Extraterrestrial Mass Extinctions

You probably thought that all of the possible books concerning the dinosaur extinction event had been written and the subject was now old news. Not so fast, friends. The End of the Dinosaurs, Chicxulub Crater and Mass Extinctions by Charles Frankel has just recently been published. This 1999 Cambridge University Press book of 223 pages retails for $24.95. End of the Dinosaurs was originally published in 1994 in French as La Mort des Dinosaurs. This version is the first English edition and has been updated from the original.

If you are like me you may not have heard of Charles Frankel before this. Frankel was born in France but attended universities in the U.S.A. His specialties are in plate tectonics and planetary geology. He has previously published Volcanoes of the Solar System through Cambridge University Press in 1996.

I can hear you now, "What more can be added? OK, an asteroid hits the earth 65 million years ago, bad things happen, the dinosaurs and some other creatures die, and mammals take over, end of story. We've heard it all before." You may think that you've heard it all but I assure you that End of the Dinosaurs has additional information and adds material that had not been approached in most of the previous books about this mass extinction.

In the first chapter of this eight-chapter book, Frankel moves through sections on the meaning of extinction, descriptions of the top five mass extinctions, and a thorough representation of the world at the end of the Cretaceous. He further shows that the causes for the extinction of the dinosaurs are not evident in their fossil remains. This problem prompted paleontologists to study the changes in other creatures during the Cretaceous to Tertiary transition (K-T). To this end, fossils of plankton were sought at the K-T boundary. The search for sites exposing the K-T transition led to the now famous site in Italy called Gubbio. The chapter ends with a presentation of the competing theories of the causes for extinction.

Chapter two begins with the story of the serendipitous discovery of the now famous Iridium anomaly at Gubbio. One of the answers scientists needed to know was the time that the clay layer took to form at the K-T boundary. The team headed by Luis and Walter Alvarez knew that the amount of cosmic Iridium that settles to earth continuously does so at a constant rate. They felt that knowing the rate and the amount of Iridium in the K-T clay would determine the time of formation. They had not counted on what they found - Iridium concentrations at 30 times the normal. Out of their research came the extraterrestrial impact hypothesis. The rest of the chapter describes further evidence that supported the impact theory. Frankel next presents the controversies surrounding the impact hypothesis. Many of the differences were rooted in the long accepted belief in uniformitarianism - all geological processes of the past happened at gradual uniform rates just as they operate today. There was therefore a strong core of scientists who believed in explanations for the dinosaur extinction based upon natural gradual earthly processes. Amongst these were the vociferous and unwavering team of Charles Officer and Charles Drake. These two scientists adhere even today to their theory of natural but extreme volcanism as the extinction cause despite insurmountable evidence to the contrary. Others supported any number of alternative theories that were all based upon a gradual extinction of the dinosaurs prior to the sudden crash at the K-T boundary.

Two chapters are devoted to the search for and discovery of the Chicxalub crater. There is a lot of information here about impact craters in general. At the beginning of the search for an impact crater, Chicxalub was not even known to be an impact crater. The other candidate craters close to the right age were all re-examined and found to be generally lacking in size. After newer dating methods were also applied, none of these was of the correct age. Scientists had to discover a new impact site. Evidence of an extremely large tsunami of the right age was found along the Gulf coast of North America and on Carribean islands. The search narrowed and Chicxalub was eventually found in the Yucatan.

I found chapter six to be a chilling description on the immediate effects of the impact. Although other books that I have read also gave descriptions of these events, I found this one to be much more frightening. Frankel covers each of the impact's effects and explains what the particular effect had on the earth and its environments. You may have thought that our weather over the past few years has been extreme. Well, consider hurricanes, tidal waves, global wild fires consuming almost all plant life, poisonous gasses and toxic water supplies, and global cooling followed by global warming - many of these happening concurrently. These disturbing descriptions are accompanied by the evidence that supports these theories. It may amaze you as it did me of the global nature of this event. Living on the other side of the globe from the impact did not improve survival rates. Frankel's descriptions really bring this home. What could survive? Not much: seeds, land animals staying in burrows, marine animals in deeper waters [This presents a possible sales feature for underground houses].

The next topic explored in End of the Dinosaurs is that of the possible interrelationship of other extinction events and extraterrestrial impacts. Here we get to look at the extinctions ending the Ordovician, the Devonian, the Permian, the Triassic, and the Jurassic. Other extinctions are examined as well but in this chapter we find that links to impacts at these extinction events is tenuous at best.

Frankel closes with an interesting chapter wherein he explores just what is the impact hazard today and in the near future. Once again much material is presented about recent earthly impacts and recent impacts within our solar system. The probability of impacts from asteroids or comets is thoroughly discussed as are sky watch programs for early warnings. In closing, Frankel presents practical means that could be used to protect the earth from destructive visitors from space.

Frankel gives the reader a truly worldwide view of the scientific work done by researchers from many countries. Most of the other books that I have read on the K-T extinction have glossed over the work of these other scientists. In total I felt that End of the Dinosaurs gave a more complete picture of the entire process that was involved. By adding chapters on other extinctions and possible links to impacts and the probabilities of impacts in the future, Frankel has rounded out the book by stimulating the reader with the relevance of paleontology to the present. The writing style of Frankel makes End of the Dinosaurs a quick enjoyable read.

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