Magma is a high-temperature, silicate-dominated molten or partially molten substance generated within Earth’s crust and mantle by decompression melting, flux melting, or heat transfer. It consists of a continuous liquid phase containing dissolved volatiles (e.g., H₂O, CO₂, SO₂), suspended crystals, and sometimes entrained xenoliths. Its physicochemical properties—temperature, viscosity, density, and volatile content—are governed by bulk composition (mafic to felsic), pressure, and crystallinity. Magma behaves as a complex multiphase fluid, undergoing differentiation by fractional crystallization, assimilation, and mixing, and on ascent can evolve into eruptible magma that degasses and solidifies to form igneous rocks.
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