Question

The amount of silica in the magma and temperature are factors that determine the viscosity of magma. True OR False.

Answer 1

Answer:

TRUE

Explanation:

The chemical composition of a magma affects viscosity in a complex way. The elements in a magma can be divided into three-dimensional atom lattice elements and non-three-dimensional atom lattice elements. Si4 + and to a lesser extent Al + 3 and Fe3 + are the main three-dimensional network forming elements, while Mg2 + and Ca + are the main non-three-dimensional network forming elements. In silicate minerals, four oxygen ions are bonded to a silica cation forming a tetrahedral configuration. The union of silica and oxygen tetrahedra is commonly called polymerization. The more silica (SiO2) there is in the composition of a magma, the more polymerized this magma is, consequently, also the more viscous. Studies have shown that rhyolitic (72-75% SiO2) magmas are more polymerized and viscous than dacitic (65-71% SiO2) and andesitic (53-64% SiO2) magmas, and these are more polymerized and viscous thanbasaltics  magmas. (45-52% SiO 2). Ultramafic magmas, for example Komatiitics, contain less silica (<45% SiO2) than basaltic magmas and are therefore less polymerized and viscous.

Answer 2

TRUE

A magma's viscosity is largely controlled by its temperature and its amount of silica.