Boy, that really ties in nicely with the Dryas theory and the change in drainage patterns.
"This is what happens when you do interdisciplinary science,"
A similar thing happened with the dinosaur extinction. The asteroid idea originally came from a nuclear physicist whose son was a geologist. The only thing they had in common, besides DNA, was, of course, Cal :>)
It Came From Outer Space
By TIMOTHY FERRIS
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Walter Alvarez's scientific detective story makes the case that a giant impact killed the dinosaurs
Read the First Chapter
T. REX AND THE CRATER OF DOOM
By Walter Alvarez.
Illustrated. 185 pp. Princeton, N.J.:
Princeton University Press. $24.95.
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Walter ALVAREZ has been on the faculty at the University of California, Berkeley, for 20 years. For a couple of semesters in the early 1990's he happened to teach geology in North Gate Hall, across from the room where I was conducting a graduate research seminar. In those days, I would sometimes amble across the corridor, slip in by the back door and listen in on part of his lectures. I picked up a little geology, and with it a deepening respect for Mr. Alvarez as a teacher. An amiable, rail-thin redhead with faded blue eyes, he has a rambling, easygoing speaking style that can seem disorganized until one realizes that his anecdotes and asides arise from a considered vision of his research, and of geology in general, as a dynamic part of the larger process of human inquiry as a totality. In his lectures, he came across as a kind of working philosopher, constantly pausing to ask himself and his students just what it is scientists do, how they learn and to what extent they are justified in believing the stories they piece together and delight in telling one another.
Mr. Alvarez is highly regarded in University of California scientific circles -- no small feat on a campus that's dotted with parking marked 'NL,' reserved for its many Nobel laureates -- and even the undergraduates in his class who were not especially interested in science knew him as the man who discovered what killed the dinosaurs. But the full story was, of course, rather more tangled than that.
One of those parking spaces had belonged to Mr. Alvarez's father, the physicist Luis Alvarez, who won the prize in 1968 for his development of hydrogen bubble-chamber experiments and who recounted many of his other glittering attainments -- from X-raying the Pyramids of Egypt to analyzing the Zapruder movie of the Kennedy assassination -- in a widely read memoir, 'Alvarez: Adventures of a Physicist.' While he was alive (he died in 1988) his prominence made his son seem as inconspicuous as a small planet circling a brilliant star. The contrast was heightened by Walter Alvarez's choice of fields: geology wasn't physics, and Mr. Alvarez himself confessed, in his disarming way, that he was 'a little bit embarrassed' to be working in what was regarded at the time as a backwater science. Ironically, one of the things that made geology so dull was its habit of acting as if the cause of dinosaur extinction, rather than amounting to a monumental piece of scientific ignorance, could be dealt with by hiding it behind a cloud of pompous generalities. 'Mass extinction was treated as a nonproblem,' Mr. Alvarez writes in his deft and readable new book, 'T. Rex and the Crater of Doom.' The account in a leading textbook was typical. It declared, in self-congratulatory language, that 'whatever the cause, the latest Mesozoic was a time of trial' when many species 'were 'tried in the balance and found wanting' -- wanting in adaptiveness to the new environment.'
All that began to change when Luis and Walter Alvarez, in collaboration with a few of their Berkeley colleagues, proposed that what killed the dinosaurs, along with nine-tenths of all species then extant, was the impact of a major comet or asteroid. Their theory, widely disputed at first, enlivened and then transformed geology, and eventually helped revolutionize broader notions of how life on Earth evolved. Its triumph came with the discovery, in 1991, of the crater evidently formed by the fatal impact. Known today by the arresting if unpronounceable Mayan name Chicxulub, the crater straddles the coast of the Yucatan peninsula in Mexico. It is buried deep under hundreds of feet of sediment and measures more than 125 miles in diameter. (Estimates of its exact size vary, depending on how researchers read the deviations in local gravitational and magnetic field lines used to map it.)
The story of its discovery begins in the early 1970's, when Walter Alvarez was puzzling over the composition of a layer of rocks he'd chipped away in a gorge in Italy, near the city of Gubbio. The stratum dated back 65 million years, to the time when the long-glorious dinosaurs had suddenly disappeared. Oddly, it was rich in iridium, an element rare on Earth but common in comets and asteroids. Walter and Luis Alvarez pondered the matter for a year, then came up with the notion that the iridium had been splashed all over the planet by a killer impact. Their theory made headlines but scandalized many geologists who saw in it an unwelcome resurgence of catastrophism, the creationist doctrine that science had been obliged to defeat in the course of establishing gradual, long-term change as the engine behind Darwinian evolution.
The first test was to see whether the iridium was merely local or was to be found in strata of the same antiquity around the world, as would be expected had it been ejected by an enormous impact. This test the theory survived: strata excavated in Spain, Denmark, New Zealand and on the Pacific floor north of Hawaii yielded abnormally high iridium concentrations, as well as the 'shocked quartz,' globules, grains of soot and tiny spheres of fused silicates characteristic of an impact. Then geologists traced the ghostly outlines of the buried Chicxulub crater, and the Alvarez theory became so widely accepted that the menace of death from above is now part of popular lore. This year alone, it has been the subject of at least three televised documentaries and a television movie, 'Asteroid.'
As its tongue-in-cheek title suggests, 'T. Rex and the Crater of Doom' gets the facts across in a lighthearted, almost playful manner. But it's also solid science, a clear and efficient exposition that conveys plenty of cogent detail while keeping an eye on the subtle interplay of thought, action and personality that makes scientific research such arresting human behavior.
A good example is Mr. Alvarez's discussion of two riddles encountered by scientists investigating the global distribution of iridium and other debris thought to have been excavated by the Chicxulub impact. First, more shocked-quartz impact debris was found west of the crater -- in sediment cores taken from the Pacific Ocean floor -- than at the same distance to the east. This seemed very strange, but the solution turned out to be forehead-slappingly simple: the Earth's rotation had carried the impact site eastward while the debris was lofting high up and falling back down again, so that most of the stuff landed to the west of the crater. In a classic case of blinkering caused by knowing too much, the experts were delayed in hitting on the answer because most of them had learned about cratering by studying the moon, which rotates too slowly (only once every 28 days) to display any such effect.
The other riddle was that in the Western United States two kinds of ejecta -- shocked quartz and melted rock -- are not intermingled but segregated: the quartz is layered just above the melted rock. This could be explained if the quartz had been blown away from the impact site at a steeper angle than the melted ejecta, as the solution to the first puzzle also required. But twin patterns seemed to imply twin impacts from just one crater. How could that have happened?
Mr. Alvarez and a colleague, Philippe Claeys, consulted an impact dynamics expert, Susan Kieffer, who was then visiting Berkeley and who had 'studied all kinds of fast moving geologic processes,' Mr. Alvarez writes. 'Sue is a fine musician, and she once told me that the slow passages labeled adagio always bored her -- she likes her music presto or allegro molto vivace, and she likes geologic processes that move fast.' Mr. Alvarez and Mr. Claeys told her that they could explain both the 'shocked quartz pattern and the double ejecta layer if there was some way to launch the quartz on steeper trajectories than those of the melt droplets.' Her answer? The Chicxulub region is rich in limestone, which when vaporized would have released an enormous cloud of carbon dioxide. 'There must have been not one, but two gaseous fireballs -- the first a cloud of extremely hot, vaporized rock, and the second a cloud of CO2 vapor at a less elevated temperature, given off by more lightly shocked limestone,' Mr. Alvarez explains. Two fireballs, two patterns of debris fallout. 'It was satisfying to see details of the impact event fall into place so neatly.'
It is also satisfying to read about it, both in detail and in broad, confident generality, in this estimable account from the world's leading authority on death from above.
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Timothy Ferris is an emeritus professor of journalism at the University of California, Berkeley. His latest book is 'The Whole Shebang: A State-of-the-Universe(s) Report.'
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