Geologists in the U.S. Army Corps of Engineers generally focus on two main fields of geology in USACE: engineering geology and environmental geology. Specialized areas such as geophysics, geochemistry, coastal geology, and many other areas of study are also applicable fields of geology to USACE works. Geologists apply knowledge of the principles and theory of geology and related sciences and use engineering principles in the process of sample collection, measurement, analysis, evaluation, and interpretation of geologic information concerning the structure, soil and rock composition, and history of the Earth. Geologists ensure that geological factors are thoroughly considered in planning and executing projects.