The Physical Geography of Africa

The Physical Geography of Africa

The Physical Geography of Africa

The Physical Geography of Africa

Synopsis

An international team of distinguished scholars have each contributed a chapter to produce an advanced, full length, physical geography of Africa. The first part provides an overview of both pan-Africa patterns in the physical environment and those attributes of African physical geography that are distinctive by considering the development of the main features through time. The authors also provide a synoptic review of Francophone and Anglophone literature on the subject, discuss the present state of knowledge, and set out the work and methods that have created it. This part is followed by a group of chapters that integrate such topics as geomorphology, biogeography, environmental change and hydrology within each of the major biomes - forest, savannah, desert, coast, wetland, mountain, Mediterranean and Rift Valley - found in the African continent. Finally there is a section in which various authors look at topical issues concerned with the impact of human activity on the environment. Conservation and development are considered in the light of issues such as soil erosion, desertification, and biodiversity and biodepletion. The authors have produced this integrated physical geography in honour of A.T. Grove as a durable reference work which gives a new perspective on the continent of Africa.

Excerpt

In this chapter I aim to provide a general background to some key aspects of the tectonic, geological, and landscape development of Africa, the framework which provides much of the setting for the physical geography of the continent. Limited to a necessarily brief review of an enormously diverse and intensively studied range of topics, my focus is on some of the concepts and data that have recently emerged and which illuminate our understanding of the tectonic and macro-scale morphological evolution of the African continent; relevant coverage of earlier material is to be found in two previous reviews (Summerfield, 1985a, b). Such a spotlight on new observations and ideas is particularly apposite because the continent of Africa has become something of a test-bed for tectonic and geomorphic models over the past decade or so with the development of ideas on continental breakup and the role of mantle plumes (White and McKenzie, 1989), and the beginnings of a better understanding of the denudational history of the continent through the application of novel analytical techniques, such as fission-track analysis (Brown et al., 1990, 1994; Omar et al., 1989), and the availability of digital topographic data and increasingly detailed information on offshore stratigraphy (Emery and Uchupi, 1984; Rust and Summerfield, 1990).

I begin by examining the macro-scale morphology of Africa and then briefly describe the structural development of the continent. I go on to assess the stratigraphic record and changing palaeogeography of Africa, in particular with respect to the information these can provide about its Mesozoic and Cenozoic topographic history, and then discuss the thermal and tectonic mechanisms which have been invoked to explain the evolution of the present gross morphology. The chapter is concluded with an evaluation of the significance of these tectonic models and our increased knowledge of the denudational history of Africa for previous ideas about the post-Gondwana evolution of the African landscape.

First-order Morphology

The recent availability of digital elevation datasets means that it is now possible to assess with relative ease the statistical properties of the morphology of the African continent. Given that it lacks a significant area of Mesozoic or Cenozoic orogens with their associated zones of crustal thickening, the mean elevation of Africa is relatively high compared with the other major continental blocks. Its mean elevation with respect to sea-level is 651 m on the basis of one-degree digital elevation values (Cogley, 1985), but higher resolution 10-minute digital data produces a latitudinally weighted mean of 641 m. Of particular interest is the way elevation is distributed with respect to area in the African continent. This is clearly illustrated through a comparison of the hypsometry of Africa and South America which reveals . . .

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