No Outcrop, No Problem: Telling Time on an Urban Campus

Tuesday 1:30pm-2:40pm
Share-a-Thon Part of Share-a-Thon


Christy Visaggi, Georgia State University


I will bring the images and explain what students use as clues, as well as any accompanying materials (e.g., reflection questions) that make connections to the geological concepts emphasized by the activity.


Principles of relative and absolute age dating can be challenging for students to visualize in how they apply to a sequence of rocks, particularly on a urban campus lacking outcrops. To better engage students in active learning of these concepts, a series of clues and historic photographs of campus buildings from Georgia State University in downtown Atlanta are provided as an activity that students can do in small groups during class or on their own. Teams of students work to put the images in chronological order similar to how a sequence of rocks is interpreted based on Steno's Laws, principles of faunal succession using fossils, and data on numerical ages as determined by radiometric methods. The activity can be used as a means for exploration or reinforcing material. The addition of reflection questions allows students to draw parallels from the exercise to their learning of specific geological concepts. This place-based approach through the lens of familiar urban landscapes has been a meaningful way for students at the introductory level to "read rocks" as represented by the growth of their own campus over the last 100 years.


This activity was designed to be used at the introductory level in a non-majors geology class on the urban campus of Georgia State University in the heart of downtown Atlanta. The activity could be used in lab, lecture (of any size as long as students are working in pairs or small groups), or as an exercise to complete on their own.

Why It Works

It is an effective approach, in that arranging historic photos is more meaningful and easier to do as students are able to draw on their own knowledge, even before learning any principles about dating rocks, in order to interpret the sequence of events over time. Using clues such as identifying antique cars in photographs or name changes on buildings makes it an innovative and fun way to apply geologic concepts related to principles of relative and absolute age dating.


eer-visaggi-share-a-thon.pp.pptx (PowerPoint 2007 (.pptx) 4.7MB Jul16 19)