The cause of the Cretaceous/Tretiary transition remains one of the most controversial scientific topics of this decade, with the debate continuing between advocates of an impact or a volcanic cause. The occurrence of a catastrophic event of an enormous scale is, however, unquestioned. Rather, the debate concentrates on whether the event was part of an episodic process and whether it might be of extraterrestrial or endogenous origin. The case for an internal cause of the transition has been strengthened recently by the dating of the Deccan basalts to very near 65 Ma and by the devolopment of a model of a volcanic mechanism the produces shocked quartz. The evolving controversy is reviewed here to enliven debate in a college-level seminar.