During a 2004 scoping meeting, participants identified the most significant resource management issues related to the geology of the national monument. This Geologic Resources Inventory (GRI) report is written for resource managers, to assist in resource management and science-based decision making, but it may also be useful for interpretation. Therefore, in addition to geologic issues facing resource managers at the national monument, significant geologic features and processes within the national monument are discussed in this report. Included in this report is a geologic history that describes the events leading to the national monument's present-day landscape. Furthermore, in the "Geologic Map Data" section, an overview graphic illustrates the geologic data, and a map unit properties table summarizes the main features, characteristics, and potential management issues for all the rock units on the digital geologic map of Oregon Caves National Monument This report also provides a glossary, which contains explanations of technical, geologic terms, including terms on the map unit properties table. Additionally, a geologic timescale shows the chronologic arrangement of major geologic events, with the oldest events and time units at the bottom and the youngest at the top. The timescale is organized using formally accepted geologictime subdivisions and ages.