Learning Assessment #5 - Geologic Time (2011)

Leslie Reid1, Ben Cowie1, Michelle Speta2
1University of Calgary, 2University of Alberta


An in-class activity that tests students' understanding of the principles of relative age, absolute age and numerical age bracketing.

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This activity was used in an introductory physical geology course that is also open to students in all faculties, and is a mandatory course for geoscience majors. 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.), the difference between absolute and relative age and the concept of numerical age bracketing. Students also need to be familiar with different age dating methods (e.g. radiometric dating, fossils).

Knowledge of basic rock types (clastic and carbonate sedimentary rocks, intrusive and extrusive igneous rocks) and a general understanding of how they form 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 to determine numerical age brackets for rock units.

Higher order thinking skills goals for this activity

Synthesis of ideas (e.g. How can numerical age information and the principles of relative age be used together to help constrain the ages of geologic events and rock units?)

Other skills goals for this activity

Writing, working in groups, using external resources (e.g. internet, textbooks)

Description of the activity/assignment

Given a schematic cross-section and some background information about numerical ages, Part 1 of this activity asks students to give the relative time sequence of 14 geological events. In Part 2, students must provide numerical age brackets for a number of geologic events and/or rock units. In Part 3, students are asked to explain their reasoning for their age bracket assignments in part 2, including the principles of relative age they employed. Students are provided with a copy of the geologic time scale (2009, Geological Society of America) to assist them in completing this activity.

Determining whether students have met the goals

Learning assessments are returned to students during a review period where the instructor devotes a class to going over the activity and explaining common errors. Learning assessments are graded using a checklist-style rubric which is a more detailed version of checklist provided to students with the assignment. Using the graded checklist as a guide, students complete a feedback activity during the review period, which gives them an opportunity to reflect on their understanding of the concepts covered in the learning assessment. The feedback activities are submitted, allowing the instructor to determine whether students have met the goals of the activity.

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