With the aid of diagrams, describe tectonic models for the stretching and rifting of continental crust and explain the circumstances in which magmas are produced. How does this magmatism enable testing of the tectonic models?

With the aid of diagrams, describe tectonic models for the stretching and rifting of continental crust and explain the circumstances in which magmas are produced. How does this magmatism enable testing of the tectonic models?