Framed in theories of social semiotics, this multiple case study describes and categorizes the actional-operational modes used by three middle school earth science teachers throughout the course of one school year. Data included fieldnotes, photographs, and video recordings of classroom instructions as well as periodic interviews with the teachers. A constant comparative analysis of the data resulted in the creation of a typology of actional-operational modes according to how they fulfilled the ideational, interpersonal, and textual metafunctions of communication. Six categories of actional-operational modes were identified: gesture, embodied representation, moving objects on flat surfaces, moving objects through three-dimensional space, material representations, and observed phenomena. Multimodal concordance charts were used to identify the affordances and productive constraints of each of these modes. The study offers implications for how fundamental science literacy instruction might be reconceptualized to more rigorously account for actional-operational texts, including building students' multimodal representational competence and providing comprehension strategy instruction in ways that consider these modes' unique features. (Contains 1 table and 2 figures.)