Another ill-conceived anomaly by the makers of ABC's of Space (1969) and ABC's of the Ocean (1970). For every letter of the alphabet there is an upper case and a lower case word related to geology but not in any way related to the preceding or following entries. Thus Kame and kettle (both made by glaciers) are separated from the more important "G" entry by the H, I and J words, and even "Earthquake" and "Fault" are split by "erosion." The scale of the concepts too is constantly changing: "C" goes from "Cave" to "continent." (And why does Cave get the capital letter?) Each word is followed by a brief definition-description, but though some of the discussions and accompanying diagrams are clarifying (gravity, for one), the selection of entries is arbitrary if not capricious (why xenon, a gas that makes up one ten-millionth of the air, except that it starts with x?), and there are not enough of them to make the book a reliable glossary. Similarly, some of the photographs are impressive, even striking, but no particular advantage is gained in bringing them together. Considering that children old enough for the contents don't want an ABC, it's hard to imagine any point to this wholly gratuitous earth catalog.