Rock and fossil evidence found within sedimentary layers provide insights into Earth's geological past. We model an activity in which students investigate how different landscapes changed over time, including a Michigan geological mystery. Students support their interpretations using claims, evidence, and reasoning. Sharing their observations, they construct a general geologic time scale. Students apply their skills to design their own rock and fossil sequence to be evaluated by peers. Additional ideas for evaluation include rock sequence in national parks or on Mars and using a video of paleogeographic changes test their interpretations.