25 years of the impact-volcanic controversy: Is there anything new under the Sun or inside the Earth?
Article first published online: 3 JUN 2011
©1990. American Geophysical Union. All Rights Reserved.
Eos, Transactions American Geophysical Union
Volume 71, Issue 17, pages 411–414, 24 April 1990
How to Cite
1990), 25 years of the impact-volcanic controversy: Is there anything new under the Sun or inside the Earth?, Eos Trans. AGU, 71(17), 411–414, doi:10.1029/90EO00154.(
- Issue published online: 3 JUN 2011
- Article first published online: 3 JUN 2011
An interesting historical perspective on the current controversy about the cause of the Cretaceous-Tertiary (K-T) extinction has been provided by more than 2 decades of debate on an earlier but equivalent question: Are the circular, highly deformed cryptoexplosion structures, and the shock-metamorphic features they contain, astroblemes formed by meteorite impact, or are they formed by internal volcanic processes (cryptovolcanism)? During the last 25 years of this debate, numerous studies have reinforced the view that shock-metamorphic features uniquely indicate shock pressures of from about 5 GPa to > 50 GPa; no generally accepted shock-metamorphic features have been found in unquestioned volcanic structures; and 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 include undisputed shock features, for example, shatter cones, shock lamellae, stishovite, lechatelierite, in a volcanic structure; high Ir contents (>1 ppb) in volcanic ejecta layers; and a rigorous and testable theory for producing high shock pressures by internal processes.