Discusses the question posed by some that the earth's magnetic field may reverse. States that rocks magnetized by ancient fields may offer clues to the underlying reversal mechanism in the earth's core. (TW)

Intense radiation at microwave frequencies is emitted by certain nebular regions and stellar atmospheres. It is generated by maser action, which does for microwaves what laser action does for light. Describes in detail the types of masers and their action. (Author/MA)

Summarizes research to find the nature of deep earthquakes occurring hundreds of kilometers down in the earth's mantle. Describes further research problems in this area. Presents several illustrations and four references. (YP)

Describes the characteristics of rare earth elements. Details the physical chemistry of rare earths. Reviews the history of rare earth chemistry and mineralogy. Discusses the mineralogy and crystallography of the formation of rare earth laden minerals found in the earth's crust. Characterizes the geologic history of rare earth elements. (CW)

Detailed descriptions are given of two procedures for measuring the radius of the earth, one using a rule and the other a stopwatch. (MP)

Discusses the link between astronomical information and the ice ages. Explains the use of isotope measurement data from the sea-floor sediments, glacial ice, and water. (YP)

Discussed are details of what is known about the composition, physical characteristics, and formation of the planet Pluto and its satellite, Charon. Alignments of these bodies and details of their rotations and revolutions are described. (CW)

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)

In preparation for the Voyager flybys in 1989, the pace of ground-based investigations of the moons of Uranus, Neptune, and Pluto has quickened considerably. Information derived from these investigations is presented. (JN)

Points out that large earthquakes can take place not only on faults that cut the earth's surface but also on blind faults under folded terrain. Describes four examples of fold earthquakes. Discusses the fold earthquakes using several diagrams and pictures. (YP)

Continental crust underlies the continents, their margins, and also small shallow regions in oceans. The nature of the crust (much older than oceanic crust) and its dynamics are discussed. Research related to and effects of tectonics, volcanism, erosion, and sedimentation on the crust are considered. (JN)

The chemistry of the ocean, whose constituents interact with those of air and land to support life and influence climate, is known to have undergone changes since the last glacial epoch. Changes in dissolved oxygen, calcium ions, phosphate, carbon dioxide, carbonate ions, and bicarbonate ions are discussed. (JN)

Discusses four types of breaking waves (spilling, plunging, collapsing, and surging) and effect of these waves on beaches. Also discusses various patterns left by waves in sand (for example, ripples) and cusps (thin sheets of water forming horizontal curves as they wash up the slope of a beach). (Author/JN)

Presented are the arguments of two different points of view on the mass extinction of the dinosaurs. Evidence of extraterrestrial impact theory and massive volcanic eruption theory are discussed. (CW)

Investigates the nature of catastrophic volcanism and the rifting process. Describes two kinds of evidence: quantitative descriptions of rock melting and a wide range of observations. Discusses examples of continent growth in the North Atlantic, India and the Seychelles islands, and the South Atlantic. (YP)