Entire fields within the Earth sciences now exist in which computer modeling has become the primary work of the discipline. Undergraduate geology/Earth science programs have been slow to adapt to this change, and computer science offerings frequently do not meet geology students' needs. To address these problems, a course in Computer Modeling in the Earth Sciences has been developed at Vassar College. The course uses the STELLA (Structural Thinking Experimental Learning Laboratory with Animation) iconographical box modeling software to teach the fundamentals of dynamical systems modeling and then builds on the knowledge students have gained with STELLA to teach introductory programming. Modeling topics include U-Pb concordia/ctiscordia dating techniques, the impact of climate change on a chain of lakes in eastern California, heat flow in permafrost, and flow of ice in glaciers by plastic deformation. The course has been received enthusiastically by students, who reported not only that they enjoyed learning the process of modeling, but also that they had a newfound appreciation for the role of mathematics in geology. Fully documented and debugged STELLA and Fortran models along with reading lists, answer keys, and course notes are available to anyone interested in teaching a course such as this.