Tapestry of Time: the Evolution of the North American Continent

Scott Johnston
California Polytechnic State University, San Luis Obispo
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Initial Publication Date: December 2, 2008


In this lecture activity, groups of students use the Tapestry of Time map printed by the USGS to create cross sections that illustrate the growth of the North American continent.

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This lecture activity is used in a introductory geology class that serves as a general education requirement for non-science majors.

Skills and concepts that students must have mastered

To successfully complete this activity, students must have mastered the concept of the cross section and have been introduced to the architecture of typical continents, geologic time, basic plate tectonics and the concept of orogeny.

How the activity is situated in the course

This activity is one in a series of lecture activities that are meant to reinforce the key concepts of the lecture and encourage active learning.


Content/concepts goals for this activity

This activity is designed to reinforce the concepts behind the growth of continental crust and the orogenic history of North America.

Higher order thinking skills goals for this activity

This activity forces students to synthesize spatial and temporal data to help visualize the evolution of continental crust.

Other skills goals for this activity

This activity reinforces the concept of the geologic cross section, which I emphasize throughout the course.

Description of the activity/assignment

This activity is introduced in lecture with a 30–45 minute lecture that reviews the various models for the growth of continental crust starting with models that address the origin of cratons and ending with a discussion of the supercontinent cycle. In class, the Tapestry of Time map of North America (published by the USGS) is presented at the front of the room and students work in groups of two or three to complete a handout that asks them to draw a series of cross sections through North America at different time periods. This activity gives students practice reading maps, making cross sections, and using geologic time, while also reinforcing the concepts behind the evolution and architecture of continental crust. After 10 minutes the handout is turned in at the front of the room, and the answers are presented as an introduction to the geologic history of North America.

Determining whether students have met the goals

Handouts returned to the front of the room are graded on a completion basis. One or more lecture activities are presented to the students on midterm exams and finals as short answer questions.

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Teaching materials and tips

Other Materials

Supporting references/URLs

The Tapestry of Time map can be viewed or downloaded at http://pubs.usgs.gov/imap/i2720/ (more info) .