ultimately, the viscosity of a magma will determine the shape a volcano takes over continued eruptions.
Which of the following best explains why felsic magma is more viscous than mafic magma?
High-viscosity lava does not flow quickly. … Which of the following best explains why felsic magma is more viscous than mafic magma? Felsic magma contains more silica. Which volcanically active location is most likely to have a fissure eruption?
How does Magma differ from lava?
Scientists use the term magma for molten rock that is underground and lava for molten rock that breaks through the Earth’s surface.
