Types of Magma

We are almost in the middle part discussing all about volcanoes. Let us proceed and know what do volcanoes have for them to erupt. This post tells us about the different kinds of magma, a hot fluid or semifluid material below or within the earth's crust. There are three different kinds so what are we waiting now. Let us start tackling these three types.

THREE TYPES OF MAGMA

1. Basaltic Magma

Basaltic magma is another term for mafic magma. Mafic lava is molten rock that is enriched in iron and magnesium and low in silica. When mafic magma cools on the earth's surface, it forms basalt, which is why mafic magma is commonly called 'basaltic magma.' [1]

Example of volcano with basaltic magma is Mount Kilauea.

2. Andesitic Magma

Andesitic magma a dark-colored volcanic rock composed essentially of plagioclase feldspar and one or more mafic minerals, as hornblende or biotite. [2]

3. Rhyolitic Magma

A type of magma formed by differentiation from basaltic magma in combination with assimilation of siliceous material, orby melting of portions of the earth's sialic layer. [3]

Example of volcano with basaltic magma is Mount Saint Helens.

Types of magma are determined by chemical composition of the magma. Three general types are recognized:

Basaltic magma -- high in Iron, Magnesium, low in Potassium, Sodium
Andesitic magma -- intermediate. in Iron, Magnesium, Potassium, Sodium
Rhyolitic magma -- low in Iron, Magnesium, high in Potassium, Sodium [4]

The eruption temperature of various magmas is as follows: Basaltic magma - 1000 to 1200 o Andesitic magma - 800 to 1000 o Rhyolitic magma - 650 to 800. [4]

Basaltic magma has Basalt with 45-55 SiO2 %

Andesitic magma has Andesite with 55-65 SiO2 %,

Rhyolitic magma has Rhyolite with 65-75 SiO2 %,

Higher SiO2 (silica) content magmas have higher viscosity than lower SiO2 content magmas (viscosity increases with increasing SiO2 concentration in the magma).
Lower temperature magmas have higher viscosity than higher temperature magmas (viscosity decreases with increasing temperature of the magma).

Summary Table of Comparison

(http://www.tulane.edu/~sanelson/Natural_Disasters/volcan&magma.htm)

References:

[1] http://study.com/academy/lesson/basaltic-lava-definition-characteristics.html [2] http://www.dictionary.com/browse/andesitic [3] https://encyclopedia2.thefreedictionary.com/rhyolitic+magma [4] http://www.tulane.edu/~sanelson/Natural_Disasters/volcan&magma.htm