The folks at the Science Education Research Center (SERC) at Carleton College have worked with a team of colleagues to create these "Guided Discovery Problems." The materials here help students learn about the world of geology via intriguing puzzles, structured hands-on activities, carefully worded leading questions, and crucial hints. The problems were developed by Ann Bykerk-Kauffman of the Department of Geological and Environmental Science at California State University, Chico. On the site, visitors can take advantage of six problems. Their number includes "Phases and Eclipses of the Moon," "Advanced Study of the Moon," and "Density, Buoyancy and Convection." Each one contains a set of learning goals, a context section, and a full description and related teaching materials. Overall, these are tremendously helpful and they can be used in a variety of college classroom settings.