Described are concepts involved with the formation and actions of the Mid-Ocean Ridge. Sea-floor spreading, the magma supply model, discontinuities, off-axis structures, overlaps and deviation, and aquatic life are discussed. (CW)

Discussed are two techniques that can be used to directly test the theory that the plates which make up the crust of the earth are still moving. Described are the use of satellite laser ranging and very long baseline interferometry. Samples of data and their analysis are provided. (CW)

Examined is the science of catastrophism and its role in planetary and earth science. The effects of impacts on earth with extraterrestrial origins are discussed. Perspectives on the age and dynamics of the earth's crust are presented. (CW)

Continental geology and tectonics are explored through this study of modern beach sands of South America. This report assesses how well petrographic studies of sandstones can recreate continental geography. Data on the petrography of 218 modern South American beach sands are presented and analyzed. The five major mineral associations of light…

Discussed are some of the reasons for earthquakes which occur in stable crust away from familiar zones at the ends of tectonic plates. Crust stability and the reactivation of old faults are described using examples from India and Australia. (CW)

Reports on an investigation of 31 introductory geology textbooks indicating that the concept of contact between bodies of rock is only rarely discussed. Data collected pertaining to 15 related terms demonstrated that many are either omitted or inadequately covered. (TW)