Learning Assessment #6 - Geologic Time (2010)
Leslie Reid1, Joel Cubley2, Michelle Speta3
1University of Calgary, 2Yukon College, 3University of Alberta
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An in-class activity that tests students' understanding of the principles of relative age, absolute age and numerical age dating.
This activity was used in an introductory physical geology course that is a mandatory course for geoscience majors but is also open to students in all faculties. No pre-requisite courses required. The course page is available at: http://serc.carleton.edu/NAGTWorkshops/coursedesign/goalsdb/65489.html
Skills and concepts that students must have mastered
Students must have a good understanding of the basic principles of relative age (principle of superposition, cross-cutting relationships, original horizontality etc.) and the types of stratigraphic contacts (e.g. unconformities). Student need to know the difference between absolute and relative age and be familiar with different numerical age dating methods (e.g. radiometric dating, fossils).
Knowledge of basic rock types (sandstone, granite, phyllite, hornfels) and a general understanding of how they form (e.g. regional vs. contact metamorphism) is also necessary.
How the activity is situated in the course
This assignment is part of a series of in-class activities known as learning assessments. However, it would also be suitable for use as a stand-alone exercise. Students are strongly encouraged to work in groups, however each student must submit their own assignment. Learning assessments are all "open book" and students are encouraged to use their textbooks and other external resources to help them complete their assignments.
Content/concepts goals for this activity
Learning to apply the principles of relative age to determine time sequences of geologic events and understanding how numerical age dating works.
Higher order thinking skills goals for this activity
Critical evaluation of ideas (e.g. Having identified two possible solutions based on the information given, what other information could you search for to find out which of the solutions is correct?)
Other skills goals for this activity
Writing, working in groups, using external resources (e.g. internet, textbooks)
Description of the activity/assignment
Based on a schematic diagram of an outcrop provided in the first question, students are asked to list the relative ages of the four different rock units and provide the reasoning behind their interpretation based on the principles of relative age and the processes involved in the formation of each rock. Students are told that there are two possible solutions and must describe both. The second part of question one asks students to describe the geologic evidence they would look for in the outcrop to determine which of the solutions was likely correct.
The second question of the assignment is about numerical age dating. Students are asked to list what could be dated in each rock (e.g. minerals, fossils) and which particular process during the formation of each rock would be dated in doing so.
Determining whether students have met the goals
Learning assessments are graded using a checklist-style rubric which is returned to the student with the assignment. This helps both instructors and students gauge student understanding and identify misconceptions.
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