25 years of the impact-volcanic controversy - Is there anything new under the sun or inside the earth?

The evidence for meteorite impact and internal volcanic processes (cryptovolcanism) as the cause of the K-T extinction and for cryptoexplosion structures is briefly reviewed. It is shown that numerous studies reinforce the view that shock-metamorphic features uniquely indicate shock pressure from 5 GPa to over 50 GPa, that no generally accepted shock-metamorphic features have been found in unquestioned volcanic structures, and that no internal process has been demonstrated to produce the required shock pressures. This history therefore supports an impact origin for both cryptoexplosion structures and the K-T event. Future discoveries required to make the cryptovolcanic theory a respectable alternative are discussed.