Key Earth Science Links
Dinosaur Extinction Web Sites
Dinosaur Extinctions, Enchanted Learning Software®. Provides information and colorful graphics about mass extinctions, the asteroid theory for the Cretaceous extinction, other theories for the dinosaurs extinctions, and explains how scientists study and test these theories.
DinoBuzz--What Killed the Dinosaurs? University of California, Berkeley. This site provides a description of mass extinctions, what types of animals and plants died during the Cretaceous extinction, and an interesting list that shows how scientists test extinction hypotheses. A section on Invalid Hypotheses discusses theories that most scientists no longer believe in. The Current Arguments section discusses the many different theories that are presently debated concerning the Cretaceous extinction, their common ground, and their differences.
Lecture 24--The Impact Theory of Mass Extinction. Columbia University. Part of an online lecture series for Dinosaurs and the History of Life. Presents the history of the impact theory, from its original origins to the multiple lines of testing and different types of data that have been used to support the theory.
Blast from the Past!, National Museum of Natural History, Smithsonian Institution site that offers a short description of the evidence for a meteor or comet impact at the Cretaceous/Tertiary boundary collected from cores in the Gulf of Mexico. There is also a reference list of journal articles (some on line) concerning the possible impact.
Impacts and Dinosaur Extinctions, A site of the Planetary Society®, a non-profit society founded by Carl Sagan. This site provides provides information about the theory that a comet or meteor impact caused the extinction of the dinosaurs. Transcripts and images from several field expeditions to Belize and surrounding countrys describe the evidence for a catastrophic impact.
Researchers Drill into Dinosaur Crater . BBC News, 2000. Short report on drilling into the Yucatan to find evidence for the K-T impact. Picture of the space rock and short summaries of various theories about what type of dust was ejected into the atmosphere after the impact.
Dino Crater Viewed from Space . BBC News, 2003. Space Shuttle image of the Yucatan peninsula showing the tell-tale outline of the buried crater.
Quick Demise for the Dinosaurs. BBC News, 2001. Summary of research that concludes that dinosaurs became extinct within 10,000 years of the impact. Good short explanation of extinction theories, including volcanic theory, with some images.
Unraveling the Chicxulub case. Sever, M., Geotimes. Easy-to-read summary of the search for a meteor crater following the proposal of the Alvarez asteroid theory in 1980, the discovery of Chicxulub, and the research that followed the initial discovery. A sidebar also discusses research on modelling the effects of an impact on climate.
Earth suffered pulses of misery….Science news, 2002. Short summary of research that models global wildfires that would have been formed by the impact of the meteorite in the Yucatan peninsula at the end of the Cretaceous Period.
Some key references (technical articles): impact theory
There is a vast amount of research on this mass extinctions. The following is a short list of some important and/or interesting research papers. You may be able to get these online through JSTOR, Science Direct or other online technical journal searches, or you may be able to get them through interlibrary loans)
- Alvarez, L.W., Alvarez, W., Asaro, F., and Michel, H.V., 1980, Extraterrestrial cause for the Cretaceous-Tertiary extinction: Science, v. 208, p. 1095-1108. This is the research paper that got the public (and scientists) excited about mass extinctions and the theory that a meteor impact caused the extinction of the dinosaurs. The evidence for a meteor impact was based on concentrations of a rare element called iridium at the Cretaceous-Tertiary (Paleogene) boundary. Note that at the time of this publication the impact location was not known.
- Bourgeois, J.T., Hansen, T.A., Wiberg, P.L., and Kauffman, E.G., 1988, A tsunami deposit at the Cretaceous-Tertiary boundary in Texas: Science, v. 241, no. 4865, p. 567-570. Discusses evidence for a tsunami (tidal wave) deposit along the Brazos River in Texas at the Cretaceous-Tertiary (Paleogene) boundary, which is hypothesized to have been 50-100 m high, and resulted from the Chixculub impact.
- Hildebrand A. R., Penfield G. T., Kring D. A., Pilkington M., Camargo Z. A., Jacobsen S. B. and Boynton W. V., 1991, Chicxulub crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatan Peninsula, Mexico: Geology, v. 19, p. 867-871. This is the study that found the smoking gun; circular gravity and magnetic anomalies indicate a buried 180 km-wide crater beneath Chicxulub, Mexico as at the Cretaceous-Tertiary (Paleogene) boundary. Concluded that it was the likely source for the Alvarez and others (1980) impact event.
- Izett, G.A., 1991, Tektites in Cretaceous-Tertiary boundary rocks in Haiti and their implications on the Alvarez impact extinction hypothesis: Journal of Geophysical Research, v. 96, p. 879-905. Identifies small, glassy, spherical fragments in the K-T boundary layer of Haiti as tektites, which are cooled fragments of ejected molten material from bolide impact sites, and hypothesizes that they resulted from the bolide impact at Chicxulub.
- Kerr, R.A., 1996, A piece of the dinosaur killer found? Science, v. 271, no. 5257, p.1806. Reports on the discovery of a tiny asteroid fragment from the K-T boundary of the Pacific Ocean that could be part of the actual Chicxulub-crater forming asteroid.
- Melosh, H. J., Schneider, N.M., Zahnle, K.J., and Latham, D., 1990, Ignition of global wildfires at the Cretaceous/Tertiary boundary: Nature, v. 342, p. 251-254. Computer modeling of global wildfires that would have been ignited by ejected material from the Chicxulub impact reentering the atmosphere and striking the ground. Note that there have been many subsequent publications that have modeled the thermal pulse and fires from the impact in different ways.
- Smit, J., and others, 1992, Tektite-bearing, deep-water clastic unit at the Cretaceous-Tertiary boundary in northeastern Mexico: Geology, v. 20, no.2, p. 99-103.Describes a tsunami deposit from northeastern Mexico at the K-T boundary that contains spherules (glass droplets) from the melt of the impact in Mexico, capped by an iridium anomaly. Note that many other papers have also found tsunami deposits at this horizon in the Gulf of Mexico area.
- Wolbach, W.L., Gilmour, I., Anders, E., Orth, C.J., and Brooks, R.R., 1988, A global fire at the Cretaceous/Tertiary boundary: Nature, v. 334, p. 665-669. Describes large amounts of soot in clay layers from the K-T boundary in different places of the world. The isotopic signature of the soot from the different sites indicates that it was from a single source, inferred to be the Chicxulub impact site.
- Pope, K., O., D' Hondt, S.L., and Marshall, C.R., 1998, Meteorite impact and the mass extinction of species at the Cretaceous/Tertiary boundary: Proceedings of the National Academy of Sciences of the United States of America, v. 95, no. 19, p. 11028-11029.
Short, non-technical summary of the importance of the Alvarez impact theory relative to geologist’s ideas about gradualistic vs. catastrophic events in earth history and the entire concept of mass extinctions.
- Schulte, P., Alegret, L., Arenillas, I., Arz, J., Barton, P., Bown, P., Bralower, T., Christeson, G., Claeys, P., Cockell, C., Collins, G., Deutsch, A., Goldin, T., Goto, K., Grajales-Nishimura, J., Grieve, R., Gulick, S., Johnson, K., Kiessling, W., Koeberl, C., Kring, D., MacLeod, K., Matsui, T., Melosh, J., Montanari, A., Morgan, J., Neal, C., Nichols, D., Norris, R., Pierazzo, E., Ravizza, G., Rebolledo-Vieyra, M., Reimold, W., Robin, E., Salge, T., Speijer, R., Sweet, A., Urrutia-Fucugauchi, J., Vajda, V., Whalen, M., and Willumsen, P. 2010, The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary: Science, v. 327 (5970), p. 1214-1218 Report outlining the evidence for an asteroid impact killing off the dinosaurs, which was reported as international consensus on the impact theory. It includes (1) summaries of data correlating the impact to the end of the Cretaceous, (2) the likely effects of the impact on the environment, (3) the consequences to life based on the fossil record, and (4) ideas for future research.
Some key references (technical articles): other theories
The following is a short list of some important and/or interesting research papers. You may be able to get these online through JSTOR, Science Direct or other online technical journal searches, or you may be able to get them through interlibrary loans)
- McLean, D.M., 1985, Deccan traps mantle degassing in the terminal Cretaceous extinction. Cretaceous Research, v. 6, no. 3, p. 235-259. Provides theory for how flood basalts in the Deccan traps would have caused increased oceanic and atmospheric CO2, which caused major perturbations in the carbon cycle, ocean acidity, and disruption of the algal productivity-gravity pump of CO2, and mass extinction.
- Wignall P.B., 2001, Large igneous provinces and mass extinctions: Earth Science Reviews, v.53, no. 1-2, p. 1-33. Examines the coincidence in timing of several large extinction events to the formation of large igneous provinces, and shows where there is good correlation (as with the Deccan traps at the end of the Cretaceous) and where there may be problems with direct correlations. In some cases, the major eruption phases appears to post-date some of the extinctions. Notes that 6 of 11 large igneous provinces (which represent periods of large volcanism) coincide with global warming and marine anoxia, suggesting that volcanic CO2 emissions have a profound effect on global climate.
Compilations of multiple research papers in single volumes
- Koeberl, C., and MacLeod, K.G., eds., 2002, Catastrophic events and mass extinctions: impacts and beyond: Geological Society of America, Special Publication no. 356, 746 p. This volume contains 56 short research papers on mass extinctions. Twenty-six of the papers concern the Cretaceous-Tertiary (Paleogene) extinction.
- Sharpton, V.L., and Ward, P.D., eds., 1990, Global catastrophes in earth history: an interdisciplinary conference on impacts, volcanism, and mass mortality: Geological Society of America, Special Publication no. 247, 631 p. This volume contains 58 short research papers on mass extinctions. Twenty-five of the papers concern the Cretaceous-Tertiary (Paleogene) extinction, and 13 papers concern meteor and comet impacts as causes of extinctions.
- Alvarez, W.M., 1997, T-rex and the crater of doom: Princeton, New Jersey, Princeton University Press, 185 p. This book begins with background information on stratigraphy, age dating, gradualistic vs. catastrophic views of earth history, and then proceeds to outline the data and history of the theory that the dinosaur extinction was caused by a meteor impact, as well as the search for and discovery of the crater responsible.