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Meteorite Craters
183
which gives separate names to different portions of a spectrum of variations will inevitably run into problems of how to classify rocks on the borderline between two regions of the spectrum. F. Chayes concentrates on the problem of improving the consistency with which rocks are named (in any classification). The review could, however, have included much other material on igneous rock classifications, such as attempts to classify rocks by phenocryst assemblage, by associations, and by thermodynamic parameters. Overall, then, this is a volume of variable qua!ity of presentation and it suffers from those faults which one must expect in such an enterprise. Outstanding contributions have been provided by E. Roedder on liquid immiscibility (Chapter 2), N. Irvine on rocks formed by crystal sorting (Chapter 9), and C.W. Burnham on the role of volatiles (Chapter 16) in particular. My criticisms are concerned much more with the quantity which is not included than with the quality of what is included. In several chapters these deficiencies are serious enough to justify the criticism that this book fails in these areas to meet its own targets. Where it is good, however, it is excellent, and above all excellent value in paperback for all students of igneous petrology,
Information based on the more than 55000 pietures taken of the surface, the detailed gravity tracking data and the multitude of JR observations that defined the water—ice composition of the north polar cap is not adequately covered. In summary, the book is interesting and valuable as a preliminary report that presents a limited part of the data obtained for Mars in the 1970s. Wells has done a thorough job of describing the ground-based and Mariner 9 observations of Mars. He has devoted much attention to the chemical composition of the atmosphere, its variability and determination techniques. He also devotes much effort and space to the Mariner 9 mapping of surface features and lineaments and gives a detailed description of the gravity field and possible continental drift on Mars. His discussion of possible mantle convection gives adequate attention to Runcorn’s contributions. This is still an area of active controversy and the newer data on Mars and Venus will keep this discussion alive. The discussions of the meteorology and geology are incomplete. The discussions of blue hazes and clearings and the “wave of darkening” are very controversial and possibly non-existent. The discussions of topography are superceded by the new series of maps based on Viking data that are being
Mi. O’HARA (Aberystwyth)
published currently. His discussion of Mie scattering theory is effective, as are the discussions of the interaction of the atmosphere and surface. The diagrams and photographs are clear and informative. The cost of the book is high but it is a valuable document to complement the more recent cornpendia of papers and T. Mutch’s book on the Geology of Mars.
Review of Geophysics of Mars. R.A. Wells. Developments in Solar System and Space Science, Vol. 4, Elsevier, Amsterdam, 1979, xxii + 678 pp., Dfl. 180.00, U.S. $ 87.75, ISBN 0-44441802-4. Wells has worked hard to summarize the data on Mars in a coherent fashion. The main difficulty with his work is that Mars research has moved so rapidly that his account is, of necessity, very dated and therefore incomplete. This compendium is really based on the Mariner 9 data with some additions based on Viking data added later. However, a multitude of Viking science reports, the data from the 1st and 2nd Mars Colloquia and many other papers on the Viking extended mission have now been written. The Viking Orbiter I spacecraft was not turned off until August 8, 1980.
H. MASURSKY (flagstaff, AZ)
Meteorite Craters. G.J.H. McCall (Editor). Benchmark Papers in Geology, Vol. 36, Dowden, Hutchinson & Ross, Stroudsburg, PA, xiii + 364 pp., U.S. $ 36.50, U.K. £23.70, ISBN 0-12-787026-1. Spacecraft exploration has shown that impact cratering has been an important landforming pro-
184
cess on the Moon, terrestrial planets and the Galilean satellites. Interpretations of the history of each of these planetary bodies suggest that in the early history of the Solar System, prior to about 4 X l0~years ago, impact cratering dominated the geology of solid planets and their satellites, and it now seems unlikely that the Earth would have avoided impact destruction of its land surfaces. However, the terrestrial stratigraphic record only goes back to about 3.8 X l0~years and we may at present only speculate about this phase of the Earth’s history by using other planetary bodies for a comparison. Nevertheless, impact craters have been found throughout the whole history of the planetary bodies since that time, and wellpreserved impact craters are present on most planetary surfaces. Geologists were slow to recognise impact features on Earth, endeavouring to explain all craters in terms of the better known process of volcanism. This reluctance by geologists to accept impact probably results from the pervasive influence of umformitananism that had so successfully advanced geological understanding; impactcratering, a rarely observed phenomenon, smacked too much of catastrophism for the liking of many geologists, Recognition of the impact origin of lunar craters provided the necessary impetus to make geologists examine possible impact structures on Earth in more detail. A turning point in the history of geological understanding is marked by the classic paper by E.M. Shoemaker on Meteor Crater (reproduced in this book). In this paper, for the first time, Shoemaker examines the structure of the crater and compares it to artificial nuclear and high energy explosion craters where the conditions of formation are known and are in some ways similar to impact. Since that time, our knowledge of impact processes has advanced considerably and we are able to interpret the geology of craters more confidently in terms of the physical processes that formed them. It is the emphasis on understanding process since the Shoemaker paper that has dominated the study of meteorite craters since about 1960. However, little of this aspect of the science has been included in the book under review here. The papers chosen to illustrate the advancement of this sci-
ence are arranged in a classical style in terms of their morphology which in turn is related to structural form, degree of degradation and whether they have been “proved” as meteorite craters. By taking this approach, the editor has omitted papers of major importance that describe the physics of impact, concentrating more on the purely descriptive side of the subject. The pioneering work of Donald Gault, who used high speed photography of impact craters being formed by the Light Gas Gun at NASA Ames Research Center, is well known to all those working on meteorite craters; and yet his classic paper with W.L.Quaide and V.R. Overbeck published in 1968 is not included in this compendium. Sadly, the works of other authors, such as R.B. Baldwin, D.J. Roddy, M. Dence and B. French, who have placed emphasis on physical process, are also omitted from the list of authors represented. In any “Benchmark” book the choice of papers clearly represents the interests of the editor. In this book, most of the papers reproduced are important reading, but by concentrating on the more descriptive papers, the editor has missed out on the important steps taken towards understanding process during the l960s and 70s. J.E GUEST (London)
Seismic Migration. Imaging of Acoustic Energy by Wave Field Extrapolation. A.J. Berkhout. De-
velopments in Solid Earth Geophysics 12, Elsevier, Amsterdam, 1980, xii + 340 pp., Dfl. 120.00, U.S. $ 58.50, ISBN 0-444-41904-7. In seismic reflection surveying, a stacked seismic section consists of a series of seismograms, each of which represents an approximation to the reflection coefficient series which would be observed by a coincident source and receiver at the Earth’s surface. Successive seismograms come from equally spaced positions of the source and receiver along the seismic line. When a seismic profile is shot over dipping strata, the reflected arrivals on the seismograms will generally not have come from points vertically beneath the position of source and receiver. Migration is the process of repositioning each seismic arrival on the section to the
which gives separate names to different portions of a spectrum of variations will inevitably run into problems of how to classify rocks on the borderline between two regions of the spectrum. F. Chayes concentrates on the problem of improving the consistency with which rocks are named (in any classification). The review could, however, have included much other material on igneous rock classifications, such as attempts to classify rocks by phenocryst assemblage, by associations, and by thermodynamic parameters. Overall, then, this is a volume of variable qua!ity of presentation and it suffers from those faults which one must expect in such an enterprise. Outstanding contributions have been provided by E. Roedder on liquid immiscibility (Chapter 2), N. Irvine on rocks formed by crystal sorting (Chapter 9), and C.W. Burnham on the role of volatiles (Chapter 16) in particular. My criticisms are concerned much more with the quantity which is not included than with the quality of what is included. In several chapters these deficiencies are serious enough to justify the criticism that this book fails in these areas to meet its own targets. Where it is good, however, it is excellent, and above all excellent value in paperback for all students of igneous petrology,
Information based on the more than 55000 pietures taken of the surface, the detailed gravity tracking data and the multitude of JR observations that defined the water—ice composition of the north polar cap is not adequately covered. In summary, the book is interesting and valuable as a preliminary report that presents a limited part of the data obtained for Mars in the 1970s. Wells has done a thorough job of describing the ground-based and Mariner 9 observations of Mars. He has devoted much attention to the chemical composition of the atmosphere, its variability and determination techniques. He also devotes much effort and space to the Mariner 9 mapping of surface features and lineaments and gives a detailed description of the gravity field and possible continental drift on Mars. His discussion of possible mantle convection gives adequate attention to Runcorn’s contributions. This is still an area of active controversy and the newer data on Mars and Venus will keep this discussion alive. The discussions of the meteorology and geology are incomplete. The discussions of blue hazes and clearings and the “wave of darkening” are very controversial and possibly non-existent. The discussions of topography are superceded by the new series of maps based on Viking data that are being
Mi. O’HARA (Aberystwyth)
published currently. His discussion of Mie scattering theory is effective, as are the discussions of the interaction of the atmosphere and surface. The diagrams and photographs are clear and informative. The cost of the book is high but it is a valuable document to complement the more recent cornpendia of papers and T. Mutch’s book on the Geology of Mars.
Review of Geophysics of Mars. R.A. Wells. Developments in Solar System and Space Science, Vol. 4, Elsevier, Amsterdam, 1979, xxii + 678 pp., Dfl. 180.00, U.S. $ 87.75, ISBN 0-44441802-4. Wells has worked hard to summarize the data on Mars in a coherent fashion. The main difficulty with his work is that Mars research has moved so rapidly that his account is, of necessity, very dated and therefore incomplete. This compendium is really based on the Mariner 9 data with some additions based on Viking data added later. However, a multitude of Viking science reports, the data from the 1st and 2nd Mars Colloquia and many other papers on the Viking extended mission have now been written. The Viking Orbiter I spacecraft was not turned off until August 8, 1980.
H. MASURSKY (flagstaff, AZ)
Meteorite Craters. G.J.H. McCall (Editor). Benchmark Papers in Geology, Vol. 36, Dowden, Hutchinson & Ross, Stroudsburg, PA, xiii + 364 pp., U.S. $ 36.50, U.K. £23.70, ISBN 0-12-787026-1. Spacecraft exploration has shown that impact cratering has been an important landforming pro-
184
cess on the Moon, terrestrial planets and the Galilean satellites. Interpretations of the history of each of these planetary bodies suggest that in the early history of the Solar System, prior to about 4 X l0~years ago, impact cratering dominated the geology of solid planets and their satellites, and it now seems unlikely that the Earth would have avoided impact destruction of its land surfaces. However, the terrestrial stratigraphic record only goes back to about 3.8 X l0~years and we may at present only speculate about this phase of the Earth’s history by using other planetary bodies for a comparison. Nevertheless, impact craters have been found throughout the whole history of the planetary bodies since that time, and wellpreserved impact craters are present on most planetary surfaces. Geologists were slow to recognise impact features on Earth, endeavouring to explain all craters in terms of the better known process of volcanism. This reluctance by geologists to accept impact probably results from the pervasive influence of umformitananism that had so successfully advanced geological understanding; impactcratering, a rarely observed phenomenon, smacked too much of catastrophism for the liking of many geologists, Recognition of the impact origin of lunar craters provided the necessary impetus to make geologists examine possible impact structures on Earth in more detail. A turning point in the history of geological understanding is marked by the classic paper by E.M. Shoemaker on Meteor Crater (reproduced in this book). In this paper, for the first time, Shoemaker examines the structure of the crater and compares it to artificial nuclear and high energy explosion craters where the conditions of formation are known and are in some ways similar to impact. Since that time, our knowledge of impact processes has advanced considerably and we are able to interpret the geology of craters more confidently in terms of the physical processes that formed them. It is the emphasis on understanding process since the Shoemaker paper that has dominated the study of meteorite craters since about 1960. However, little of this aspect of the science has been included in the book under review here. The papers chosen to illustrate the advancement of this sci-
ence are arranged in a classical style in terms of their morphology which in turn is related to structural form, degree of degradation and whether they have been “proved” as meteorite craters. By taking this approach, the editor has omitted papers of major importance that describe the physics of impact, concentrating more on the purely descriptive side of the subject. The pioneering work of Donald Gault, who used high speed photography of impact craters being formed by the Light Gas Gun at NASA Ames Research Center, is well known to all those working on meteorite craters; and yet his classic paper with W.L.Quaide and V.R. Overbeck published in 1968 is not included in this compendium. Sadly, the works of other authors, such as R.B. Baldwin, D.J. Roddy, M. Dence and B. French, who have placed emphasis on physical process, are also omitted from the list of authors represented. In any “Benchmark” book the choice of papers clearly represents the interests of the editor. In this book, most of the papers reproduced are important reading, but by concentrating on the more descriptive papers, the editor has missed out on the important steps taken towards understanding process during the l960s and 70s. J.E GUEST (London)
Seismic Migration. Imaging of Acoustic Energy by Wave Field Extrapolation. A.J. Berkhout. De-
velopments in Solid Earth Geophysics 12, Elsevier, Amsterdam, 1980, xii + 340 pp., Dfl. 120.00, U.S. $ 58.50, ISBN 0-444-41904-7. In seismic reflection surveying, a stacked seismic section consists of a series of seismograms, each of which represents an approximation to the reflection coefficient series which would be observed by a coincident source and receiver at the Earth’s surface. Successive seismograms come from equally spaced positions of the source and receiver along the seismic line. When a seismic profile is shot over dipping strata, the reflected arrivals on the seismograms will generally not have come from points vertically beneath the position of source and receiver. Migration is the process of repositioning each seismic arrival on the section to the