About this map:

This map shows geology of southern Guam in a highly simplified fashion. It uses a single color to indicate areas where volcanic rocks are exposed at the land surface. Non-colored areas are covered either by limestone rocks or alluvium. This map is a highly simplified representation based on the original map created by U.S. Geological Survey (Tracey et al., 1964, Geology of Guam). The original detailed map is also available from this website.