Discusses: (1) the beginning of glaciology; (2) origin of erratic boulders, meteorites, volcanic explosions, floods, and drift; (3) ice age hypothesis in Europe and the United States; (4) development of glacial theory; (5) and a unified explanation of glacial events. A bibliography of classical research on glaciology is included. (BC)

Recent research studies of both classifications of ocean margins (active or of Pacific type and passive or of Atlantic variety) have yielded a considerable amount of new information leading to some new theories. These theories regarding different kinds of tectonic activity are discussed. (BT)

Presents a procedure for calculating the compass direction and velocity of present plate motions at any geographical point of interest. Includes a table of the relative and geographic motion of the 11 largest plates and a flow chart for determining their present motion. Also offers suggestions for classroom instruction. (ML)

The purpose of this article is to provide college level physical geography and geology teachers with practical and simple techniques to help students classify and understand igneous, sedimentary, and metamorphic rocks. Essential equipment is also discussed, and recommended readings are listed. (RM)

The Grand Canyon, the natural wonder visited most often in the United States, is explored on foot, on burro, and by boat in this article. Learn about the canyon's different rock layers as well as its erosion, plant life, animal life, and water flow. (JM)

Discussed is the earth's gravity and its geological significance. Variations of gravity around the earth can be produced by a great variety of possible distributions of density within the earth. Topics discussed include isostasy, local structures, geological exploration, change of gravity in time, and gravity on the moon and planets. (DS)

Presents fault activity with an emphasis on earthquakes and changes in continent shapes. Identifies three types of fault movement: normal, reverse, and strike faults. Discusses the seismic gap theory, plate tectonics, and the principle of superposition. Vignettes portray fault movement, and the locations of the San Andreas fault and epicenters of…

Reviews seismological studies that provide evidence of the existence of continental roots beneath the continents. Suggests, that through the collisions of plate tectonics, continents stabilized part of the mobile mantle rock beneath them to form deep roots. (ML)

Describes historically the acceptance of the theory of Continental drift and plate tectonics. (SL)

This book describes the Skylab 4 Earth Explorations Project. Photographs of the earth taken by the Skylab astronauts are reproduced here and accompanied by an analytical and explanatory text. Some of the geological and geographical topics covered are: (1) global tectonics - some geological analyses of observations and photographs from Skylab; (2)…

Geophysical activity increased in 1978, especially seismic gas and oil exploration in the United States and its waters. (BB)

Offers explanations on the origin of the North American Atlantic continental margin. Provides an analysis and illustrations of structural and strategraphic elements of cross sections of the Atlantic continental margin. Also explains the operations and applications of seismic-relection profiles in studying ocean areas. (ML)

Provides samples of photographs from the book "The Making of a Continent." Photographs, representing a geological feature on the earth's surface, are accompanied by diagrams illustrating how the features were formed. (JN)