Environmental Engineering Reference
In-Depth Information
KEY POINTS
1
Earth acquired its own heat engine and a particular set of planetary raw materials,
determined by its position in the solar system, at its formation. The continuous
fractionation or segregation and refinement of these raw materials, in conjunction with
solar radiation at Earth's surface, has created our atmosphere, hydrosphere and
biosphere. Their reaction with fractionation processes in Earth's geological interior
and the slow release of internal energy produces familiar surface physical features.
2
Earth's interior is similarly segregated into an inner core surrounded concentrically by a
mantle and crust. The outer mantle and crust form a cool, light and brittle lithosphere
capable of being dislocated and moved as semi-rigid plates by convection currents in
the underlying deformable mantle asthenosphere. This movement is assisted by partial
melting of the asthenosphere in prevailing temperature-pressure conditions.
3
Continental lithosphere thins and rifts apart over rising mantle plumes and new oceans
form as sea water floods in. Asthenosphere peridotite rises faster than it cools into the
rift and forms new, denser oceanic lithosphere. The ocean enlarges by sea-floor
spreading and the divergent plates eventually converge elsewhere with other plates.
4
One plate is subducted below another at convergent boundaries, and crustal thickening
in the form of orogenic uplift compensates for the resultant crustal shortening. Denser
oceanic crust slides more easily beneath light continental crust and drags adjacent sea-
floor sediments and continental slivers into a remelt zone. The resulting volcanic
island arc complex eventually migrates and welds on to the continent. Continental
collision orogens are strongly metamorphosed and intruded by granite batholiths.
5
These processes cycle between supercontinent-fragmentary continent and associated
single-fragmentary ocean phases and back again over approximately 500 Ma. Plate
tectonics creates the fundamental architectural units of Earth's surface, potential
energy for denudation through uplift and spatial patterns of rock formation, alteration
and destruction.
FURTHER READING
Hancock, P. L., and Skinner, B. J., ed.s (2000)
The Oxford Companion to the Earth
, Oxford and
New York: Oxford University Press. A superb compendium for physical geographers, Earth and
environmental scientists, with over 900 individual entries covering more than 1,000 illustrated
pages. The topic is a major reference work combining key elements of an Earth science
glossary, dictionary and source of short, definitive articles and cross-references in a very
readable format, edited by two well known authors.
Howell, D. G. (1995)
Principles of Terrane Analysis
, second edition, London: Chapman & Hall.
The title reflects a new generation of research into plate tectonics. A useful summary of general
tectonic processes is followed by a continent-by-continent outline of their accretion from plate
fragments.
Kearey, P., and Vine, F. J. (1996)
Global Tectonics
, second edition, Oxford: Blackwell. This is an
important but readable text on plate tectonics, supported by an unobtrusive level of technical
explanation and by simple line drawings rather than photographs.
