In this first of three CD ROM investigations, we have created an electronic field trip to help students discover dynamic river processes using as an example of the Tuolumne River (TR) in Yosemite National Park. Our goals are: 1) To have students discover for themselves, at their own pace and from their own observations, how rivers "work". 2) To model the scientific method as an orderly investigative process for this and other geologic investigations. 3) To use technology to provide the efficiency needed to make inquiry-oriented instruction practical on a large scale. 4) To instill in students confidence in their own observations and insights into nature. The CD opens as a simulated field trip to the TR. Students are first asked to make detailed written observations based on ground and aerial photographs. The program records these observations and the corresponding precedent image prompt. Students also perform simulated field measurements to determine river bathymetry, flow & grain size distributions, and outer bank position through time in a two-stage process: Students first predict the outcome of the measurement based on their observations, then perform the measurement. To insure internal consistency in this discovery phase, the program directs the student to review the agreement between recorded observations, predicted results, and measured results at key points. Questions at key points focus attention on potential problems so that logical inconsistencies are revealed. The record of the discovery phase allows instructor review and evaluation. When data gathering is complete, the program asks a series of tailored, Socratic questions to help students organize results, and use it as a basis for developing a working hypothesis. Finally, a set of photographs of other rivers is presented. The student is asked to test the working hypothesis by applying it to the new images of other rivers to reveal new rich "stories" and insights. Other models, under development , are based upon retreating glaciers in the Canadian Rockies and the recurrence interval of earthquakes along the San Andreas at Parkfield CA.