Climatic Geomorphology/ Geomorfologia climatica

Climatic Geomorphology/ Geomorfologia climatica

Климатическая геоморфология/ Klimatische Geomorphologie

Mateo Gutierrez

Climatic Geomorphology constitutes a new look at a fairly old subject that has been largely ignored in other more recent trends in the field, particularly in much process geomorphology. But now Mateo Guti6rrez, well-known Professor of Geomorphology at the University of Zaragoza in northeast Spain, has presented us with this new volume, translated into English by ten of his colleagues. We are fortunate indeed to have his authoritative writing and artful photography of so many parts of the world to grace our understanding of landform character and evolution. Originally published in Spanish in 2001, this volume attracted the notice of many other geoscientists and was reviewed quite favourably in more than five of our main journals of geomorphology, physical geography, and environmental geology. The uniform praise led to suggestions that a translation into English might be warranted, with the results that you now see before you. The relative lack of such modem and well-illustrated texts devoted to climatic geomorphology in the English language indicates that this new book is a deserving addition to the literature. In recent years the great interest in the climate change so obviously underway in the world, as well as the consequences of even greater climate change in the geological past, have led to considerable interest in the topic. This book provides a global overview of the different climatic zones of the Earth, and it reviews the advances in climatic geomorphology that have been achieved in the past decades. Certain landform assemblages are well known to be associated with different regional climate-process systems, a statement that underscores the obvious, despite the fact that the details of some climate- controlled processes are not yet that well understood. Thus we all recognize certain glacial, periglacial, or humid tropical landform types, even though processes such as the exact efficacy of deep glacial erosion, or long term rock-glacier formation and mechanics, or bornhardt generation may remain somewhat elusive. Furthermore, in the temperate latitudes where so many geomorphologists live and work, with the plethora of morphoclimatic process overprints, such as, for example, the Pleistocene glacial signatures impressed upon so much of the landscape of Europe and North America, it may surprise some that aspects of this now vanished glacial process still remain somewhat enigmatic.

Nevertheless, the fact that climate change has occurred so many times in the past is not in dispute, although the lability or amount of time that a given landform may take to come into equilibrium existence in a particular climate type may not be at all well understood. Thus a renewal of interest in the topic of climatic geomorphology seems entirely justified as we seek to better understand the many ways that climate forcings produce landforms. Nonetheless, one point that Professor Guti6rrez makes in this book that must always be kept in mind is expressed by the principle of convergence or equifinality, in which different processes produce the same landform so that oversimplified climatic explanations do not work. For example, granites and some other massive crystalline and sedimentary rocks weather and erode to produce tors in a variety of climatic regimes from tropical humid to periglacial. Long-term chemical weathering of certain minerals in these rocks, with later stripping of the weathered mantles, occurs in a variety of climate regimes. Similarly, frost shattering and gelifluction processes can also produce these bedrock tots. In the same equifinality fashion, horizontally bedded sedimentary and volcanic rocks can produce similar cliffed topography in various climates wherever the free faces are maintained by undercutting of the resistant rocks, even through dramatic climate changes. Excellent examples include the buttes and mesas of the deserts and pluvial basins of the southwestern USA, or the tepui mesas over which Angel Falls flows in the Amazonian rainforest of Venezuela. Similarly, bog-burst mass movement landforms can occur wherever rainfall and edaphic conditions allow saturated conditions to generate unstable peat bogs, be it tropical humid highlands, humid temperate maritime regions, or periglacial tundras. But in spite of such landform convergence, or the palimpsest landform

inheritance from past climatic regimes, understandings of climatic geomorphology still have much to offer those who utilize the appropriate concepts.

This book is structured into eight main sections that are set up first as an introduction to some of the history of geomorphology, then separate groupings of multiple chapters on glacial, periglacial, arid, aeolian, tropical, and climate-change geomorphology. The 25 different chapters in all of the sections discuss the dominant weathering, erosion, and deposition associated with the processes characteristic of each climate zone, along with the resulting erosional and depositional landforms. Strikingly, four chapters on applied aspects of glacial, periglacial, arid, and tropical landform processes and products provide an exceptionally important primer for many parts of the less developed world. This aspect will recommend the book to those in government offices or in the various development agencies world-wide who may need to better understand hazards or opportunities for assisting their citizenry to live more effectively in their particular climatic environments.

The dominant fluvial regimes of the temperate latitudes receive only limited attention in this book, which may somewhat reduce interest for those geomorphologists who specialize in such aspects in their regions. I suspect, however, that most geoscientists will still recognize the importance of the arid and tropical zones to so many people of the less developed world, and therefore will understand the reasons for the particular emphases in this book. In addition, the lack of a quantitative approach in the book, or the overall dearth of formulas may not meet the preferences of some, but still the many graphs and diagrams taken from the primary references do cover adequate quantitative materials.

Although the author of this book is well versed in the whole of climatic geomorphology, he has devoted about one third of the book to arid-zone topics, perhaps reflecting some of his main interests in interior, semi-arid Spain. Out of a total of 25 chapters, after the introductory chapter, 10 are on aeolian, arid zone, and applied arid topics. Next comes the glacial zone, with five chapters, and the periglacial and tropical zone sections with three chapters each. The last section on geomorphology and climate change also includes three chapters, which may add a measure of considerable interest to those younger geomorphologists who are going to live through what promise to be the most interesting climate changes to come in the 21st century. This book provides some mental preparation for recognizing and perhaps dealing with the most likely changes that can be expected.

The great majority of references in this book are in fact from the English-language literature, and thus these concepts originally had to be converted into Spanish for the initial volume. But because this book was then translated from the Spanish back into English by some ten different translators, some of our phraseology may be a little less artful than intended by the original authors of the primary references. If this is detected by anyone I must plead guilty myself to the difficulty presented in editing some of the literal translations back into the rather more idiomatic presentations that exactly reflect the original intentions, as well as being also quite accurate scientifically. We of the editorial staff did our best to convey the key ideas and information without error, but some few problems may have crept in inadvertently in this fashion anyway, inasmuch as we did not elect to rewrite the text from the original primary references. By and large the original text was also left fairly unmodified in the editorial process, with the exception of a few added observations and more up-to-date references that were felt to enhance the text.

The disconnect between the dominant studies of process geomorphology of the last half of the 20th century, or what has been referred to as timeless geomorphology, and an adequate exposition of time-bound landform evolution has become obvious to many geomor-phologists at the beginning of the 21 st century. This book, Climatic Geomorphology, is put forward as one approach to better understanding landform evolution from a climatic controlof process such that the time bound nature of the control is seen to exert both subtle and obvious process-directed changes to the landscape. An alternative and quantitatively robust approach to achieving this same result can be observed at many of the more advanced geoscientific meetings of the world today wherein the equations of climate-controlled process mechanics are run iteratively with computers to synthesize landscape evolution. Decades of new work in this vein are likely to be required to make adequate and realistic

progress with this new technology, but this robust methodology is already producing dramatic results. It is likely that this book can serve as one of the background sources of concepts and references that will enable better understanding of these process mechanics under certain climate forcings, and the inevitable fluctuations that must result from climate change. In this fashion we may eventually come to better understand the rich variety of climatically controlled landscapes that dominate planet Earth.

The publication of this book, Climatic Geomorphology, represents the first of the now rejuvenated series on Developments in Earth Surface Processes published by Elsevier. Geomorphology in the 21st century seems to be undergoing a renaissance of theory and methodologies as we recover from the paucity of robust theoretical underpinnings following the partial collapse and/or dramatic revisions of the Davisian-Penckian-Kingian paradigms in the middle of the prior century. After research excursions deep into the reductionistic thickets of process geomorphology, we now seem poised to move on smartly with the integration of short-term, timeless, landform process studies into long-term, time- bound, landform evolution. This book is offered as a rejuvenated first in a series of what is hoped will be an ever-increasing list of titles of new developments in geomorphology.

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