IMPLEMENTING A CONSTRUCTIVIST TEACHING MODEL FOR CONCEPTUALIZING GEOLOGIC TIME

Following a four-phase constructivist-learning model, middle school students are guided through sequencing the major events of Earth's history and constructing meaning from the geologic time scale. The first phase invites students to learn how Earth's history is measured by asking them to list “big events” that have occurred on Earth during the last 4.6 billion years. Student understanding of what constitutes a big event, ability to identify major geological events, and accuracy of when the events occurred, in general, varies greatly and is addressed through informal discussion. During a short class discussion, students are asked to place their events on a time scale drawn on the board. The invitation phase helps the teacher to identify student preconceptions about geologic time. During the second phase, students are given a set of informational clues and a blank geologic time scale chart. The goal of the exploration is for students to work in cooperative groups to investigate what geologists consider to be “big events” and fit them into a historical timeline. The third phase of the model, explanation, asks students to share and discuss their findings and modify their geologic time scales. Through a series of questions, students are then asked to utilize the geologic time scale as a reference. Taking action is the final phase and can be completed either in class or at home. Students are given a story that includes two possible theories attempting to explain the extinction at the end of the Permian period. After reading the story, students are asked to utilize their geologic time scale to provide evidence of another possible extinction at another time period. This lesson fosters the development of additional questions that can guide student learning throughout a geological unit of instruction.