Explain the difference between matter made up of more than one element in matter made up of only one element

A substance that cannot be broken down into chemically simpler components is an element.

A substance that can be broken down into chemically simpler components (because it has more than 1 element) is a compound. Example: Water id a compound composed of elements hydrogen and oxygen.

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

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