Plate tectonics was uncertain as recently as the 1960s, but evidence in
its favor has become overwhelming:
Plate motions are measured directly (Davidson et al. 1997).
The eastern edge of the continental shelves of North and South
America fit closely (within 50 km) with the western continental
shelves of Africa and Europe (Bishop 1981). The Mid-Atlantic Ridge
has the same shape.
Plant and animal fossil distributions, geological formations, and
indications of ancient climate match up in Africa and South America
as if the continents once fit together (Davidson et al. 1997).
When new rocks are formed, they record the earth's current magnetic
field, which reverses occasionally. The magnetic field pattern
recorded in the sea floor rocks shows bands mirrored across a
spreading center (Bishop 1981; Davidson et al. 1997). (See also
Magnetic reversals.)
Paleomagnetic studies show different polar wandering on different
continents, indicating that the continents moved relative to one
another (Bishop 1981; Davidson et al. 1997).
Oceanic sediments are young and thin, indicating that sea basins
are relatively young (Graham 1981).
Maps of earthquake locations show plate boundaries and the paths of
subducting plates (Davidson et al. 1997; Graham 1981).
Hot spots leave trails such as volcanic island chains as the plates
move over them (Davidson et al. 1997).
Bishop, A. C., 1981. The development of the concept of continental
drift. In The Evolving Earth, ed. L. R. M. Cocks, London: British
Museum, 155-164.
Davidson, Jon P., Walter E. Reed, and Paul M. Davis, 1997. Exploring
Earth: An Introduction to Physical Geology. Upper Saddle River, NJ:
Prentice Hall.
Graham, A. L., 1981. Plate tectonics. In The Evolving Earth,
ed. L. R. M. Cocks, London: British Museum, 165-178.
Further Reading:
Cocks, L. R. M. (ed.), 1981. The Evolving Earth. London: British
Museum.
McPhee, John, 1998. Annals of the Former World. New York: Farrar,
Straus and Giroux.
Davidson, Jon P., Walter E. Reed, and Paul M. Davis, 1997. Exploring
Earth: An Introduction to Physical Geology. Upper Saddle River, NJ:
Prentice Hall.
Plate tectonics will be covered in most any basic geology textbook.