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Geomorphology in the tropics: A study of weathering and denudation in the low latitudes
348
Book Reviews
the P loading at a regional scale and investigates the relative importance of point and non-point sources of P pollution to P loading. Herodek et al. discuss P cycling in the Balaton catchment in Hungary, and Kedziora et al. present the results of a study of P retention and transport in a riparian meadow. These studies are dispersed through the second half of the volume and act as a refreshing respite from the literature reviews when reading the volume straight through. A few weaknesses of the work do exist. The major weakness in my mind is the near total lack of discussion of unmanaged ecosystems. There is only one chapter in the volume that focuses on a nonagricultural site (Salcedo and Medeiros). In the final chapter of the volume, Salcedo and Medeiros discuss P transfer from terrestrial to aquatic systems with an emphasis on tropical mangrove ecosystems. The volume could have been strengthened and perhaps appealed to a larger audience if chapters discussing the cycling and transfer of P in Arctic tundra and temperate forests had been included. The book also contains a noticeable number of typographical errors that distract the reader. In summary, the subjects covered in the volume are particularly relevant to agronomists, biogeochemists, and fresh and salt water ecologists. However, geomorphologists with an interest in biogeochemistry will find this book useful. Although, those seeking a discussion of how the geomorphology of watersheds influences transfers and cycling of P may find this volume lacking. The lack of a geomorphological component to the work presented in this volume likely represents the lack of knowledge available about how land use patterns and land forms control the cycling and transfer of P. Tiessen acknowledges this fact in his introduction and synthebesis chapter stating “the intricate relationships tween land use patterns, surface and subsurface transport of P, and aquatic P loads are only now being explored.” Therefore, those interested in such issues will have to wait until such explorations are complete. D.M. Cairns Columbia, SC PII SO169-555X(96)00035-9
Geomorphology in the Tropics: A Study of Weathering and Denudation in the Low Latitudes. M.F. Thomas. Wiley, New York, 1994. 460 pp. ISBN o-47 1-93035-O.
There is little question that geomorphology is different in the tropics, at least to those who have worked in both tropical and extra-tropical regions. Defining these tropical peculiarities, however, is not so obvious. A list of geomorphic themes related to the tropics obviously spreads geographically to other latitudes and temporally to changing climates over the last 100 My. Therefore to deal with tropical geomorphology, a book must cover the known and possible processes and forms associated with the tropics and the best evidence for climatic change over the time scales of geomorphic evolution. Some topics clearly tropical are coral reefs, mangrove shores, intense weathering, tropical karst, rates and types of denudation, among many others. The prospects for writing such a book are imposing. The literature comes from many different languages and disparate fields that publish in a wide array of publications. Generally, Geomorphology in the Tropics: A Study of Weathering and Denudation in the Low Latitudes by M.F. Thomas is an excellent attempt to cover many tropical themes as a coherent topic. This is a rich, mature source on tropical geomorphology, especially on weathering and denudation. The book draws from more than 1300 references (the bibliography is 44 pp.) and many years of the author’s experience in the field. The book is thoroughly illustrated with many black and white photos (and six pages of color photos), tables, diagrams, and equations. An eight-page author index and a 17-page subject index are very accurate and helpful for using this book as a reference. Indeed, this book is an ideal reference for all geomorphologists, geoarchaeologists, and environmental scientists who work in the tropics. The author always provides clear, measured, and critical reviews of these topics. Fine examples include his reviews of carbonate dissolution and rates of karst development in tropical versus temperate environments in Chapter 2 and etchplanation in Chapter 7. The Preface and Introduction make the case for tropical geomorphology and its unjust negligence,
Book Reviews
and then progress into a concise overview of climatic geomorphology and the historical themes in tropical geomorphology. After the introduction, the book is logically organized into four parts: weathering; denudation; quatemary environmental change; and evolution of landforms. Chapter 2 sets the tone of the primacy of weathering as a distinguishing feature of the tropics. Here the book describes the influences of temperature and precipitation, the evidence for hydrothermal alteration of weathering profiles, and outlines the dominant weathering processes of the tropics. This chapter end:s by discussing the difficulty in estimating rates of weathering; some high estimated rates are simply not fsupported by the wide presence of deep saprolites or offshore sedimentary volumes. Chapter 3 examines the formation of weathering profiles and saprolites in terms of the many factors of weathering and in many different landscapes. A general criticism of this book could be its negligence of human uses of and impacts on tropical geomorphology, though Ch,apter 3 does conclude with a section on the importance of weathered rocks as a source for groundwater in sub-humid regions. Chapter 4 builds the previous discussions of processes into a discussion of the formation of laterites (and ores such as auriferous laterites), bauxites, and duricrusts. The author explains duricrusts in terms of the major factors of their formation, the general CLORPT model of Jenny plus paleoenvironmental changes, E, and pH conditions, and ground water hydrology. The last section of the chapter briefly outlines duricrusts, but neglects the wide area of calcretes in the northem Yucatan. Part II includes two chapters about denudation Processes in processes, curiously titled Su$uce Tropical Climates and Landsliding and Other Mass Movement. The former chapter treats the processes and rates of geologic and accelerated erosion starting from tropical rainfall to infiltration, pipe flow, influences of clay mineralology, runoff, sediment yields, rates of accelerated erosion, many aspects and examples of gully erosion, and finally to fluvial erosion and chemical denudation. There is little treatment of the causes of accelerated soil erosion and geomorphological contributions to soil conservation, though Table 5.6 does provide a list of the remarkably high reported rates of erosion in the tropics. A similar conclusion can be d:rawn about chapter 6 on mass
349
movements; yet, both of these sections are generally careful overviews of these broad topics. Part III shifts into geomorphic change in the context of Quatemary environments. Chapter 7 outlines the evidence for changing Quatemary environments, and Chapter 8 discusses specific landforms associated with environmental change. Chapter 7 is a thorough assessment, weighing the forms of evidence and the concepts of tropical paleoecology such as glacial-interglacial cycles, dating, fossils, biogeographic evidence, refugiu, Milankovich cycles, Heinrich events, empirical evidence, and climate modeling. One lacuna in this chapter and indeed in the whole book is its oversight of Central America. Central America is mentioned, but much of the important research in the Peten, Yucatan, and Costa Rica is not considered. On the other hand, two exemplary attributes of this book are embodied in Chapter 8: the focus on many practical case studies such as placer formation and the consistent attempt to compare different lines of evidence such as paleoecological and geomorphic. Part IV examines the evolution of tropical landscapes from etchplains in Chapter 9 to erosional terrain in Chapter 10 to long-term evolution in the final chapter. Chapter 9 is a long assessment of the evolution of the concept of etchplains and the processes of their formation, leading finally to an integrative theory of etchplanation. This chapter alone is a very good place to start learning about this concept because of its thorough discussion reflecting diverse literature, excellent illustrations, and comparisons with the development of other concepts such as peneplains and pediplains. Chapter 9 progresses rationally to discussions of residual forms, including a diversity of inselbergs and karst features, and longterm landscape evolution. Throughout the book are numerous elegant black-and-white diagrams and photographs, and this is especially true of Chapter 10. The final chapter is a fair and integrative overview that places tropical geomorphology in the big picture of the last 100 My. A few objections about this book include a lack of discussion and references about Central American topics such as coastal karst features like Blue Holes, the tropical rendolls (mollisolls) and carbonate weathering of Yucatan, and the paleoecology of the Pet&r. It is also worth mentioning that there is
350
Book Reviews
insufficient consideration of archaeological literature and humans as geomorphic agents. Admittedly, however, I read most of this book while conducting geoarchaeology research in Belize and Guatemala studying the impacts of the Ancient Maya. One last criticism is a lack of up-to-date soil references (on soil erosion, formation, weathering, etc.) from the United States, which represents a large under tapped source of information. These are small criticisms, and all-in-all this was an enriching book to read. It was very well edited, exceptionally illustrated, and logically organized. For any geomorphologist or earth scientist who works in the tropics, this is a necessary reference. It would also be ideal for upper division or graduate-level courses on tropical geomorphology. The book emphasizes weathering and denudation, which permits little room for discussion of coral reefs and mangrove coasts (two of the most recognized topics in tropical geomorphology). These topics are covered adequately elsewhere and would only diminish the book’s focus. Therefore, this is a logically coherent book for weathering and denudation in the low latitudes. T. Beach Washington, DC PII SO169-555X(96)00036-0
Theory of Rejlectance and Emittance Spectroscopy. B. Hapke. Cambridge University Press, Cambridge, 1993. Topics in Remote Sensing 3, 455 pp. Remote Geochemical Analysis: Elemental and Mineralogical Composition. C.M. Pieters and P.A.J. Englert (Editors). Cambridge University Press, Cambridge, 1993. Topics in Remote Sensing 4, 594 pp. This review discusses two books in the series Topics in Remote Sensing published by Cambridge University Press in 1993. The first text is a theoretical introduction to reflectance and spectroscopic analysis authored by Bruce Hapke. The second work, edited by Carl6 Pieters and Peter Englert, is a compendium of theory, techniques, and applications of remote geochemical analysis. This article reviews both books as independent works.
Theory of Reflectance
and Emittance
Spectroscopy
The motivation for Hapke to present this theoretical text is to provide tools enabling planetary scientists to describe and evaluate characteristics of the surfaces they study. Presented via a progression of theoretical models, the text provides numerous formulas and references for models which may be used by planetary and earth system scientists, particularly those interested in remote sensing. For geomorphologists seeking to use remote sensing, the theoretical underpinnings of the science are rigorously illuminated through mathematical equations. The theory and application is decidedly oriented toward the theory behind biophysical remote sensing rather than common methods of image enhancement and classification. The book is aimed at advanced undergraduates and beginning graduate students in the physical sciences and requires a background in physics and ample proficiency in calculus. Brief mathematical reviews are also included in appendices. Following an introduction, the book provides background on electromagnetic-wave propagation theory, commencing with Maxwell’s equations. Chapter 3 introduces absorption of electromagnetic radiation in liquids and solids. Chapter 4 describes specular reflectance and associated refraction, single particle scattering, and particularly Mie and Rayleigh scattering as they are referred in remote sensing. Chapter 7 introduces equations of radiative transfer and provides discussion of nonuniform scatterers. Approximate solutions for radiative transfer equations and exact expressions for several kinds of reflectances are given in Chapters S-10. Chapter 8 provides a succinct and clear description of geometrical reflectance, particularly directional and hemispherical reflectance. Empirical relations are reviewed, as are Lambert’s and Minnaert’s Laws. Bidirectional reflectance is described and approximately demonstrated and mathematically solved for different scatterers. For example, the opposition effect, or shadow-hiding relating to phase angles and particle sizes and wavelengths, is clearly described. These issues are woefully represented in many remote sensing texts. Hapke soundly fills in details and assumptions that are bypassed or only briefly noted in standard remote sensing texts. Chapter 10 treats reflectances and quantities using
Book Reviews
the P loading at a regional scale and investigates the relative importance of point and non-point sources of P pollution to P loading. Herodek et al. discuss P cycling in the Balaton catchment in Hungary, and Kedziora et al. present the results of a study of P retention and transport in a riparian meadow. These studies are dispersed through the second half of the volume and act as a refreshing respite from the literature reviews when reading the volume straight through. A few weaknesses of the work do exist. The major weakness in my mind is the near total lack of discussion of unmanaged ecosystems. There is only one chapter in the volume that focuses on a nonagricultural site (Salcedo and Medeiros). In the final chapter of the volume, Salcedo and Medeiros discuss P transfer from terrestrial to aquatic systems with an emphasis on tropical mangrove ecosystems. The volume could have been strengthened and perhaps appealed to a larger audience if chapters discussing the cycling and transfer of P in Arctic tundra and temperate forests had been included. The book also contains a noticeable number of typographical errors that distract the reader. In summary, the subjects covered in the volume are particularly relevant to agronomists, biogeochemists, and fresh and salt water ecologists. However, geomorphologists with an interest in biogeochemistry will find this book useful. Although, those seeking a discussion of how the geomorphology of watersheds influences transfers and cycling of P may find this volume lacking. The lack of a geomorphological component to the work presented in this volume likely represents the lack of knowledge available about how land use patterns and land forms control the cycling and transfer of P. Tiessen acknowledges this fact in his introduction and synthebesis chapter stating “the intricate relationships tween land use patterns, surface and subsurface transport of P, and aquatic P loads are only now being explored.” Therefore, those interested in such issues will have to wait until such explorations are complete. D.M. Cairns Columbia, SC PII SO169-555X(96)00035-9
Geomorphology in the Tropics: A Study of Weathering and Denudation in the Low Latitudes. M.F. Thomas. Wiley, New York, 1994. 460 pp. ISBN o-47 1-93035-O.
There is little question that geomorphology is different in the tropics, at least to those who have worked in both tropical and extra-tropical regions. Defining these tropical peculiarities, however, is not so obvious. A list of geomorphic themes related to the tropics obviously spreads geographically to other latitudes and temporally to changing climates over the last 100 My. Therefore to deal with tropical geomorphology, a book must cover the known and possible processes and forms associated with the tropics and the best evidence for climatic change over the time scales of geomorphic evolution. Some topics clearly tropical are coral reefs, mangrove shores, intense weathering, tropical karst, rates and types of denudation, among many others. The prospects for writing such a book are imposing. The literature comes from many different languages and disparate fields that publish in a wide array of publications. Generally, Geomorphology in the Tropics: A Study of Weathering and Denudation in the Low Latitudes by M.F. Thomas is an excellent attempt to cover many tropical themes as a coherent topic. This is a rich, mature source on tropical geomorphology, especially on weathering and denudation. The book draws from more than 1300 references (the bibliography is 44 pp.) and many years of the author’s experience in the field. The book is thoroughly illustrated with many black and white photos (and six pages of color photos), tables, diagrams, and equations. An eight-page author index and a 17-page subject index are very accurate and helpful for using this book as a reference. Indeed, this book is an ideal reference for all geomorphologists, geoarchaeologists, and environmental scientists who work in the tropics. The author always provides clear, measured, and critical reviews of these topics. Fine examples include his reviews of carbonate dissolution and rates of karst development in tropical versus temperate environments in Chapter 2 and etchplanation in Chapter 7. The Preface and Introduction make the case for tropical geomorphology and its unjust negligence,
Book Reviews
and then progress into a concise overview of climatic geomorphology and the historical themes in tropical geomorphology. After the introduction, the book is logically organized into four parts: weathering; denudation; quatemary environmental change; and evolution of landforms. Chapter 2 sets the tone of the primacy of weathering as a distinguishing feature of the tropics. Here the book describes the influences of temperature and precipitation, the evidence for hydrothermal alteration of weathering profiles, and outlines the dominant weathering processes of the tropics. This chapter end:s by discussing the difficulty in estimating rates of weathering; some high estimated rates are simply not fsupported by the wide presence of deep saprolites or offshore sedimentary volumes. Chapter 3 examines the formation of weathering profiles and saprolites in terms of the many factors of weathering and in many different landscapes. A general criticism of this book could be its negligence of human uses of and impacts on tropical geomorphology, though Ch,apter 3 does conclude with a section on the importance of weathered rocks as a source for groundwater in sub-humid regions. Chapter 4 builds the previous discussions of processes into a discussion of the formation of laterites (and ores such as auriferous laterites), bauxites, and duricrusts. The author explains duricrusts in terms of the major factors of their formation, the general CLORPT model of Jenny plus paleoenvironmental changes, E, and pH conditions, and ground water hydrology. The last section of the chapter briefly outlines duricrusts, but neglects the wide area of calcretes in the northem Yucatan. Part II includes two chapters about denudation Processes in processes, curiously titled Su$uce Tropical Climates and Landsliding and Other Mass Movement. The former chapter treats the processes and rates of geologic and accelerated erosion starting from tropical rainfall to infiltration, pipe flow, influences of clay mineralology, runoff, sediment yields, rates of accelerated erosion, many aspects and examples of gully erosion, and finally to fluvial erosion and chemical denudation. There is little treatment of the causes of accelerated soil erosion and geomorphological contributions to soil conservation, though Table 5.6 does provide a list of the remarkably high reported rates of erosion in the tropics. A similar conclusion can be d:rawn about chapter 6 on mass
349
movements; yet, both of these sections are generally careful overviews of these broad topics. Part III shifts into geomorphic change in the context of Quatemary environments. Chapter 7 outlines the evidence for changing Quatemary environments, and Chapter 8 discusses specific landforms associated with environmental change. Chapter 7 is a thorough assessment, weighing the forms of evidence and the concepts of tropical paleoecology such as glacial-interglacial cycles, dating, fossils, biogeographic evidence, refugiu, Milankovich cycles, Heinrich events, empirical evidence, and climate modeling. One lacuna in this chapter and indeed in the whole book is its oversight of Central America. Central America is mentioned, but much of the important research in the Peten, Yucatan, and Costa Rica is not considered. On the other hand, two exemplary attributes of this book are embodied in Chapter 8: the focus on many practical case studies such as placer formation and the consistent attempt to compare different lines of evidence such as paleoecological and geomorphic. Part IV examines the evolution of tropical landscapes from etchplains in Chapter 9 to erosional terrain in Chapter 10 to long-term evolution in the final chapter. Chapter 9 is a long assessment of the evolution of the concept of etchplains and the processes of their formation, leading finally to an integrative theory of etchplanation. This chapter alone is a very good place to start learning about this concept because of its thorough discussion reflecting diverse literature, excellent illustrations, and comparisons with the development of other concepts such as peneplains and pediplains. Chapter 9 progresses rationally to discussions of residual forms, including a diversity of inselbergs and karst features, and longterm landscape evolution. Throughout the book are numerous elegant black-and-white diagrams and photographs, and this is especially true of Chapter 10. The final chapter is a fair and integrative overview that places tropical geomorphology in the big picture of the last 100 My. A few objections about this book include a lack of discussion and references about Central American topics such as coastal karst features like Blue Holes, the tropical rendolls (mollisolls) and carbonate weathering of Yucatan, and the paleoecology of the Pet&r. It is also worth mentioning that there is
350
Book Reviews
insufficient consideration of archaeological literature and humans as geomorphic agents. Admittedly, however, I read most of this book while conducting geoarchaeology research in Belize and Guatemala studying the impacts of the Ancient Maya. One last criticism is a lack of up-to-date soil references (on soil erosion, formation, weathering, etc.) from the United States, which represents a large under tapped source of information. These are small criticisms, and all-in-all this was an enriching book to read. It was very well edited, exceptionally illustrated, and logically organized. For any geomorphologist or earth scientist who works in the tropics, this is a necessary reference. It would also be ideal for upper division or graduate-level courses on tropical geomorphology. The book emphasizes weathering and denudation, which permits little room for discussion of coral reefs and mangrove coasts (two of the most recognized topics in tropical geomorphology). These topics are covered adequately elsewhere and would only diminish the book’s focus. Therefore, this is a logically coherent book for weathering and denudation in the low latitudes. T. Beach Washington, DC PII SO169-555X(96)00036-0
Theory of Rejlectance and Emittance Spectroscopy. B. Hapke. Cambridge University Press, Cambridge, 1993. Topics in Remote Sensing 3, 455 pp. Remote Geochemical Analysis: Elemental and Mineralogical Composition. C.M. Pieters and P.A.J. Englert (Editors). Cambridge University Press, Cambridge, 1993. Topics in Remote Sensing 4, 594 pp. This review discusses two books in the series Topics in Remote Sensing published by Cambridge University Press in 1993. The first text is a theoretical introduction to reflectance and spectroscopic analysis authored by Bruce Hapke. The second work, edited by Carl6 Pieters and Peter Englert, is a compendium of theory, techniques, and applications of remote geochemical analysis. This article reviews both books as independent works.
Theory of Reflectance
and Emittance
Spectroscopy
The motivation for Hapke to present this theoretical text is to provide tools enabling planetary scientists to describe and evaluate characteristics of the surfaces they study. Presented via a progression of theoretical models, the text provides numerous formulas and references for models which may be used by planetary and earth system scientists, particularly those interested in remote sensing. For geomorphologists seeking to use remote sensing, the theoretical underpinnings of the science are rigorously illuminated through mathematical equations. The theory and application is decidedly oriented toward the theory behind biophysical remote sensing rather than common methods of image enhancement and classification. The book is aimed at advanced undergraduates and beginning graduate students in the physical sciences and requires a background in physics and ample proficiency in calculus. Brief mathematical reviews are also included in appendices. Following an introduction, the book provides background on electromagnetic-wave propagation theory, commencing with Maxwell’s equations. Chapter 3 introduces absorption of electromagnetic radiation in liquids and solids. Chapter 4 describes specular reflectance and associated refraction, single particle scattering, and particularly Mie and Rayleigh scattering as they are referred in remote sensing. Chapter 7 introduces equations of radiative transfer and provides discussion of nonuniform scatterers. Approximate solutions for radiative transfer equations and exact expressions for several kinds of reflectances are given in Chapters S-10. Chapter 8 provides a succinct and clear description of geometrical reflectance, particularly directional and hemispherical reflectance. Empirical relations are reviewed, as are Lambert’s and Minnaert’s Laws. Bidirectional reflectance is described and approximately demonstrated and mathematically solved for different scatterers. For example, the opposition effect, or shadow-hiding relating to phase angles and particle sizes and wavelengths, is clearly described. These issues are woefully represented in many remote sensing texts. Hapke soundly fills in details and assumptions that are bypassed or only briefly noted in standard remote sensing texts. Chapter 10 treats reflectances and quantities using