In this report, we present two new computer simulations designed to elicit and develop students' systems thinking about the rock cycle, addressing the Next Generation Science Standards crosscutting concept Systems and Systems Models. The first simulation presents an interactive diagram of the rock cycle as a "cooking machine" that allows the students to examine the relationships between the materials and processes of the rock cycle. The second allows students to explore the cyclic path of rock named Bob in a cross-section of the Earth's crust. We present how these simulations can be implemented as part of a lesson in a middle school classroom and discuss probing questions that can be used to support students' explorations.