The first step in preparing Geomorphology from Space was to select its contents and to design its format. The core of the book is a gallery of space imagery consisting of 237 Plates,3 each treating some geographic region where a particular landform theme is exemplified. A Plate usually consists of a two-page spread with the image on the right side, a commentary (an extended caption) on the left, and ancillary (supporting) photographs, index (locator) maps, and sometimes a geologic map at the bottom of both pages. A few four- or six-page spreads are allotted to mosaics or oversized images, or to topics requiring extended text and more photographs. Many ancillary photographs were trimmed to allow a maximum of four per Plate where appropriate; if used as ancillaries, the skewed sides of Landsat images were squared off (less than 10 percent of the rhombic-shaped original image is lost) to maintain a balance of shapes across the photo sequence.

In one sense, this gallery stamps Geomorphology from Space as mainly an atlas-like collection of images, except that the emphasis in the commentaries is centered on the scientific information content of the primary image. The arrangement of the gallery is by geomorphic theme: (1) Tectonic (Structural), (2) Volcanic, (3) Fluvial, (4) Delta, (5) Coastal, (6) Karst and Lakes, (7) Eolian, (8) Glacial, and (9) Planetary Landforms. This last topic is in keeping with the current awareness of the importance of (comparative) planetary geomorphology to the NASA space exploration program in general and with the growing realization that understanding of formative processes of surface features on other planets has obvious feedback effects on recognizing many terrestrial counterparts. The number of Plates allotted to each gallery chapter varies from 15 to 27 for all but one chapter. The Tectonic chapter is deliberately made longer for two reasons: (1) the natural diversity of tectonic landforms warrants a larger number of Plates to provide adequate coverage of the variability, and (2) the realization as writing proceeded that the commentaries offer a powerful synoptic overview and summary of the general geology of the entire globe, especially of the major shields and orogenic belts.

The sequence of Plates within each chapter was determined by the author(s) of that section. Two choices were available -arrangement either by geographical distribution (beginning in North America and proceeding through South America, Europe, Africa, and Asia) or according to a thematic classification (e.g., types of deltas) established by the author. That classification, if devised, appears in an introductory section that opens each gallery chapter. This section also reviews the current state of knowledge about the landforms in the chapter theme, aspects of their origin and development, and their appearance at regional scales.

The bulk of the images in this book are those taken by the Multispectral Scanner (MSS) on Landsats 1, 2, and 3, the Return Beam Vidicon (RBV) on Landsat 3, and the Thematic Mapper (TM) on Landsats 4 and 5. (See Appendix A for a summary of sensor systems and a brief review of remote sensing concepts and information extraction procedures relevant to the appreciation of the multispectral images appearing in this book.) In general, Landsat images predominate in this book because they have proved to be the most informative, often the most photogenic, and the most readily obtainable. A complete collection of Landsat 1 through 3 images collected through 1978, many Landsat 4 and 5 images, and HCMM and SIR-A images were accessible for inspection at GSFC. The remaining space images include early photographs from Gemini and Apollo and later ones taken from the Shuttle by astronauts using the Large Format Camera or hand-held cameras, as well as radar images obtained by the Seasat SAR and SIR-A and -B (on the Shuttle) and thermal and visible images acquired by HCMM. As a policy, when a non-Landsat scene was available, the final choice of it over Landsat as the primary Plate image was based on its visual superiority, its coverage of an area not matched by Landsat (as in tropical cloud-covered regions), and the new information content and/or different perspective of the scene.

Most of the more than 400 gallery images initially considered for the book were chosen by the editors. The bulk of these were originally processed from film negatives obtained from the EROS Data Center or from the Landsat Browse Facility at GSFC. The candidate images were then pared down to the final 237 by the author(s) of each gallery chapter.

Nearly all Plates are accompanied by three to four ancillary photographs. In many instances, either Landsat or non-Landsat space images were used as ancillaries. Other candidates for ancillaries were oblique and vertical aerial photographs, ground panoramic views, and a few closeup pictures. Most ancillary photographs depict a location somewhere in the image area and show pertinent geomorphic, structural, or other geologic features discussed in the commentary. When ancillaries located within the scene were not available, the editors or authors substituted either representative photographs from outside the image or appropriate maps. Nearly all Plates are accompanied by an index map that identifies major geographic and geologic features, either by name or by a letter, called out in the commentary. All spellings of geographic terms and locations used on these maps and in the text are taken from the 1982 edition of the National Geographic Society Atlas of the World. Landsat MSS images are printed at approximately 1:1000000 scale (18.3 cm or 7.2 inches) but may deviate slightly where layout spacing would lead to crowding.

A word about the illustration numbering system adopted for this book follows. The main image for each Plate is identified in the text by the first letter of the landform type to which a chapter is dedicated and a sequential number. For example, the first three Plate images in the Fluvial Landforms chapter are Plates F-1, F-2, and F-3. The ancillary illustrations are numbered as shown in this example for three such figures in Plate F-2, namely Figures F-2.1, F-2.2, and F-2.3. However, the actual illustrations (usually photographs) are tied to their figure callouts by a single number for each (e.g., 1, 2, and 3, located in the lower left corner of the figure itself). There are no accompanying captions; identification and any description are incorporated directly into the full text for the Plate. Photographs, images, and line drawings in the nongallery chapters and in the introductions to the landform theme chapters (gallery) themselves are designated by the chapter number and the number sequence for the figures. For instance, the fourth figure in Chapter 11 (Geomorphic Mapping) is given as Figure 11-4; captions accompany this category of figures. This diverse numbering system allows for easy recognition of what the figure should highlight whenever cross-referenced; thus, a reader encountering a reference to Figure V-4.2 in a caption for an Eolian chapter Plate would quickly surmise it to be a volcanic ancillary for the fourth Plate in the Volcanic Landforms chapter. The normal arrangement for an ancillary illustration sequence is the customary 1, 2, 3, 4, left to right across the two facing pages, with the index map on the far right; however, in a few instances, odd illustration sizes or other unusual circumstances prompt variations in this sequence.

The orientation of most space images can be determined in two ways: (1) for Plate images, latitude/longitude tick marks appear along the top and right margins of the accompanying index map, and (2) for ancillary Landsat images, north typically points topwise, slanted left along a line making about an 110 angle with the cropped left/right margin of the illustration. In a few cases, north arrows are imposed on images other than Landsat to specify the orientation. Distance scales are drawn on index maps for images other than those of normal (full) Landsat, HCMM, Seasat, SAR, and SIR-A scenes. For these four observation systems, equivalent dimensions are fixed as follows: Base of Landsat MSS or TM = 185 km across; base of Landsat RBV = 92 km; base of HCMM = 716 km; width of Seasat SAR = 100 km; and width of SIR-A = 50 km.

In preparing this book, acquisition of satisfactory ancillaries proved to be the most formidable problem. Many photographs came from an author's personal collection or from his/her contacts with colleagues having comparable interests. Each author was responsible for finding most of the needed ancillaries; this worked well for the chapters on Volcanic, Delta, and Glacial Landforms, but shortfalls occurred for other chapters, especially that for Tectonic Landforms. A supporting search by the editors to fill these gaps concentrated on sending more than 150 letters of request to organizations and individuals in 39 countries (in all, scenes from 58 countries appear in this book) asking for any appropriate pictures that tied into the images. The percentage of success in this approach was a disappointing 30 percent (approximated). Three factors account for this low return: (1) most of those asked to help did not fully appreciate the value of their contribution or simply did not have the time to go through image files to match their coverage with that of the space images; (2) relatively few panoramic ground or aerial oblique views (such as those taken by John A. Shelton, who is noted for this type of photograph and who is a contributor to this book), are available in the first place; and (3) many countries have strict policies against release of official photos (such as those obtainable from geologic surveys) to other nations.

Nevertheless, many superb contributions were received, as gratefully acknowledged in the credits (including copyright statements) listed in Appendix B. However, the photographs were often submitted as 35-mm color slides that had to be converted to black and white prints that lose detail or sharpness and often internal contrast in the process. Other photographs were those used in the contributors' own publications or books. Many pictures were purchased from the U.S. Geological Survey and the Canadian Geological Survey photolibraries. Still, all in all, the initial hopes for a plethora of "outstanding" ancillaries were not fully realized.

A word about color: Mission to Earth owes much of its success to its nearly 400 color plates. Today, with publication costs more of a factor, the number allotted to Geomorphology from Space is much reduced. The images finally picked for this special treatment are either mosaics or are simply more "beautiful" in color than in black and white. Generally, landforms are characterized more by their shape than by color. Thus, a black and white version communicates almost the same essential geomorphic information as a color one.

The commentaries for the Plates in each gallery chapter were written by the chapter author unless otherwise stated. For the coauthored Tectonic Landforms chapter, the principal writer of a particular commentary is identified at the end of its text. A special situation, involving students at the University of Maryland who contributed background information for a given scene in the Tectonic Landforms chapter, is explained in its introduction; the person who secured that information is listed in Appendix B. A few guest authors were asked to write commentaries for specific Plates; these individuals are named at the end of the commentary text following the initials GCW (for Guest Caption Writer); then affiliations are given in Appendix B. Literature references used in preparing individual commentaries are cited by author names and year within and/or at the end of the text for each Plate. Full references appear at the end of each chapter.

Besides the gallery, several other chapters complete this book. The opening one is an overview and evaluation of the present status of the regional or synoptic approach to the study of landforms, prepared by Victor R. Baker, a geomorphologist at the University of Arizona. This chapter, which precedes the gallery, reviews the history of "scale" or level of observable detail in the development of geomorphic concepts, defines the newly named subfield of mega-geomorphology and weighs its advantages, and explores the role of space imagery as a viable data source for characterizing and analyzing landforms from a global perspective. The first chapter after the gallery, written by Robert Hayden of George Mason University, examines the evolution of geomorphic unit mapping and demonstrates the applicability of space imagery in producing this type of map.

The closing chapter reviews a conference that was a direct outgrowth of the commitment to this book. Because the book was well under way, Mark Settle, then program manager for geologic studies in the Earth Observations Program within NASA, commissioned the senior editor to organize a Workshop cosponsored by NASA and the International Union of the Geological Sciences on "Global Mega-geomorphology" that would delve into many of the same objectives already outlined in this book. Thirty-two individuals, including all contributing authors of Geomorphology from Space and some key workers in landform studies from academia, industry, and the U.S. Geological Survey, met near Tucson, Arizona, on January 13-17, 1985. Some of the principal ideas, conclusions, and recommendations reached at this workshop are summarized in the last chapter by Robert Hayden of George Mason University, Robert W. Blair, Jr., Fort Lewis College, and James Garvin and Nicholas M. Short, Goddard Space Flight Center.

Even as typesetting of this book was nearly complete, a major space event opened up another dimension for the practical use of synoptic imagery in regional geomorphic analysis. The successful launch of the French Système Probatoire pour l'Observation de la Terre (SPOT) spacecraft for the first time will allow worldwide acquisition of high-resolution multispectral stereographic images, so that the Earth's landscapes can now be viewed in relief. An Epilogue after the final chapter describes the SPOT system and offers striking examples of this new stereo capability.  


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