The thermite reaction, otherwise known as the Goldschmidt reaction, is a spectacular, highly exothermic reaction. The thermite reaction can be described by the chemical equation below:
Fe2O3(s)+2Al(s)→Al2O3(s)+2Fe(s)
This reaction is initiated by heat (burning Mg) and becomes self-sustaining. The reaction generates oxygen and therefore combustion occurs even in the absence of oxygen. The reaction creates so much heat that the iron generated is melted. This reaction is mostly used in welding of big girders.