INTRODUCTION This descriptive review of the geology of Chile is written to explain the Chilean portion of the Geological Map of South America and to present briefly our geologic knowledge of the country. This knowledge is the result of the work of numerous geologists since the time of Darwin. Much useful information has been accumulated which will prove valuable in deciphering the geological history of the country. We want to make clear, nevertheless, that the greatest progress in the study of this country’s geology is through the work Grundzüge der Geologie und Lagerstättenkunde Chiles, published in 1934 by Brüggen, to whom we are greatly indebted. Because of the briefness of this study, we are unable to discuss stratigraphic or lithological details and have limited ourselves to outlining the problems involved. PHYSIOGRAPHY The orographic characteristics of Chile vary not only in an east-west direction but also from north to south. Nevertheless there are certain sections in which the general transverse outlines are maintained. These areas coincide with the natural regions of the country. A brief description of the physiographic characteristics of these areas is as follows: EL NORTE GRANDE El Norte Grande lies between the Peruvian border and Lat. 27° S., approximately. Here we find three distinct physiographic units: The Coast Range, the Pampa del Tamarugal, and the Andes. The Coast Range has a mature topography, and its west slope drops abruptly to the ocean from an elevation of 500–1000 m. In only a few places a small terrace is