A truism: You never know something so well as when you are required to teach it.
The true test of knowledge is not in the ability to identify the best choice of four on a multiple choice test. It is in the ability to communicate that knowledge with others using evidence, and to hear and respond to the other person's side. I believe that so much of student learning occurs in social situations. As a teacher, it is my responsibility to guide students to appropriate resources for content knowledge (e.g. textbooks, peer-reviewed journal articles), and to develop teaching and learning activities that support the development of that content knowledge, as there is a baseline that they must achieve to pass the course or earn certain grades.
I do not expect that everyone who comes through my classroom will become a scientist. However, I do want them to leave my class as a scientifically-literate citizen, able to engage in scientific discussions that involve my content area ("Is California really going to break off from the United States and float out to sea?"). They should be able to describe what science is, and what it is not.
Because of my belief that knowledge is socially constructed and applied, one of my favorite in-class activities to encourage discussion is the "Think-Pair-Share". What I like about this strategy is that it challenges students to interpret data and commit to their answer, rather than passively listening to teacher input and thinking they "get it". They get to paraphrase content and share personal experiences with another student in the classroom. These fellow "novices" can point out flaws in reasoning, and contribute their own experiences. Every student is involved. By constructing well-worded questions, students are encouraged to teach each other through spoken word, gesture, drawing...whatever fits their personal learning style. All of this can occur in the span of a few minutes.
By recording student answers before and after discussion (e.g. through clickers or hand raising), the teacher provides a low-stakes testing environment that assesses individual student learning and growth. Showing students how their knowledge has grown encourages a reflective learning process. It can also be used to convey the idea that science is a process or way of understanding, rather than a collection of facts and theories to be memorized. Students will still be summatively assessed, but this in-class scaffolding allows them to understand and retain the information for longer.
Teaching is all about modeling. My role in the classroom is not to be a walking textbook. It is to provide that added value component. When students see someone who they can relate to engaged with the material, they can see themselves engaged as well. By modeling enthusiasm, sound scientific thinking and communication, I can help build these in my students within the context of geology.