Lake outbursts
The catastrophic release of impounded water in smallish glacial lakes creates medium-scale geomorphic features. The Watrous spillway, Saskatchewan, Canada, rapidly incised during a short-lived outburst from glacial Lake Elstow Kehew and Teller 1994 . In its outlet area, the bed of Lake Elstow was composed of stagnant ice. The 40-km-long spillway cuts across a divide, and ends in the glacial Last Mountain Lake basin, where a coarse-grained fan was deposited. Large clasts are concentrated on the...
V
Reflection by polar S snow and ice cover Reflection by tropical convective clouds Figure 9.3 Conceptual diagrams of top planetary albedo and bottom land surface albedo versus surface temperature and evapotranspiration, respectively. Source Reprinted with kind permission of Springer Science and Business Media from A. Kleidon and K. Fraedrich 2004 Biotic entropy production and global atmosphere-biosphere interactions. In A. Kleidon and R. D. Lorenz eds Non-equilibrium Thermodynamics and the...
Diversity cycles
The diversity life has fluctuated through the Phanerozoic with the fossil record yielding up tantalizing suggestions of periodicity. Researchers claim to have teased out cycles of varying length using varied information, including diversity, first and last appearances, and extinction and origination rates. Early work on marine data hinted at a 30-million-year cycle Fischer 1984 that expresses itself in the global diversity of planktonic and nektonic taxa, including globigerinacean foraminifers...
The Gaia hypothesis
Life wields a potent influence on the composition of the atmosphere composition, producing a chemical disequilibrium, as seen in the high concentration of reactive atmospheric oxygen. Photosynthesis sustains this chemical disequilibrium by releasing oxygen and removing carbon dioxide from the air. It occurred to James Lovelock 1965 , an atmospheric chemist, that such a non-equilibrium atmospheric state would be a guide to the presence of life on other planets see also Hitchcock and Lovelock...
Plate tectonics
The idea of lithospheric plates Figure 2.2 emerged with the acceptance of continental drift. If the continents have drifted, as Alfred Lothar Wegener 1915 claimed, then large chunks of crust including continental cratons and deep ocean basins have travelled several thousand kilometres without having suffered any appreciable lateral distortion. Two features indicate this lack of distortion. First, is the excellent 'fit' of the opposing South American and African coastlines, which have taken 200...
Acknowledgements
I should like to thank the usual suspects who have made the completion of this book possible Nick Scarle for drawing the diagrams Andrew Mould for taking on board a 'research monograph' with limited sales potential Anja Scheffers for kindly letting me use her photographs and the University of Manchester for granting me a semester's research leave. As always, special thanks go to my wife, and to my two youngest children for letting me use my PC between sessions of Battle for Middle-Earth,...
Plume tectonics
The reassessment of the mantle plume hypothesis has become the most exciting current debate in Earth science Foulger 2005 . To appreciate the dynamics of the debate, it is useful to consider the mantle plume model before exploring the reasons for its possible demise and replacement with a plate model. Mantle plumes may start growing the core-mantle boundary. The mechanisms by which they form and grow are undecided. They may involve rising plumes of liquid metal and light elements pumping latent...
Debates and the geosphere
For many centuries, the bowels of the Earth were a matter of intense conjecture with little evidence against which to assess the worth of rival ideas. For some time after the Renaissance, most scholars accepted the system proposed by Empedocles and elaborated by Aristotle, which maintained that there were four elements - air, earth, fire, and water. They believed that the Earth was a solid, spherical body composed of assorted metals, rocks, and earth, within which were underground regions of...
Debates and the biosphere
Evolutionary theory began with Charles Darwin and Alfred Russel Wallace. The key arguments of their joint 1858 paper were, briefly all organisms produce more offspring than their environment can support abundant variations of most characters occur within species competition of limited resources creates a struggle for life or existence descent with heritable modification occurs and, in consequence, new species evolve Kutschera and Niklas 2004 . Neo-Darwinism began when August Weismann 1892...
The tempo of evolution
The fossil record yields up evidence of evolution. A big debate surrounds the pattern of evolution - is it slow and stately gradualism or does it proceed by rapid change followed by periods of stasis punctuated equilibrium . Gradualism versus punctuated equilibrium Othenio Abel 1929 and George Gaylord Simpson 1953 distinguished between phyletic change anagenesis and phylogenetic change speciational change or cladogenesis . Phyletic change occurs within a single lineage, whereas phylogenetic...