PRECIPITATED BASALT, METAMORPHIC GLACIERS AND CORE MAGMA: THE MONSTERS LURKING IN YOUR CLASS’ CONCEPTUAL CLOSET

Determining the misconceptions students bring to a course, or develop during instruction, is a crucial part of effective course instruction. By the time students enter our classrooms, they have already crafted some surprisingly elegant models of earth processes. Although many of these models may be ‘incorrect’, from the student’s perspective they do satisfactorily explain many observations. Consequently, these misconceptions may be deeply rooted in the student’s worldview and are not easily displaced. Even the clearest explanation may not replace a deeply held misconception, unless that misconception is first specifically identified, challenged and refuted. Typically, it is only when previously held ideas fail to explain new observations or evidence, that many students will be ready to consider a new, more satisfactory explanation.

As a result, many instructors are devastated to learn that their students failed to grasp their well-supported, logical explanations of geological processes. They would be even more appalled if they realized that their favored explanations had failed to supplant such ideas as basalt being a product of sea water, glaciers being responsible for the metamorphism and deformation of the Canadian shield rocks, or that the magma ejected during volcanic activity originated as part of the Earth’s outer core. All of these concepts are widely held by a broad range of incoming students; not only those who end up struggling with the class, but also those who excel on course assignments and quizzes.

These misconceptions are not based on simple ignorance. In their own way, they offer valid explanations of many observations, and appear to be supported by much of the course material. After all, basalt does make up the seafloor and is the dominant magma of oceanic hotspots; North American ice sheets and deformed and altered Precambrian rock do exhibit similar spatial distributions, and the outer core is the Earth’s only liquid layer. Obviously a wealth of data can be used to challenge the above, but most instructors are so intimately familiar with the accepted explanations of these phenomena that few realize their students harbor very different interpretations. As a consequence, these misconceptions may go unchallenged, to survive course instruction intact or only slightly modified.