Eileen Herrstrom

University of Illinois at Urbana-Champaign

Undergraduate class on introductory physical geology or quantitative reasoning for non-majors

Must have general knowledge about plate tectonics (seafloor spreading, subduction, hotspots) and know how to do basic tasks in Microsoft Excel (selecting and searching data, using the ribbon)

This is a laboratory activity that follows several lectures on aspects of plate tectonics and is the fourth laboratory exercise of the course.

Become familiar with the plate tectonic map of the world, understand the interactions that characterize the different types of plate boundaries, and determine the relative motions around a triple junction

Analyze data for earthquakes along western South America, graph these data and format the chart as a vertical cross-section, and interpret the chart in terms of the Nazca-South America convergent plate boundary

Create a chart for age vs. distance along the Hawaiian Archipelago, assess the correlation between these two variables, and interpret the chart to determine the rate of movement of the Pacific Plate

According to the theory of plate tectonics, Earth's lithosphere is composed of sections called plates that move around the surface of the Earth and interact along their boundaries. Plate boundaries are where many of the important geologic processes occur, such as volcanism and earthquakes. The average rate of plate movement is approximately 5 cm/yr (about as fast as fingernails grow). This rate is perceptible but only over a long time. Recently, however, it has become possible to measure plate motions by using the Global Positioning System (GPS).

Student materials for this exercise include a Microsoft Excel spreadsheet with with data for South American earthquakes, a file containing tectonic maps of the world and the eastern Pacific Ocean (PDF), and the question sheet. The exercise is divided into three parts.

Part I addresses the concept of plate tectonic boundaries (divergent, convergent, and transform) and the stresses across each type. Students work with a world tectonic map to identify particular boundaries and relative rates of motion. They also study a more detailed map of the eastern Pacific to determine plates and relative motions around the Juan Fernandez triple junction.

In Part II, students work with earthquake data across the Peru-Chile Trench. They learn how to create a chart in Excel and reformat the chart as a vertical cross-section of earthquake foci. Finally, they interpret the chart as a cross-section of the subduction zone.

Part III involves working with age and distance data for volcanoes along the Hawaiian Islands-Emperor Seamounts. Students create a chart with these data, add a trendline, and interpret the chart with respect to the rate of motion of the Pacific Plate.

In both the traditional face-to-face and online versions of the course, this activity is assessed based on the answers to the questions. It is also possible to have students submit their completed spreadsheets, although this option works best in a small class.

Annenburg Foundation, 2017, Plates & Boundaries: Interactives: Dynamic Earth: Online resource – Accessed 17 June 2019
https://www.learner.org/interactives/dynamicearth/tectonicsmap/

Lowman, P.D., Jr., 1997, Global tectonic and volcanic activity of the last one million years: NASA/Goddard Space Flight Center: Online resource – Accessed 17 June 2019
https://core2.gsfc.nasa.gov/research/lowman/lowman.html

Oreskes, N., 2013, Earth Science: How Plate Tectonics Clicked: Nature, v. 501, pp. 27-29, doi:10.1038/501027a
https://www.nature.com/news/earth-science-how-plate-tectonics-clicked-1.13655

Plate Tectonics: The Geological Society: Online resource – Accessed 17 June 2019
https://www.geolsoc.org.uk/Plate-Tectonics/

What is a volcanic hotspot? 2018, NOAA Ocean Explorer: Online resource – Accessed 17 June 2019
https://oceanexplorer.noaa.gov/facts/volcanic-hotspot.html

Continental Drift: 3.3 Billion Years: Online resource – Accessed 17 June 2019
https://www.youtube.com/watch?v=UwWWuttntio