Prologue

Riddles of the Terrible Lizards. American Scientist 52 227-246. (p. 231) 2. Leakey, M. (1996). Personal communication. 3. Dodson, P. (1990). Counting Dinosaurs How Many Kinds Were There Proceedings of the National Academy of Sciences of the United States of America 87 7608-7612. 4. Gartner, S., and J. P. McGuirk (1979). Terminal Cretaceous Extinction Scenario for a Catastrophe. Science 206 1272-1276. (p. 1276) 5. Eliot, T. S. (1952). The Complete Poems and Plays. New York...

CHAPTER

Good Advice. New York Quadrangle Books, (p. 44) Officer, C. B., and C. L. Drake (1983). The Cretaceous-Tertiary Transition. Science 219 1383-1390. Officer, C B., and C L. Drake (1985). Terminal Cretaceous Environmental Events. Science 227 1161-116'. Glen, W. (1982). The Road to Jaramillo. Stanford, Calif Stanford University Press. Berggren, W. A., D. V. Kent, et al. (1995). A Revised Cenozoic Geochronology and Chrono stratigraphy. Geochronology, Time Scales, and...

Cryptoexplosion Structures And Impact Markers

The Steinheim Basin in Germany was one of the first cryptovolcanic structures to be described. Although it was initially put down to meteorite impact, this idea quickly gave way. to the more orthodox view that the basin and others like it had been formed by ascending volcanic gases that fractured the rocks but whose associated lavas remained hidden, giving rise to the name cryptovolcanic for the structures cryptoexplosion later became the preferred term). Curiously, however, the deeper the...

Triumph Of The Volunteers

Management expert Peter Drucker has pointed out that one out of every two adults is a volunteer when they are included, the nonprofit sector is the nation's largest employer. Without their corps of stalwart, dedicated, (and unpaid), volunteers, the museums of America (and most of the rest of the nonprofit sector) would be but pale shadows of themselves. Sheehan and his colleagues at the Milwaukee Public Museum realized that the dinosaur specimens in museum and...

Resistance

After Luis Alvarez informed a physicist colleague that the absence of Pu 244 in the boundary clay negated the supernova theory, he received the reply Dear Luie You are right and we were wrong. Congratulations. To Luis, this response exemplified science at its best, a physicist reacting instantly to evidence that destroys a theory in which he previously believed.2 He could never understand why the paleontologists did not react the same way. He could have taken a lesson from the theory of...

Iol

Late Tom Schopf, told Sepkoski that he was up for tenure consideration that year. Such an announcement, like the discovery that one is to be hanged in a fortnight, concentrates the mind wonderfully.3 In a panic to publish quickly, the young professor decided that his best bet was to try to get out an article based on his compendium. Sepkoski worked frantically for months, only to have Schopf return to say that he had been mistaken Sepkoski's tenure would be decided the following year. But by...

Preface

What killed the dinosaurs For 150 years, that question has stumped even the best scientists. But no longer. At last the great mystery has been solved. The story of the solution is fascinating in its own right, and the answer helps us to understand our place in the universe It raises the revolutionary possibility that the history of the earth, and of life upon it, has been altered repeatedly by a nearly invisible, and previously unrecognized, cosmic process. It forces us to ponder the role of...

Clues

Fortunately, the crater detectives had the benefit of some important clues. At first, the clues seemed to point toward an oceanic location for the crater, a worrisome possibility given the likelihood that in that case it would no longer be visible. As the K-T boundary clay continued to be studied, however, other evidence began to come to light that suggested a continental landing site. For example, the boundary clay contains a small but persistent fraction of broken rock fragments, the majority...

The Grea

The dinosaurs were among the most successful creatures ever to live. They reigned for 160 million years, far longer than the few million that our genus, Homo, has so far existed. Dinosaurs came in all sizes and shapes small and large, fast and slow. Except for today's blue whale, no creature has been larger, and surely none have been as frightening. Some, like Apatosaurus, the 80-foot, 30-ton thunder lizard whose tread shook the ground like an earthquake, were herbivores. Others, like the...

Preemptive Strike

If the Alvarez theory is correct, the change from Cretaceous time to Tertiary time happened instantaneously, everywhere around the globe, in which case the K-T boundary clay can represent but a mere eyeblink of geologic time a few hundred or a few thousand years at most. Furthermore, the boundary would have to be the same age everywhere. Officer and Drake claimed to have evidence that, on the contrary, the age of the boundary differs by hundreds of thousands of years at different locales. If...

Info

Lower curves show how far in each direction the actual curve might lie. If we knew which craters had associated extinction events, their positions could be plotted on the impact-kill curve. As noted in the discussion of Table 4, however, the only crater about which we are certain is Chicxulub. Michael Rampino and Bruce Haggerty21 make an educated guess that three other craters can be added to the list as shown in Table 6 and Figure 24. Is the impact-kill curve credible on its face It predicts...

Topography

Kevin Pope, a consulting geologist now associated with the Jet Propulsion Laboratory, and two colleagues, came close to being the first to rediscover Chicxulub. He and Charles Duller of NASA were examining Landsat high-altitude satellite photographs, trying to determine the relationship between the ancient Mayan sites on the Yucatan Peninsula and the location of surface water deposits. They soon noticed a set of small ponds, which they later found went by the Mayan name of cenotes, that were...

T Esting C Hicxulub

The geophysical maps of the Chicxulub feature Figure '4 showed it to have the form of a buried crater. The announcement of its discovery by a card-carrying pro-impactor, Alan Hildebrand, galvanized his colleagues into furious activity. Today, only a few years later, a vast amount of information has been assembled about the Chicxu-lub structure, more than enough to test the proposal that it is the K-T impact crater. Following the list of predictions given earlier, I will summarize the results of...

The Son In Italy

Scaglia Rossa

Given his family history, it is not surprising that young Walter became a scientist himself. No one could have followed in his father's footsteps, and wisely in retrospect, Walter chose not to try but to follow his own love, geology. He earned his doctorate at Princeton under Professor Harry Hess and, until Qaddafi expelled the Americans, worked as a petroleum geologist in Libya. In 1971 he joined the faculty at the Lamont-Doherty Geological Observatory at Columbia University, where much of the...

The Father

In a picture taken at the MIT Radiation Laboratory during World War II, his hat at a jaunty angle and a cigarette dangling from his lips, a cocky smile on his face and a coil of wire strung around his neck, Luis Alvarez appears not as the stereotypical dull, introverted scientist but more like a cross between Indiana Jones and Humphrey Bogart Figure 1 . He was a man who lived life to the fullest and continued seeking new challenges long after most would have begun to rest on their laurels....

TABLE

Candidate Craters for the Impact-Kill Curve Crater Size km species killed destroyed Hiroshima according to Figure 24, it would result in the death of about 20 percent of species. A loss of 20 percent of species every 7 million years is equivalent to a 100 percent turnover in 35 million years, which is only about 6 percent of the time that has elapsed since the Cambrian began. Thus it is more than enough to account for the record of extinction observed in the rocks. To answer Raup's question as...

Chapter A

The Logic of Scientific Discovery. New York Harper and Row. p. 41 2. Tennyson, Lord A. 1955 . In Memoriam. London Macmillan. p. 1 3. Popper, K. R. 1968 . The Logic of Scientific Discovery. New York Harper and Row. 4. Silver, L. T, and P. H. Schultz, Eds. 1982 . Geological Implications of Impacts of Large Asteroids and Comets on the Earth. Boulder, Colo. Geological Society of America. Sharpton, V. L., and P. D. Ward, Eds. 1990 . Global Catastrophes in Earth History....

Iridium H Ills

Even though later evidence appeared to offer more support for the Alvarez theory than the iridium findings, it was the Gubbio iridium anomaly that sent the Alvarezes down the trail of impact in the first place. If that particular evidence were weakened or falsified the entire theory would be in jeopardy. Iridium had already met two tests It proved uncommon in the geologic record and, as shown by the presence of the iridium spike in freshwater rocks from the Raton Basin, did not come from...

Cosmic Winter

When presenting a theory far outside the mainstream, the first question is whether it is credible. The burden of establishing credibility properly rests with the proposers if they are unable to do so convincingly, the theory is best let lie. A theory whose credibility has been weighed and found wanting may not have been proven false, but the finding does serve to direct research elsewhere. On the other hand, as we shall see, too often in geology a magisterial authority has made a pronouncement...

Ammonites

Ammonites were mollusks, like the squids and octopuses, that ranged from about a centimeter to a meter in size. Their intricately coiled and chambered shells provide some of our most beautiful fossils. The ammonites first appeared in the mid-Paleozoic, survived even the deadly end-Permian extinction, when 96 percent of all species died, and expired at the end of the Cretaceous, 330 million years after their arrival. Geologists, including Darwin whose contributions to that field earn him the...

The Zircon Fingerprint

Although the list of features of Chicxulub is long and closely matches those to be expected of the K-T impact crater, each individual piece of evidence is circumstantial. To be precise, what has been demonstrated is that on the Yucatan Peninsula, buried under a half-mile of sedimentary rock, lies a crater of K-T age that is somehow linked to the unique Haitian tektites. What has not been demonstrated is that this crater is the parent of the K-T boundary clay around the world. It is highly...

Theory On Trial

It must be possible for an empirical scientific system to be refuted by experience. Karl Popper By the early 1980s, the importance of impact in the solar system was established as a fact, as was the presence of high iridium concentrations in at least a few K-T boundary clay sites. That the Cretaceous had ended with a great mass extinction was also a fact, though the suddenness of that extinction was disputed. The Alvarezes invented a theory that tied these facts together. To explain the...

Meteor Crater

As one drives across the desert of northern Arizona, suddenly, and for no apparent reason, there looms ahead a mile-wide, nearly circular hole in the ground called Meteor Crater Figure 4 . In 1891, G. K. Gilbert, chief geologist of the U.S. Geological Survey and one of the most prestigious geologists in the world, attended a lecture in which this feature, known then for its raised rim as Coon Mountain, was described. Scattered around it were curious metallic fragments that were unlike any...

Plants

The accumulation of knowledge has meant that scientists today must practice in finer and finer subspecializations One is not a paleontologist, one is an invertebrate paleontologist specializing in ammonites or one is a palynologist, an expert not just in fossil plants, but in fossil pollen spores. One of the most beneficial by-products of the Alvarez theory is the way in which it has brought together scientists from an unprecedented variety of disciplines. Pollen specialists, for example, have...

Survival Across The Kt Boundary At Hell Creek

The Museum of Paleontology at Berkeley contains more than 150,000 curated specimens of nonmarine vertebrate fossils mammals, dinosaurs, turtles, snakes, and so on from the Hell Creek and Tullock formations. David Archibald and Laurie Bryant both former students of Clemens took upon themselves the task of sorting through this enormous database to count the number of species that were present both in the Hell Creek formation and in the overlying Tertiary rocks of the Tullock.49 They found that of...

O Ther C Ycles

Rampino and Stothers have gone on to argue for a 32 3 million-year periodicity not only in mass extinctions and impact cratering, but in a variety of other major geologic processes flood basalt eruptions, magnetic reversals, appearance of oxygen-poor oceans, large changes in sea level, and episodes of seafloor spreading. Later, Ram-pino and Bruce Haggerty went on to develop what they call their Shiva Siva hypothesis.22 If they are correct, a single cause is likely to drive most or all of the...

Ell On E Arth

To try to understand whether and how the Alvarez theory might help to explain the selectivity of the K-T extinction, we need to know what would happen when a 10-km to 15-km meteorite strikes the earth. The two halves of the Alvarez theory that impact occurred and that it caused the mass extinction are linked by the assumption that the resulting effects would be sufficiently lethal to cause the death of 70 percent of all species. The Alvarez team had precious little evidence for this assumption...

S Hocked M Inerals

Bruce Bohor's '98' discovery of shocked quartz previously found only at known impact craters and at the sites of nuclear explosions, in the K-T boundary clay in the Hell Creek area of Montana, home of T. rex convinced many geologists that impact was a reality. Glenn Izett of the U.S. Geological Survey, who wrote the definitive paper on the K-T section in the Raton Basin, spoke for them I started off as a nonbeliever. What got me was the appearance of these shocked minerals at the K-T. In the...

The Moon To The Outback

What are the objects that strike the earth from space to form craters, and how is it that they can have such devastating effect, not only to dent the solid earth, but, as claimed by the Alvarezes, to play the starring role in dinosaur extinction Astronomers have discovered that two types of cosmic objects are in orbits that sometimes intersect that of the earth comets and asteroids. Comets are dirty snowballs mixtures of mineral dust and ices that evaporate under the heat of the sun to produce...

Cratering In The Solar System

The first person to observe lunar craters was Galileo. In 1609 he trained his telescope on the moon and saw the seas the maria , the highlands, and some circular spots. He observed that as the termina-tor the sharp line separating the light and dark sides of the moon moved across, the far edges of the circles lit up before the centers. This told him that the rims of the circles were higher than their centers, which meant that they were depressions, or craters. From the length of their shadows,...

Dinosaur Fossil Evidence

We wish to learn how the dinosaurs died, not how they lived therefore our interest is in their last few million years during the late Cretaceous. How many dinosaur species were living then, where are their remains, and what do they tell us According to paleontologist Peter Dodson, only about 2,100 articulated bones of dinosaurs have been collected, and they span 160 million years.40 If spread evenly, we would have one specimen for each 75,000 years, but in fact the discovered remains of...

Are Extinction And Cratering Periodic

David Raup During the 1970s, when the Alvarezes were developing their theory, a young paleontologist named John Sepkoski was at work at the University of Rochester, compiling the ranges of geologic ages during which each family of fossil organisms lived. Recall that biologists subdivide organisms into kingdom, phylum, class, order, family, genus, and species. We belong, in the same order, to the animals, chordates, mammals, primates, hominids, genus Homo, and...

The Deccan Traps

The sharp iridium peaks, the spinel spikes described in the last chapter, and the thin boundary clay tell us that whatever the origin of the K-T event, it did not last for millions of years, or even for 1 million years. As we have seen, some think it lasted for no more than 100 years If Deccan volcanism caused the K-T event, the eruption of the traps must have started just prior to K-T time and lasted just beyond it, covering at most a few hundred thousand years. If the Deccan traps do not date...

Sampling Effects

Gradual Extinction

At the first Snowbird conference in 1981, paleontologists Phil Signor and Jere Lipps presented what has proven to be one of the most important papers in modern paleontology.11 Like some others that have had such a result, their paper was short and simple. The authors showed that sampling can have two separate but related effects on paleontological evidence, both of which make it harder to draw firm conclusions. The first is illustrated by Figure 18, adapted from their paper, which shows how the...

Losing By A Nose

Even today, in the era of electronic mail, faxes, and international flight, it is still possible for two individuals or groups to work independently, unknown to each other, and to come to the same conclusion simultaneously. This nearly happened in the case of the meteorite impact theory.13 In 1974, geologist Jan Smit began to study the K-T boundary at Caravaca, Spain, for his doctoral dissertation, focusing on the disappearance of the microscopic foramin-ifera there. At the start, he thought...

Olcanic Iridium

The picture of iridium anomalies as uniquely diagnostic of meteorite impact began to cloud in the mid-1980s, lending additional credence to the volcanism theory. The chemistry of aerosols suspensions of fine solid or liquid particles in gases emitted from Kilauea Volcano in Hawaii had been under investigation by scientists from the University of Maryland.5 Although for five years they detected no iridium, aerosols from the 1983 eruption unexpectedly contained up to 10,000 times as much iridium...

An Exercise In Newspeak

Though modern geologists rejected a strict interpretation of Lyell's uniformity of state, by the 1950s most of those in North America had come to believe that at least the outer appearance of the earth, with its continents and ocean basins, had not changed dramatically cer-tainly continents had not drifted. The notion that seafloors spread out to plunge beneath continents, that the ocean basins are geologically young, that the continents have never been in the same place twice all proved hard...

Chapter Io

The Debate over Dinosaur Extinction Takes an Unusually Rancorous Turn. New York Times, C1-C4. p. C3 2. Benton, M. J. 1990 . Scientific Methodologies in Collision The History of the Study of the Extinction of the Dinosaurs. Evolutionary Biology 24 371-400. 3. Schopf, T. J. M. 1982 . Extinction of the Dinosaurs A 1982 Understanding. Geological Implications of Impacts of Large Asteroids and Comets on the Earth, eds. L. T. Silver and P. H. Schultz. Boulder, Colo....

Indian Iridium

By the mid-'980s, even the fiercest opponent of the Alvarez theory had to admit that the iridium anomalies, however much they spread above and below the K-T boundary and whatever their cause, did mark the position of the K-T boundary and must reflect a global event. If Deccan volcanism was the source of that iridium, it might then be possible to find an iridium-rich K-T boundary layer amidst the Deccan basalt flows. An intensive search for iridium by the French team came up empty, however....

Iridium

The magnetic reversal time scale offered one possibility for determining how much time the clay layer represented The particular pattern of reversals above and below the clay might bracket its age of formation and allow an upper limit to be placed on how long it could have taken to deposit the layer. Alas, during this period of geologic history the reversals had not happened often enough All that could be told is that the clay layer fell within a 6-m section of limestone deposited during a...

I

Jurassic Sea Level

Event to account for the demise of the dinosaurs.3 Writing in 1982, Archibald and Clemens used different words to make the same point At present, the admittedly limited, but growing, store of data indicates that the biotic changes that occurred before, at, and following the Cretaceous-Tertiary transition were cumulative and not the result of a single catastrophic event.4 In October 1982, only two years after the original paper appeared in Science and before most paleontologists had even begun...

The Tempo Of Evolution

There may be an additional way to shed light on the role of impact by focusing not on the mass extinctions themselves, but on the normal intervals of background extinction in between. If impact drives mass extinctions, then in the times between impact events, few extinctions would be expected. Can we tell whether the tempo of extinction and evolution in between the large extinctions is consistent with a history of impact After Darwin, evolutionists came to have the view that natural selection...

Foraminifera

Calcareous Foraminifera

Planktonic foraminifera Figure 2' , nicknamed forams, are one-celled, amoebae-like protozoa that float at various depths in the oceans, eating the still smaller photosynthetic algae and secreting calcareous shells that survive the foram's demise. They evolve rapidly figure 2 i Foraminifera. Photo courtesy of Brian Huber and National Museum of Natural History. figure 2 i Foraminifera. Photo courtesy of Brian Huber and National Museum of Natural History. and spread out over wide areas, making...

Bioturbation And Reworking

As discussed in an earlier chapter, many marine animals clams, for example burrow downward into the sediment beneath, dragging down younger material from the surface and bringing older material back up, an effect known as bioturbation. When these disturbed sediments eventually harden into rock, the fossils that they contain, as well as any iridium and tektite layers, are stretched out over a broader range than the one in which they were deposited. Studies of bioturbation in modern sediments...

Clues From The Fossil Record

With respect to the apparently sudden extermination of whole families or orders ... we must remember what has already been said on the probable wide intervals of time between our consecutive formations and in these intervals there may have been much slow extermination. Charles Darwin Craters are physical features. Even one hidden under a kilometer of rock can be discovered using geophysical techniques, then drilled, and samples brought back to the surface and studied in the laboratory. As more...

Without Help From A Comet

Walter Alvarez could have told his father that it is hard to find any idea in the history of science more consistently and continuously spurned by authorities than the notion that meteorite impact has in any way affected the earth. The rejection stretches back to the dim beginnings not only of geology but of science itself. In the 1680s, William Whiston, mightily impressed by the great comet that had opened that decade, wrote that God had directed the comet at the earth and that its impact had...

Alvarez Predictions

The Alvarez theory revolves around two key hypotheses 65 million years ago, a meteorite struck the earth, and 2 the aftereffects of the impact caused the K-T mass extinction. Since one can accept the first without accepting the second, they need to be kept separate although the Alvarezes did not . In the rest of this chapter, I will examine the evidence for the first half of the theory. The second half is covered in Chapters 8, 9, and 0. Although Luis Alvarez himself identified 5 pre- and...

Mysterious Spherules

While working on the iridium-rich K-T boundary clay at Caravaca, Spain, in 1981, Jan Smit and G. Klaver discovered rounded, sand-sized grains of feldspar.42 Similar spherules showed up at the other prominent K-T sites and in several deep-sea cores that captured the boundary. On the basis of the mineralogy and texture of the spherules, Smit, Alessandro Montanari, the Alvarezes, and their colleagues concluded that they were congealed droplets of molten material that had been blasted aloft in the...