Epicenter Lab (1/2)

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SWBAT calculate earthquake travel time and interpret a seismograph reading [LAB]

Big Idea

In the first day of this two-part lab, students calculate the lag time between the arrival of (fast) P-waves and (slow) S-waves in an earthquake to help determine how far away an earthquake occurred, and get some initial practice in reading and interpretin

Lesson Introduction

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 2.7 - Epicenter Lab [PART 1] (Whole lessons w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 2.7 - Epicenter Lab [PART 1] (Whole lesson). Finally, students may need their Earth Science Reference Tables [ESRT] for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

One of my favorite lessons! This is another two-day lesson and lab assignment that builds the skills necessary for what they're going to accomplish tomorrow (linked here). The lesson eventually has them triangulate the epicenter of an earthquake by figuring out the distance to the epicenter from a seismograph reading, but today's lesson is necessary to provide enough practice time for them to lead to mastery and to introduce some very important and fundamental concepts about P-wave and S-wave travel times, using their Earth Science Reference Tables (attached below) to calculate the distance to the epicenter, and subtracting times. As a note, they'll need a blank sheet of paper, which is included at the end of the "entire lesson" resource attached below, but is also included as a separate resource (but literally any blank sheet of paper will work!). 

Do Now & Objective(s)

10 minutes

Students come in silently and complete the (attached) Do Now. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson.

As a general note, the Do Now serves a few purposes:

  1. It serves as a general review of the previous day's material;
  2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
  3. as a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,
  4. It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).


P-Wave & S-Wave Notes

10 minutes

Lesson Primer: Since interpreting the P and S-wave graph is relatively complicated to explain here, I am copying a piece of an Earth Science textbook which very clearly explains how to interpret the chart and figure out the following information: 

  • Wave travel times (in minutes and seconds)
  • Distance traveled (in kilometers)
  • Time difference between the arrival of P-waves and S-waves


It is attached as a resource here: Using the P and S-Wave Travel Time Chart [Teacher Directions], and it very clearly explains how to interpret the graph with both illustrations and fairly detailed steps. As an additional note, you may want to refer to my embedded comments in the attached Word document for some additional notes on pedagogical strategies and how I actually have students go through the graph.

The graph itself is included in the P & S-wave Notes resource, but there is also a larger and clearer graph included on Page 11 of the Earth Science Reference Tables [ESRT]. Finally, you and the students will need a Blank Page (for charting earthquakes) (yes! a blank page!), which is attached as an additional resource.


The lesson starts with me introducing both P and S-waves as types of seismic waves with the potential to do damage in earthquakes (Note: These are not the only wave type produced. If your students are advanced, they can readily explore the additional seismic wave types generated - L/S, and Rayleigh waves). The important distinction to note (as referenced in the comments in the attached resource here) is that P-waves travel faster than S-waves (P stands for 'primary' wave). The farther away a location is from an earthquake's epicenter, the greater the "lag time," or distance in arrival times between the P-waves and the S-waves (this can be seen by examining the increasing distance between the P- and S-wave lines on the graph on Page 11 of the Earth Science Reference Tables [ESRT]). Since they both travel at constant speeds through Earth's crust, scientists can determine how far away the epicenter is from a location if they have the time difference between the arrival of P-waves and S-waves. 

In terms of introducing the actual content, I usually have a popcorn-style reading involving the entire class, and then do a quick demonstration with a Slinky to demonstrate the two wave types (as shown in the image in the P & S-wave resource). The chart on page three (3) is exceedingly important, as that is the chart used to determine the distance to the epicenter for each wave (or it's travel time), as well as determining the time difference between them. 



35 minutes

The Practice section in this lesson is, like the vast majority of questions found in all of my classwork and homework, is 100% Regents-based. All of the questions come from prior Regents examinations. Likewise, as I try to generally do with all of my lessons, the questions are mostly organized to get increasingly more difficult and increase in complexity, which is why the harder questions tend to come toward the end. I really want to give them the chance to try out some of these problems, so they ultimately get a huge chunk (about 35 minutes here) to practice all the information they just learned. 

In terms of student work habits, I tend to sometimes make this decision in the moment, and as a response of what I know about the students and how they're processing the material on, but I'll either ask them to work independently, in partners, or (sometimes) give them the option. Usually, before starting practice, we tend to go over some steps for self-help ("What should you do if you're stuck?"), and I might reference a previously used multiple-choice or free response strategy in order to build their skills while simultaneously learning content (as an example - one popular one we always use - "If you aren't sure what the right answer is, see if you can eliminate some wrong answer choices"). I tend to circulate for compliance and then hone in on specific students while they're doing this. 

After about 10 minutes, we go over their responses. Students who finish early are encouraged to work on the exit ticket (resource below) and double-check their responses. We use a combination of strategies (active voting, cold calling, popsicle sticks, volunteers) to go over the responses, where students correct their work and ask any clarifying questions. 


5 minutes

Since this lesson is done over two days, there is no traditional exit ticket (like in most of my lessons). I do want students to have the appropriate chance to practice, however, so I do make sure that they each receive their Homework assignment for the evening. 

After students take a few seconds to pack up their materials and put away their assignments, I end the class at the objective, which is posted on the whiteboard, and ask students two questions:

  1. Do you feel that you mastered the objective for the day?
  2. Can you reiterate one thing you learned about (in this case, information on P and S-waves and calculating earthquake travel times, etc.)?

Once I take 2-3 individual responses (sometimes I'll ask for a binary "thumbs up/thumbs down" or something similar), I have students leave once the bell rings.