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  • Recognizing Earth's Antiquity—and That a Reliable Geohistory Could Be Developed through Study of Rocks and Fossils
  • Jason A. Lillegraven
Martin J. S. Rudwick . Bursting the Limits of Time: The Reconstruction of Geohistory in the Age of Revolution (Chicago: Univ. of Chicago, 2005). Pp. 708. 179 ills. $45. ISBN 0-226-73111-1

Scientific and philosophical questions related to the age of our planet and its life-forms were under active pursuit late in the eighteenth century. Prime among them were the processes of Earth's formation and later modification, the nature and antiquity of life, and just when and how humans came into the scene. Martin J. S. Rudwick has provided a work of superb scholarship on thought related to processes and implications of those grand issues. His discourse begins with the summer of 1787 and ends roughly thirty-five years later. That particular interval, which might be expected to equate with the duration of a single scientific career, saw the beginnings of geoscience's greatest revolution in thinking about the Earth and its life in terms of yielding an interpretable history.

To put the magnitude of that conceptual revolution into perspective, I will start my review with a simple list of geologically relevant concepts that virtually [End Page 81] any scientifically literate person of the early twenty-first century would take for granted. Professional geologists and paleontologists should know more of the details, but most items on the list constitute common knowledge that in many instances would seem to border on the absurdly obvious:

  1. 1. Fossil clams in mudstone and ancient plant remains in coal beds, respectively, have more to do with clams preserved in jars of alcohol and pressed volumes of modern plants than they do with quartz crystals and chunks of granite—and yet the fossils are integral components of the rocks, not extraneous to them.

  2. 2. The wealth of known fossils represents traces of past life covering a wide diversity of geologic ages, now understood to encompass billions of years. Human origins and subsequent history were continuous with, and an integral part of, geologic history. Earth history did not comprise a simple division into a brief human-dominated interval that was preceded by a much longer, prehuman interval—separated by a unique event (a "revolution"), such as a catastrophic deluge. An uninterrupted continuum in Earth and life history is clearly understood. "The Flood" did not emplace all fossil bones.

  3. 3. Although genuinely global catastrophes have punctuated Earth history, such as the meteoritic impact associated with extinctions at the end of the Cretaceous period, much of geologic time has been characterized by operation of familiar, locally observable processes related to weather, erosion, deposition, and influences of diverse life-forms similar in general form and function to those that affect our lives today.

  4. 4. Firsthand observation in the field, by the practicing scientist himself, is critically important to comprehending large-scale features of the Earth; they cannot be reliably understood from hypothetico-deductive models based upon assumptions derived from first-order principles of physics. Although carefully documented, field-based observations inevitably complicate theories developed by thinkers cozy by the fire, direct observations are essential to gaining true understanding. And we should not proceed by going into the field with the purpose of collecting confirmatory evidence to help prove our newly built conceptual models.

  5. 5. It is possible, through the interpretation of field-gained evidence, to document a reliable, stepwise history of Earth. This applies for times even before man existed to record what happened. The idea that Earth held no "meaning" prior to the time of human existence to provide it with meaning holds no scientific relevance.

  6. 6. Superpositional rock occurrences (with older strata generally underlying younger) represent useful geohistorical tools for recognizing relative antiquities of sedimentary rock units. [End Page 82]

  7. 7. The basic structures of rock folds, mountains, and basins are of importance beyond mining technology in that such structures also provide strong evidence about the sequence of deformational events and relative ages in the development of Earth. Detailed knowledge of the structures, involving the discipline formerly known as "geognosy" but now labeled "structural geology," is a fundamentally important part of Earth science.

  8. 8...


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