User:Bruce Bathurst

Bruce Bathurst

Bruce Bathurst was a geologist.

Interests

His interests include general geology, petrology, classical thermodynamics, philosophy, mathematics, perennial gardening, handling rocks & old books, and grinding coffee.

Views affecting Wikipedia entries

Bruce's master's & doctoral theses offered new theorems in equilibrium thermodynamics and applied these to igneous & metamorphic petrology. His most satisfying subject is the application of thermodynamics to petrology, and for this he reads principally in the physical & chemical literature published in Europe during the late 19th Century. Bruce believes that much of current petrologic theory is an interpretation of classical thermodynamics (unstable, metastable, & stable local equilibrium). Bowen's reaction series and Eskola's mineral classification, Bruce believes found igneous & metamorphic petrology, respectively; and he sees these as thermodynamic theorems. These, and the theorems' geometrical interpretations, strongly influence Bruce's points of view.

Education

Bruce was educated in the United States. His interests strayed little from his courses as an NSF Fellow when 17-years old, at the Colorado School of Mines, in Golden, Colorado: geology, thermodynamics, & the philosophy of science. After receiving a diploma in geology from the Mackay School of Mines, in Reno, Nevada, Bruce spent a year studying in Germany and France. That spring, he examined all the sites in E.B. Bailey's Tectonic Essays, mainly Alpine. Bruce's graduate degrees are fromDartmouth College, in New Hampshire, and Princeton University, in New Jersey, where he ended his academic experiences again as an NSF Fellow. These institutions, however, in no way share his opinions (or will likely agree with him on the color of an orange).

Field Areas

Bruce mapped for mining companies, universities, & for himself in the Central Sierra Nevada (US) of California, the lower Owens Valley of California, the Northern Central Valley (California), much of Western & Central Nevada, the Rocky Mountains in Colorado, the Black Forest of Germany, the Alps of Austria and of Switzerland, the Jura Mountains in France and Switzerland, active volcanos in Central America, White Mountains (New Hampshire), Green Mountains of Vermont, the Berkshire Mountains of Massachusetts, Adirondack Mountains of New York, and various regions in the Central Appalachians in New Jersey & Pennsylvania. Bruce also studied old field notebooks of selected geologists with the USGS in its archives near Denver, Colorado.

Bruce still owns his great-grandfather's vein-gold mine near Placerville, California, an area last mapped by Waldamir Lindgren (near the type area for 'granodiorite'). His study of such maps, while panning for gold, kindled an early interest in geology.

Geometrical Thermodynamics

A Geometrical Thermodynamics for Geologists

Because of the abundant evidence for local equilibrium in the Earth, and because metamorphic rocks have many thermodynamic phases, Bruce has long had an interest in thermodynamics. Equilibrium thermodynamics describes the states rocks attained (or strove to attain) with no knowledge of how they did this (the mechanisms chosen). Gneissose structure, for example, is easy to explain thermodynamically, though its mechanism isn't even guessed at. Thermodynamic theory (in turn) offers valuable, though unusual, kinds of information: predictions without explanations. States of local equilibrium preserved in rocks include stable, unstable, and the indifferent state (perhaps the most important and least studied). Bruce has classified thermodynamics geometrically, the geometry being determined by the axioms chosen.

Geometries allow pretty pictures of thermodynamics to be drawn, and they classify thermodynamics according to the abstractions of its data. Its projective geometry, for example, allows the orientation of paths to be more accurately delineated than simply crossing topological isograds. The projective path is related to a bundle of directions taken by the rock, relative to dT,d(-p), and dμ_i. Actual directions are treated by an affine geometry, and require more data than that visible in the field. (Topological isograds require identifying the minerals with a hand lens, projective sectors require the orientation of the final zoning measured with hand lens or petrographic microscope, & the path's direction from the relative magnitude of the zoning measured with a microscope or electron probe microanalyser.) This approch of classifying thermodynamics as a sequence of geometrical interpretations was taken because, as seen, the measures of decreasing abstractness correspond remarkably well with a similar sequence of measures made by geologists. It is also useful because geologists generally aren't familiar with how to extract useful conclusions from the more abstract measurements they routinely make.

Finally, by classifying thermodynamic quantities as intensities, densities, extensities, & energies, Bruce can describe the necessary and sufficient conditions for the validity of a theorem. Most texts must content themselves with drawing from large numbers of sets of data, making theorems sufficient only. One often sees, for example, a proof of the Clapeyron equation that tacitly assumes the system closed, yet it is claimed to apply to open systems. The proof offered only sufficient conditions. It is better, Bruce thinks, to write geometric proofs that offer both the necessary and the sufficient conditions for a theorem's application. Note that, when geometry rather than analysis is emphasized, the Clapyeron equation is written ΔSdT + ΔVd(-p) = 0: here the orientations (signs) of homogeneous tangent vectors aren't lost, as they are when the equation is written dp/dT = ΔS/ΔV.

The geometries are expressed in the languages of Grassmann, Klein, & Cartan.