Presented is an interpretation of the inward and outward growth and formation of plume textured geodes available from southern Brazil. Field occurrence, morphology of vesicles, growth history, closure of the agate shell, microscopic features, coherent reflection of light from convoluted surfaces, and accessory minerals of the inner cavity are…

Describes three microcomputer programs that allow geology students to deform two-dimensional images on a computer screen and then to measure changes in angular relationships. Two of the programs simulate pure and simple shear and the third simulates variations in shear strain that occur in shear zones. (ML)

Discusses the composition and properties of various types of coal. Follows the origin of coal and amounts available in the ground. Explores the anaerobic decay needed to produce coal. Touches upon the greenhouse effect. (MVL)