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Images of Seismograms from different parts of Alaska taken during an earthquake
Seismograms Obtained in Various Parts of Alaska

Launching Units with Primary Sources: Tracking the Epicenter

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This post is written by Jackie Katz, 2022 Albert Einstein Distinguished Educator Fellow at the Library of Congress. It is one in a series focused on using primary sources as phenomena in STEM classes.

Have you considered using primary sources as launching phenomena in your classroom? Primary sources often present a puzzle to be solved; the content related to your discipline can help put the pieces together. For example, in an Earth Science class students may analyze the series of earthquakes that took place in September 1899 near the Yakutat Bay in Alaska.

At the start of a unit on earthquakes, present students with seismograms collected at various locations during the time of the initial quake on September 3, 1899. Remove the text on the right side of the page if you would like students to rely on their data literacy skills to extract information from the source. If this is the first time the students observe a seismogram, direct their attention to the various features of these graphs, including information presented on time, location, and amplitude. Students could then generate a list of questions they have about the seismograms, such as what is the difference between the black and grey lines? Why does the time scale of each seismogram seem to differ?

After students list questions, it will likely become clear that the class needs to address the driving question, “How are earthquakes measured?” In order to address this driving question, students can work with an accelerometer to gain a basic understanding of how a seismograph works. Students can demonstrate P and S waves using a spring to help them understand the frequency changes in the graphs. As students construct a greater understanding of earthquake measurement, direct them to revisit the original primary source to answer some of their initial questions.

Once students have gained the skills needed to read a seismogram, challenge them to explain why these 4 graphs were presented together. What story do these data tell? In order to answer this question, students will need to consider the locations the data was collected, the intensity of the waves at each location, and the initial start of the waves at each location. The response to this question can serve as a summative assessment for the unit, representing how students synthesize the information learned throughout the unit to explain what occurred in September 1899. After students draft their response, provide them with one of the newspaper articles that outline the series of earthquakes.

Geologic map showing Yakauata Bay in Alaska
Geologic Map of Yakautat Bay in Alaska

As students read these articles, invite them to consider the ways in which the events were communicated. Ask students if the descriptions provided about the earthquakes are scientifically accurate. To answer this question, students will likely need to construct an understanding of the causes and effects of earthquakes. Online simulations can provide students a way to construct this understanding. Students can re-write the article to more accurately communicate the reason why the various events occurred. To support these explanations, students can also extract information from this geologic map of the Yakutat Bay Region of Alaska.

Exploring this historic earthquake can help students understand how scientists have tracked these events in the past and also shed light on the current prediction that another earthquake, potentially catastrophic, might occur in the region in the future.

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