Unit 2: Are We Moving Toward Forming Another Supercontinent?
Summary
Students investigate geologic processes at plate boundaries and the rates of those processes to make predictions about what future Earth might look like. Students develop their understanding of Earth's plate boundaries as dynamic features that change over time, and explore the key concept that small changes compounded over long time scales result in large changes. Students investigate plate movements from a small scale (slip rates on a single fault) to the large scale (global plate motion rates), and explore past plate reconstructions. In a culminating activity, students use what they learn to predict the location and character of future plate boundaries.
Motivating Question:
Are we moving toward forming another supercontinent? What will the distribution of continents and oceans look like in the future?
Time Needed:
This unit takes between five and seven 60 to 75 minute class periods depending on which activities are used.
Prerequisite Skills Needed:
Students should be comfortable navigating websites and making rate calculations. Resources are included in the unit to introduce rate calculations and unit conversions for students who are unfamiliar with these concepts or who would benefit from a review.
Learning Outcomes
At the end of the unit, students will be able to:
- Use patterns in topography, earthquake distribution, and volcano distribution to infer the location and tectonic character of plate boundaries
- Use rates of processes (e.g., fault slip rates, plate motion rates) to estimate the amount of time needed for a geologic change to occur
- Predict changes to the distribution of Earth's continents, oceans, and features such as mountain ranges in the far future (tens to hundreds of million years).
Overview
Students will build the knowledge and skills needed to predict what the distribution of continents and oceans and the configuration of plate boundaries will look like in the distant future. Students start by investigating the characteristics of plate boundaries (Unit 2.1), then explore fault slip rates, earthquake frequency, and plate motion rates (Unit 2.2), discovering tools that can be used to predict future plate configurations (Unit 2.3)
Unit 2.1: Recognizing plate boundaries (one 75-minute class period). Students make observations about the distribution of earthquakes, volcanoes, topography, and the age of the sea floor, and work in small groups to synthesize their observations and describe the characteristics of plate boundaries. For homework, students read and watch a short video about plate tectonics.
Unit 2.2: Plate motions (two to three 75-minute class periods). In the first part (~75 minutes), students brainstorm what information they would need to predict future configurations of the contents and oceans and use fault slip rates to complete "back of the envelope" calculations to estimate the amount of time needed for significant changes to occur.
In the (optional) second part (~75 minutes or longer depending on discussions), students collect and plot data about earthquake frequency and magnitude using the EarthScope Earthquake Browser, compare data from different regions, and consider the value of such data for earthquake forecasting.
In the last part (~75 minutes), students use the EarthScope GPS Velocity Viewer and Plate Motion Calculator to investigate plate motions (directions and rates) at their current location with respect to different reference frames. Using these tools will form the basis for predicting future plate configurations in module 2.3.
Unit 2.3: Plate boundaries in the past and the future (two to three 75-minute class periods). In the first part (~75 minutes), students discuss the evidence that could be used to determine plate configurations in the past and use plate reconstruction animations and maps to investigate the past geologic state of their current location or another place of interest.
In the second part (one or two 75 minute classes), students use the tools introduced earlier in the unit to hypothesize the timing and configuration of the next supercontinent, presenting their ideas through a series of slides. Students could complete the activity in one class period with significant out-of-class work, or in two class periods. A third class period could be used for formal presentations of students' predictions.