What happens when each of these erupt? In what tectonic setting would you find volcanoes ejecting these types of magma?
I have a hard time understanding this...
2007-02-25 16:48:22 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Earth Sciences & Geology
Basaltic magma is made up of mostly mafic minerals. Rhyolitic magma has high levels of felsic minerals. Andesitic magma is composed of intermediate minerals -- not quite mafic, not quite felsic, or a fairly even mixture of mafic and felsic minerals.
Mafic minerals include olivine, pyroxene, amphibole, biotite and other micas, augite and the calcium-rich plagioclase feldspars (wikipedia "mafic"). Mafic magma (basaltic magma) will have a fairly low viscosity and is associated with shield volcanoes (Mauna Kea for example), and mid ocean spreading centers.
Felsic minerals include quartz, muscovite, orthoclase, and the sodium rich plagioclase feldspars (wikipedia "felsic"). Felsic magma (rhyolitic magma) is much more viscous and is associated with explosive volcanic eruptions found in Composite volcanoes (also called Stratovolcanoes). An example of a Stratovolcano would be Mount St. Helens. These volcanoes are usually found along subduction zones.
Andesitic magmas are typically composed of plagioclase plus pyroxene and/or hornblende. Biotite and quartz and iron-titanium oxides are common accessory minerals. Alkali feldspar may be present in minor amount (wikipedia "andesite"). Typically this type of magma will also form Stratavolcanoes - they are formed when oceanic crust (which is mafic) subducts under continental crust (which is felsic) - giving you a mix of mafic and felsic minerals.
2007-02-25 19:46:14 · answer #1 · answered by brooks b 4 · 1⤊ 0⤋
Magma Properties
2016-12-12 10:00:45 · answer #2 · answered by georgene 4 · 0⤊ 0⤋