scholarly journals The fluvial history of Mars

2012 ◽  
Vol 370 (1966) ◽  
pp. 2193-2215 ◽  
Author(s):  
Michael H. Carr
Keyword(s):  
Climatic Conditions ◽  
River Channels ◽  
Erosion And Deposition ◽  
Running Water ◽  
The Earth ◽  
Outflow Channels ◽  
History Of ◽  
Valley Networks ◽  
River Valleys ◽  
Steep Slopes

River channels and valleys have been observed on several planetary bodies in addition to the Earth. Long sinuous valleys on Venus, our Moon and Jupiter's moon Io are clearly formed by lava, and branching valleys on Saturn's moon Titan may be forming today by rivers of methane. But by far the most dissected body in our Solar System apart from the Earth is Mars. Branching valleys that in plan resemble terrestrial river valleys are common throughout the most ancient landscapes preserved on the planet. Accompanying the valleys are the remains of other indicators of erosion and deposition, such as deltas, alluvial fans and lake beds. There is little reason to doubt that water was the erosive agent and that early in Mars' history, climatic conditions were very different from the present cold conditions and such that, at least episodically, water could flow across the surface. In addition to the branching valley networks, there are large flood features, termed outflow channels. These are similar to, but dwarf, the largest terrestrial flood channels. The consensus is that these channels were also cut by water although there are other possibilities. The outflow channels mostly postdate the valley networks, although most are still very ancient. They appear to have formed at a time when surface conditions were similar to those that prevail today. There is evidence that glacial activity has modified some of the water-worn valleys, particularly in the 30–50° latitude belts, and ice may also be implicated in the formation of geologically recent, seemingly water-worn gullies on steep slopes. Mars also has had a long volcanic history, and long, sinuous lava channels similar to those on the Moon and Venus are common on and around the large volcanoes. These will not, however, be discussed further; the emphasis here is on the effects of running water on the evolution of the surface.

Effects of Continents and Supercontinents on Climate

2004 ◽  
Author(s):  
John J. W. Rogers ◽  
M. Santosh
Keyword(s):  
Global Climate ◽  
Climatic Conditions ◽  
Polar Regions ◽  
The North ◽  
Rock Types ◽  
Control Climate ◽  
The Earth ◽  
History Of ◽  
Earth’S Climate ◽  
Geologic Record

Continents affect the earth’s climate because they modify global wind patterns, control the paths of ocean currents, and absorb less heat than seawater. Throughout earth history the constant movement of continents and the episodic assembly of supercontinents has influenced both global climate and the climates of individual continents. In this chapter we discuss both present climate and the history of climate as far back in the geologic record as we can draw inferences. We concentrate on longterm changes that are affected by continental movements and omit discussion of processes with periodicities less than about 20,000 years. We refer readers to Clark et al. (1999) and Cronin (1999) if they are interested in such short-term processes as El Nino, periodic variations in solar irradiance, and Heinrich events. The chapter is divided into three sections. The first section describes the processes that control climate on the earth and includes a discussion of possible causes of glaciation that occurred over much of the earth at more than one time in the past. The second section investigates the types of evidence that geologists use to infer past climates. They include specific rock types that can form only under restricted climatic conditions, varieties of individual fossils, diversity of fossil populations, and information that the 18O/16O isotopic system can provide about temperatures of formation of ancient sediments. The third section recounts the history of the earth’s climate and relates changes to the growth and movement of continents. This history takes us from the Archean, when climates are virtually unknown, through various stages in the evolution of organic life, and ultimately to the causes of the present glaciation in both the north and the south polar regions. The earth’s climate is controlled both by processes that would operate even if continents did not exist and also by the positions and topographies of continents. We begin with the general controls, then discuss the specific effects of continents, and close with a brief discussion of processes that cause glaciation. The general climate of the earth is determined by the variation in the amount of sunshine received at different latitudes, by the earth’s rotation, and by the amount of arriving solar energy that is retained in the atmosphere.

George Hoggart Toulmin: politics and geology

1978 ◽  
Vol 8 (4) ◽  
pp. 481-481
Author(s):  
ROY PORTER
Keyword(s):  
French Revolution ◽  
Social Order ◽  
Lower Class ◽  
Great Distance ◽  
The Earth ◽  
Christian View ◽  
The Social ◽  
French Enlightenment ◽  
Political Conservatism ◽  
History Of

The physician George Hoggart Toulmin (1754–1817) propounded his theory of the Earth in a number of works beginning with The antiquity and duration of the world (1780) and ending with his The eternity of the universe (1789). It bore many resemblances to James Hutton's "Theory of the Earth" (1788) in stressing the uniformity of Nature, the gradual destruction and recreation of the continents and the unfathomable age of the Earth. In Toulmin's view, the progress of the proper theory of the Earth and of political advancement were inseparable from each other. For he analysed the commonly accepted geological ideas of his day (which postulated that the Earth had been created at no great distance of time by God; that God had intervened in Earth history on occasions like the Deluge to punish man; and that all Nature had been fabricated by God to serve man) and argued they were symptomatic of a society trapped in ignorance and superstition, and held down by priestcraft and political tyranny. In this respect he shared the outlook of the more radical figures of the French Enlightenment such as Helvétius and the Baron d'Holbach. He believed that the advance of freedom and knowledge would bring about improved understanding of the history and nature of the Earth, as a consequence of which Man would better understand the terms of his own existence, and learn to live in peace, harmony and civilization. Yet Toulmin's hopes were tempered by his naturalistic view of the history of the Earth and of Man. For Time destroyed everything — continents and civilizations. The fundamental law of things was cyclicality not progress. This latent political conservatism and pessimism became explicit in Toulmin's volume of verse, Illustration of affection, published posthumously in 1819. In those poems he signalled his disapproval of the French Revolution and of Napoleonic imperialism. He now argued that all was for the best in the social order, and he abandoned his own earlier atheistic religious radicalism, now subscribing to a more Christian view of God. Toulmin's earlier geological views had run into considerable opposition from orthodox religious elements. They were largely ignored by the geological community in late eighteenth and early nineteenth century Britain, but were revived and reprinted by lower class radicals such as Richard Carlile. This paper is to be published in the American journal, The Journal for the History of Ideas in 1978 (in press).

Computers in Geology - 25 Years of Progress

1994 ◽  
Keyword(s):  
Computer Modeling ◽  
Quantitative Methods ◽  
State Of The Art ◽  
International Association ◽  
Mathematical Geology ◽  
25Th Anniversary ◽  
The Earth ◽  
Wide Range ◽  
History Of ◽  
Mapping Techniques

This volume vividly demonstrates the importance and increasing breadth of quantitative methods in the earth sciences. With contributions from an international cast of leading practitioners, chapters cover a wide range of state-of-the-art methods and applications, including computer modeling and mapping techniques. Many chapters also contain reviews and extensive bibliographies which serve to make this an invaluable introduction to the entire field. In addition to its detailed presentations, the book includes chapters on the history of geomathematics and on R.G.V. Eigen, the "father" of mathematical geology. Written to commemorate the 25th anniversary of the International Association for Mathematical Geology, the book will be sought after by both practitioners and researchers in all branches of geology.

The Thermal History of the Earth

Nature ◽  
1956 ◽  
Vol 177 (4500) ◽  
pp. 155-157 ◽  
Author(s):  
J. A. JACOBS ◽  
D. W. ALLAN
Keyword(s):  
Thermal History ◽  
The Earth ◽  
History Of

Early accretional history of the Earth and the Moon-forming event

Lithos ◽  
1993 ◽  
Vol 30 (3-4) ◽  
pp. 207-221 ◽  
Author(s):  
Stuart Ross Taylor
Keyword(s):  
The Moon ◽  
The Earth ◽  
History Of

scholarly journals In-Situ Cosmogenic 14C: Production and Examples of its Unique Applications in Studies of Terrestrial and Extraterrestrial Processes

Radiocarbon ◽  
2001 ◽  
Vol 43 (2B) ◽  
pp. 731-742 ◽  
Author(s):  
D Lal ◽  
A J T Jull
Keyword(s):  
Half Life ◽  
Earth Science ◽  
Chemical Properties ◽  
Radioactive Isotopes ◽  
Earth’S Atmosphere ◽  
The Earth ◽  
Wide Range ◽  
History Of ◽  
Earth's Atmosphere

Nuclear interactions of cosmic rays produce a number of stable and radioactive isotopes on the earth (Lai and Peters 1967). Two of these, 14C and 10Be, find applications as tracers in a wide variety of earth science problems by virtue of their special combination of attributes: 1) their source functions, 2) their half-lives, and 3) their chemical properties. The radioisotope, 14C (half-life = 5730 yr) produced in the earth's atmosphere was the first to be discovered (Anderson et al. 1947; Libby 1952). The next longer-lived isotope, also produced in the earth's atmosphere, 10Be (half-life = 1.5 myr) was discovered independently by two groups within a decade (Arnold 1956; Goel et al. 1957; Lal 1991a). Both the isotopes are produced efficiently in the earth's atmosphere, and also in solids on the earth's surface. Independently and jointly they serve as useful tracers for characterizing the evolutionary history of a wide range of materials and artifacts. Here, we specifically focus on the production of 14C in terrestrial solids, designated as in-situ-produced 14C (to differentiate it from atmospheric 14C, initially produced in the atmosphere). We also illustrate the application to several earth science problems. This is a relatively new area of investigations, using 14C as a tracer, which was made possible by the development of accelerator mass spectrometry (AMS). The availability of the in-situ 14C variety has enormously enhanced the overall scope of 14C as a tracer (singly or together with in-situ-produced 10Be), which eminently qualifies it as a unique tracer for studying earth sciences.

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