Driving Through Geologic Time - An analogy
This is an analogy I use to illustrate the scale of geologic time and our limited view of the Earth's history. I relate the history of the Earth to a drive across the country. The drive is 4560 km (rough distance between Washington D.C. and Seattle), so 1 km is one million years of Earth's history. I use this as a spring board to talk about the limits of our personal perceptions and experiences when making conclusions.
- To gain a bit of familiarity with the metric system
- To make basic scaling calculations
- To increase knowledge of large numbers
- To become familiar with an order and rough age of major events in Earth's history
- To consider the scale of human events compared to geologic events
Context for Use
I use this as an analogy in a lecture-type format. It can take a minute or it could be elaborated into a long discussion of what one sees out the car window as you travel through Earth's history. I use this to some extent in all my introductory classes (physical geology, geologic hazards, introduction to geomorphology, environmental geology) because it sets students up for understanding that slow processes (tectonic uplift, plate tectonics, river erosion, fault displacement, creep) can make huge changes.
Description and Teaching Materials
Geologic Drive (PowerPoint 74kB Feb16 05) is a powerpoint illustration of what this analogy.
Teaching Notes and Tips
I find it useful at the end of this analogy to discuss how limited our view of time is. I discuss that on out timeline, we have only seen the last few centimeters (maybe 10 centimeters if you have a 100 year old student). Imagine if throughout your life you could only see a few centimeters in front of your face (and you couldn't move) - then someone tells you about all the amazing things that exist in the United States - the Grand Canyon, Mount Rainier - even a large field of corn. There is no way you would believe them. When geologists talk of mountains rising, seas opening and closing, and the evolution of species, often people disbelieve because it does not fit into their world view - I find that this analogy sometimes helps students to question that world view a little bit.
I assess this in a traditional manner, using tests or quizzes. For example, I often ask students to place a variety of events in order or ask them to estimate the percentage of Earth's history that there has been life, fish, humans, etc.