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MAGMA

Elements: Si, Al, Fe, Ca, Mg, Na, K, H, O
Compositional variation: SiO2 (45% - 75% by weight),
Al2O3, CaO, MgO, FeO, and H2O
Dissolved gases (0.2% to 3%): water vapor and CO2
Melting temp.: 800°C to 1400°C Viscosity of the magma
depends on its silica content
Viscosity of the magma depends on its silica content
High Si = more viscous = slower

TYPES

Basaltic magma remains liquid and rises to the surface to erupt.
Granitic magma usually solidifies within the crust.

Typical Granitic Magma	Typical Basaltic Magma
70% silica; up to 10% water	50% silica; 1% - 2% water
viscous magma	less viscous
rises slowly	flows or rises easily
water loss cause it to solidify within the crust	remains liquid since water loss is relatively unimportant

Some terms:

Eutectic Temperature: the melting temperature of rocks that is lower than the melting temperature of its constituent minerals
Partial Melting: when certain minerals are melted during the start of melting by rocks
Fractionation: a process when magma is separated from rock that has not undergone complete melting

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