American Chemical Society Talks


Biographical Sketch

Steven Dutch is a geologist who got his bachelors degree (and a ringside seat on the unrest of the 1960's) from the University of California at Berkeley . He did his doctoral research at Columbia University, with a break for military service that included a year in Turkey. The subject of his thesis was the geology of the Sudbury, Ontario area, but in 1975 he also participated in a Columbia expedition to Antarctica . Since 1976 he has been at the University of Wisconsin at Green Bay, where he holds the rank of Professor, and where he teaches "hard rock " geology: mineralogy, petrology, structural geology and plate tectonics . His principal research interests are the Precambrian geology of the Great Lakes region, the development of computer programs for earth science education, and the relationships between science and society, particularly as expressed in pseudoscience movements. He is the author of an earth science textbook.

In 1982 Dr. Dutch resumed his military career by joining the 432nd Civil Affairs Battalion of the U.S. Army Reserve. He spent six months in the Persian Gulf and Kurdistan in 1991 and six months with the peacekeeping mission in Bosnia in 1996. In 1998 he participated in an 18-day Partnership for Peace mission to Bulgaria.

Dr. Dutch is married and has two sons. His wife Shawn is a caregiver and an instructor in deaf sign language and Spanish.

Previous ACS Tours

How did a Geologist end up as an ACS Speaker?

In 1986, a colleague asked me to do a talk for the local ACS section on some topic dealing with both chemistry and geology. I had just finished doing some reading on the formation of the Solar System, and developed a talk I called "Recipe for a Small Planet" (see abstract below.) It was a success, and my colleague suggested I submit the talk as an ACS tour talk. I also submitted several other topics and the rest is history. Although I am chemically literate, I'm not a research chemist. On the other hand, my audiences typically have little acquaintance with earth and planetary science. I view my role as providing some hopefully entertaining and interesting ideas that cross the borders of both disciplines.

A Scientist Goes to Desert Storm

Observations of scientific interest during the Persian Gulf war and Operation Provide Comfort in Kurdistan. Includes views of the oil fires, effects of modern weapons, and public health problems in refugee operations. Also includes a few scenes of scientific interest from Bosnia in 1996.

Why Minerals Are Colored

In the past two decades spectacular progress has been made in understanding why minerals and materials in general display the colors they do. The simplest mechanisms to understand are those involving physical optics: scattering (snow, blue sky, milky quartz), dispersion (rainbows and fire in gems), diffraction (peacock feathers, butterfly wings, and opal) and thin-layer interference (oil films, mother-of-pearl, iridescent tarnish).

Ionic crystals owe their colors to crystal-field mechanisms. The red of ruby and the green of emerald are both due to chromium impurities! Other substances get their color from electron interactions between atoms: molecular orbitals (organic dyes) or charge transfer (chromate compounds). Metals and semiconductors owe their colors to the existence of energy bands. In a metal, any visible photon can find an electron to excite; thus metals tend to be opaque and highly reflective across the entire visible spectrum. In a semiconductor, there is an energy gap between the energy levels of the valence electrons and the energy levels that can be occupied by free electrons. If the energy gap is greater than the energy of any visible photon, the material will be transparent (diamond) A slightly smaller gap will absorb the blue end of the spectrum but transmit red and yellow (sulfur). Very small gaps will absorb all visible wavelengths (galena). Impurities may help bridge the energy gap (blue diamond).

Beware the Pseudoscientist

There is a vast industry in the United States that is engaged in the manufacture and dissemination of scientific misinformation . Pseudoscience, or ideas that claim scientific validity but are demonstrably faulty finds an audience for a variety of reasons . Some beliefs (diet fads) promise easy solutions to otherwise intractable problems. Others (creationism, psychic research, UFO beliefs) either are aimed directly at supporting a specific religious dogma or serve as substitutes for religion. Many beliefs (Bigfoot) seem mostly intended to titillate and lend a little excitement to life. Many beliefs (Laetrile in particular) seem to serve as a focus for discontent. Virtually all pseudoscientific theories have elements of the anti-authoritarianism that fueled the Laetrile campaign of the 1970's.

The best defense against pseudoscience is scientific literacy but there are useful clues the non-scientist can look for. Almost all pseudoscience has a touch of paranoia; the single best clue is any allegation of conspiracy or persecution. Other common aspects of pseudoscience are exaggeration of uncertainties in science, extreme relativism, overly complex approaches to otherwise simple problems, logical fallacies, and distortion of credentials.

Pseudoscience is not merely an irritating fad. It has created an environment in which faulty reasoning is deemed scientifically legitimate, pseudoscientists attain the status of experts, and where many Americans literally have no idea what is true on subjects like evolution or psychic research.

Recipe for a Small Planet

Starting from the assumption that the Solar System formed from a cloud of matter with the same overall composition as the Sun, it is possible to explain a great deal of Solar System chemistry in fairly simple terms. Hydrogen and helium, which make up over 99 per cent of the Sun, would not accrete to form solid particles. The remaining elements, called "metals" by astronomers, are represented in approximately solar abundances in a class of meteorites called carbonaceous chondrites, which are believed to be the most primitive material in the Solar System. In the warm inner Solar System, solid grains would be predominately iron-nickel, iron sulfides, and iron and magnesium silicates, materials which make the inner planets. In the cold outer Solar System, water-ice would form in addition. Most lunar rocks can be explained broadly in terms of differentiation of primitive Solar System material. The granitic continental crust of the earth, rich in potassium and aluminum is much harder to explain and reflects a long history of chemical differentiation.

The Violent Birth of Planet Earth

Ideas on the formation of the Earth have literally run hot and cold. Initially, it was generally assumed that the Earth must have formed very hot in order to account for its present internal heat. Lord Kelvin's famous attempts to calculate the age of the Earth on physical grounds made use of this assumption. Even though the discovery of radioactivity in 1896 furnished an alternative source of heat for the Earth, the assumption of a hot beginning lingered for decades. Two celebrated images of the early hot Earth are a legacy from that era: Walt Disney's Fantasia and Chesley Bonestell's dramatic image published in Life magazine.

It was not until well into this century that astronomers realized that an accreting Earth need not have formed hot, and between about 1940 and 1960 there were a number of advocates of a cool formation for the Earth. However, as more was learned about the physics of impact and planetary accretion, it became clear that the hot-origin picture was in fact correct. Lunar rock samples indicate that the crust of the Moon was once molten, and theoretical studies suggest that the later stages of planetary accretion result in enough heat buildup to create magma oceans on the surfaces of new planets. More recently, theoretical studies suggest that the final stages of Solar System accretion may have involved planetary-scale impacts sufficient to melt much of the impacting bodies. A mega-impact formation of the Earth-Moon system avoids most of the difficulties that had plagued previous theories.


No doubt about it - impact is in. The dreadful TV movie Asteroid and the scientifically somewhat more accurate films Armageddon and Deep Impact, the idea that an asteroid impact led to the extinction of the dinosaurs, plus the media buzz surrounding asteroid 1997 XF11, have raised public awareness and interest in meteor impact to all-time highs.

It took a long time for scientists to accept the reality of meteor impact. Meteor craters are rare on Earth and usually highly modified. Right up until the Apollo era there were still scientists that argued that lunar craters were volcanic in origin. But field studies on the Earth and Moon and imagery of other planets has given us a fairly clear idea of what happens during large impacts. The forces involved in a large impact defy imagination; they so far exceed the yield strength of any rock that rocks are pushed aside as if they had no strength whatever. The best small-scale models for impact phenomena, amazingly, are slow-motion and strobe photographs of drops splashing.

Walter Alvarez' discovery of the iridium anomaly at the Cretaceous-Tertiary boundary was a superb example of serendipity in science. He was collecting samples of iron-bearing limestone for paleomagnetic studies to track the movements of small plates in the Mediterranean when he noticed a single clay layer in the limestone. He realized that something had shut down biological productivity for a while, exactly at the Cretaceous-Tertiary boundary, and had the clay analyzed for iridium in an attempt to measure the duration of the hiatus. He had hoped to use iridium as a tracer of micrometeorite flux, but the iridium content was so large he realized that the clay must mark a major impact. Dinosaurs were about the farthest thing from his mind when he made the initial discovery.

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Created 28 May 1998, Last Update 31 August 1998

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