# Getting to the Point: Exploring Tectonic Motion at Point Reyes National Seashore

This material was originally developed by Spreadsheets Across the Curriculum as part of its collaboration with the SERC Pedagogic Service.

#### Summary

This Spreadsheets Across the Curriculum activity introduces Geology of National Parks students to the geology of the San Andreas Fault, which borders the east side of Point Reyes National Seashore. Photos in the module show the right-lateral displacement along the fault from the 1906 San Francisco earthquake, differences in vegetation and types of rocks on opposite sides of the fault, and the geomorphic expression of the fault (e.g., Tomales Bay). Students get an opportunity to determine distances by measuring map lengths, using the map scales, and converting units. Students also calculate the rate of relative motion of the Pacific Plate (containing Point Reyes), the recurrence rate of earthquakes, and differences in amplitude and energy release between earthquakes of different magnitude. The intent of the module is to have Geology of National Parks students make straightforward numerical calculations as they learn about earthquake geology.

This material is based upon work supported by the National Science Foundation under Grant Number NSF DUE-0836566. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

## Learning Goals

Slide 5 of the module.

### Students will:

• Determine the range in latitude and longitude of a triangular map area enclosing Point Reyes National Seashore.

• Determine the width of the Point Reyes triangular peninsula by using a map and its scale, and determine the distance to the continental shelf from the westernmost tip of Point Reyes by using another map and its scale.

• See a variety of slides showing geologic features of the San Andreas Fault Zone, the active tectonic boundary separating the North American Plate from the Pacific Plate. One slide features photos from the Earthquake Trail and its display of the classic offset fence showing the 5-m displacement of the 1906 earthquake.

• Calculate the rate of relative plate motion for the Pacific Plate from a map showing the match between rocks at Point Reyes and those further to the southeast.

• Use exponents to compare the amplitude and energy release of earthquakes of different magnitude.

• Calculate a recurrence interval for earthquakes of a fault by using a stratigraphic succession that includes dated evidence of events related earthquake activity.

### In the process the students will:

• Get practice with measuring distances from maps.

• Use a variety of elementary math operations: e.g., ratios for plate motion and recurrence intervals; exponentiation to compare earthquakes

• Have the opportunity to learn a variety of earthquake concepts: plate motion, earthquake recurrence intervals, right-lateral displacement, epicenter, relation between magnitude and physical size of earthquakes.

• See how some seismic quantities can be determined – namely the rate of displacement along a strike-slip fault, and recurrence interval of earthquakes.

## Context for Use

Slide 10 of the module.

This module is designed for potential use in the Geology of National Parks service course at USF. The course is offered as an online course every semester. It includes readings from Parks and Plates, weekly quizzes based on that textbook, and weekly student activities designed to align the course with the University's general education requirements. This module is intended to be one of those activities, with the specific goal of meeting the gen-ed quantitative literacy dimension.

## Description and Teaching Materials

Slide 12 of the module.

• ### PowerPointSSACgnp.QE1.JAM1.5(PowerPoint 5.7MB Jun1 13)

Optimal results are achieved with Microsoft Office 2007 or later; the module will function in earlier versions with slight cosmetic compromises. If the embedded spreadsheets are not visible, save the PowerPoint file to disk and open it from there.

The above PowerPoint presentation file is the student version of the module. It includes a template for students to use to complete the spreadsheet(s) and answer the end-of-module questions, and then turn in for grading.

An instructor version is available by request. The instructor version includes the completed spreadsheet. Send your request to Len Vacher (vacher@usf.edu) by filling out and submitting the Instructor Module Request Form.

## Teaching Notes and Tips

The module is constructed to be a stand-alone resource. It can be used as a homework assignment, lab activity, or as the basis of an interactive classroom activity. It was used as an out-of-class activity in a senior-elective course, Environmental Geology of the National Parks (for geology majors and nonmajors), during development of the module in Spring 2010. In general, the students considered this module to be one of the more elementary modules in the collection. It is now one of the modules that is rotated into the online introductory-level Geology of National Parks course.

## Assessment

There is a slide at the end of the presentation that contains end-of-module questions. The end-of-module questions can be used to examine student understanding and learning gains from the module. Pre/post test, pre/post test answer key, and answer key for end-of-module questions are at the end of the instructor version of the module.

## References and Resources

GEOLOGY OF THE POINT REYES NATIONAL SEASHORE AND VICINITY, MARIN COUNTY, CALIFORNIA: A DIGITAL DATABASE, Joseph C. Clark and Earl E. Brabb

Geology at Point Reyes National Seashore and Vicinity, California: A Guide to San Andreas Fault Zone and the Point Reyes Peninsula

US National Park Service (NPS)

Point Reyes National Seashore

Latitude and Longitude

Earthquake Magnitude

Unconformities