There is a need to enhance science and geoscience literacy. Effective instruction allows students opportunity to build their own models, test them, make their own arguments, and discern reliability of the claims and arguments of others. Attempts at designing and importing such instruction have shown limited implementation fidelity, even with attached professional development. Up to present, attempts to understand the problem of implementation sought to focused on the context of the teacher (beliefs, knowledges, and motivations) to explain teacher practice, and results indicate great complexity. Maintaining a similar focus, this investigation analyzes a geology instructor's use of metaphor, when talking about teaching, learning, and knowledge, to understand and explain the factors involved in his instructional decision making. Eric (pseudonym), a geology professor, implemented a curricular intervention in two successive introductory geology classes. However, Eric selected and amended only particular facets of the intervention. The research utilizes classroom observations and multiple audio recorded meetings with Eric to understand why he chose and amended certain parts of the intervention and not others. Results show that Eric described his teaching in terms of two metaphors: the "puzzle metaphor" and the "field trip metaphor". The metaphors paralleled each other in terms how Eric saw his role, his students' role and the role and the nature of knowledge, and therefore influenced what and how he taught. This study suggests that curriculum designers need to take instructor context into consideration when designing curricular interventions and analyzing for the use of metaphor may be an effective way to discern that context. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]