Heat Transport and Energetics of the Earth and Rocky Planets
The chemical and thermal evolution of the Earth is actively debated and is of great interest to natural scientists. Heat flow in large bodies being linked to material properties, energy inventories, and mass flow is central to this problem, and is a major focus of this book. Because heat flow depends on time and space, the initial conditions are very important: The gravitational processes that formed the Solar System remain relevant today. Because much is unknown, comparing Earth to other rocky planets with ancient surfaces is very useful. Moreover, such comparisons highlight Earth’s unique behavior. Critical analysis of old observations and considering recent data on heat transfer and melting of planetary materials led us to revise the geotherm, propose a new mechanism for plate tectonics, and postulate a novel origin of chondritic meteorites. This book also provides new calculations of the thermal structure of Earth’s interior that are based on real material properties.
The theoretical basis for this treatment is presented in our recently published book “Measurements, Mechanisms, and Models of Heat Transport,” which covers heat flow on microscopic scales and in the laboratory. Motion of heat in large bodies involves additional, macroscopic mechanisms. Body size matters for reasons other than cooling time frames. Distance and mass govern gravitational forces, which generally oppose thermal forces such as buoyancy, and created the axial spin of planets. The effect of self-gravitation on the thermal state of the Earth has been misunderstood because gravity is not considered in classical thermodynamics. Neither has the effect of length-scales on heat transport received sufficient attention, yet the physical property of thermal diffusivity and Fourier’s second equation relate temperature to the lumped combination of length and time. Lastly, today’s view of the Earth as a whole is mostly garnered from numerical models. Important observations have been short-shifted, despite these being numerous and constraining. In addition, some historical relics impede progress: for example, Kevin’s dis-proven concept that contraction produces starlight still exists in the faulty notion that planetary core formation releases enormous amounts of heat.
To better understand the interior of the Earth (which is a moderately hot, evolving, and self-gravitating body) requires addressing the above issues and others. Although much relevant material exists, it is scattered among the literature of diverse fields, including materials science, geoscience, planetary science, and astronomy. This disorganization has caused key links to be overlooked, which has fostered misunderstandings and precluded the development of a coherent picture. Moreover, recent discoveries regarding microscopic behavior, which are the focus of “Measurements, Mechanisms, and Models of Heat Transport,” have not been applied to geophysical problems.
The present book develops new concepts that reconcile available data with physical principles using analytical mathematics, while recognizing that the interiors of Earth and other rocky bodies are mostly hidden from view. In reviewing the literature for the book and over the past several years, we were quite surprised at the large number of inconsistencies between observations and many current models in geophysics, planetary science, and related fields. These inconsistencies appear to be stem from overspecialization, overextension, and placing too much trust on ideas developed hundreds of years ago when data were few and uncertain. Concepts in the book are based on what is truly known rather than on what is inferred or believed.
The book is organized in 3 parts. Part I presents relevant observations on the Earth which is the best constrained planet and the focus of the book. Processes that move heat on small and large scales are covered, and the large energy reservoirs generated by radio-nuclides, axial spin, and externally imposed gravitational forces are evaluated. Mathematical formulations useful for analyzing bodies of diverse size are included. We explain how the core formed first, due to magnetic interactions, friction welding, and cold welding. We propose that motions of the tectonic plates are driven by the 3-dimensional, time-dependent, gravitational configuration of the Moon-Earth-Sun system. We address why plate tectonics is unique to the Earth. Our proposal is based on the reality that gravitational forces, not heat, are responsible for practically all large-scale motion in the universe. Although the focus is on the behavior of Earth’s interior, much of the discussion in Part I is general.
Part II delves into the current thermal state of the Earth by combining models and observations. It critically reviews existing paradigms, many of which are based on problematic mathematics. This part is organized from Earth’s surface down, because the outermost layers are the best constrained. Whereas the continental crust can be treated as 1-dimensional, the oceanic crust is a 2-dimensional feature, and the mantle and core must be treated in spherical coordinates. Hence, these regions are treated in separate chapters.
Part III first discusses the thermal history of Earth, and continues in a separate chapter that compares Earth to the other rocky bodies of the Solar System, including the Moon. This chapter completes the picture of heat flow in large rocky bodies while exploring examples of what the Earth is not. The smallest bodies, chondrules, are covered separately to constrain the initial conditions, which set the stage for thermal evolution. The final chapter summarizes.
The quality and clarity of the book were substantially improved by review. Most chapters were critically reviewed by Bob Criss (Washington University, St. Louis), who is co-author on several. Both Bob and Everett Criss (Panasonic Avionics, Inc., Irvine, CA) contributed many ideas and crucial discussion. Everett co-authored one of the most important chapters in the book, and alerted me to cold welding. Reinhardt Criss (Manufacturing Technology, Inc. South Bend, IN) suggested the likelihood of friction welding. Bob’s efforts on thermally modeling the continents and in comparing the terrestrial planets were essential to completing the book and providing its coherency.
Preparation of this book was supported by my active NSF grant EAR-1524495. However, the content of the book, the findings and opinions, are those of the authors, but not necessarily of NSF. Preparation was aided by the hard-working librarians Ryan Wallace and Clara McLeod at Washington U. Many websites are referenced per the suggestion of Genevieve Criss, chemistry teacher at Young Women’s College Preparatory High School, Rochester, NY. This work is based on two decades of work in heat transfer, and my longer career in spectroscopy, with a recent focus on gravitation and applications of physical principles to the Earth and planets, in collaboration with Bob and Everett Criss.
Much appreciation is also due to the staff at Elsevier, for guidance and patience. I thank Marisa LaFleur, the acquisition editor, for inviting me to contribute and for obtaining helpful reviews. Acquisitions editor Amy Shapiro helped in the subsequent stages. Special thanks are due to the developmental editors, Theresa Yannetty and Kelsey Connors, for encouragement and substantial efforts in bringing the book to the finish line. Narmatha Mohan helped with permissions. I thank the production team headed by Debasish Ghosh for the impressive appearance of the final product.
Lastly, the book provides alternative hypotheses to explain observations in the geologic sciences and related fields, especially where controversy exists. These ideas are all related to the flow of heat. Last but not least, I thank Gillian Foulger (University Durham, UK) and Warren Hamilton (Colorado School of Mines) for stimulating discussions and encouragement. We hope that the reader will be stimulated to think critically, and beyond what is proposed here.
Anne M. Hofmeister St. Louis, MO, United States
July 23, 2019
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