Earth science teachers know how frustrating it can be to spend hundreds of dollars on three-dimensional (3-D) models of Earth's geologic features, to use the models for only a few class periods. To avoid emptying an already limited science budget, the author states that teachers can use a simple alternative to the expensive 3-D models--sand. She states that modeling geologic processes and features with sand is an effective way for teachers to promote student understanding of Earth science topics, quickly assess students' prior knowledge, and identify common misconceptions. Sand activities serve as a medium to shift the emphases in science teaching, as described in the "National Science Education Standards" (NRC 1996, 27). Sand activities allow teachers to access student knowledge and understanding while they are engaged in the learning process. (Contains 2 figures.)