Convection & Plate Movement

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Objective

SWBAT identify convection currents as the primary source of movement in tectonic plates

Big Idea

Students are exposed to the idea (and a brief demo) of convection as the ultimate source of movement in tectonic plates.

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: Convection (Entire Lesson 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: Convection [Entire Lesson][PDF]. 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.]

This lesson starts with a brief demonstration, and goes in-depth in having students explore the idea of convection in order to understand the process via which plate movements happen. They also get the chance to see this illustrated via an Earth Science textbook (included in the resource!) with some practice questions to help them cement the concept(s). There are some suggested materials below for the demo:

  • (2) Heat-safe, translucent large beakers (1000 mL beakers work really well)
  • Water
  • Food Coloring
  • Raisins
  • Hot Plate/Heat Source
  • Heat-resistant gloves or other heat safe item to hold glassware

 

[Note: If you do this at the beginning of the lesson like I do, you want to have the hot plate heating up one of the beakers before class starts. It takes about a full 15-20 minutes for one of the beakers to be heated enough for the water to boil]

Objective(s) & Do Now

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).

Demo & Text

15 minutes

After completing the Do Now, I introduce the process of convection at the front of the room with a brief demonstration (materials are in the Lesson Introduction section above). I use my ELMO, a document camera that is connected to a projector, but also have a teaching base that most students can readily observe from their seats.

[Note: The projector/ELMO is helpful, although not completely necessary - you can very easily get by without them!]

I have two (2) beakers filled roughly 2/3rd of the way up with water. One of the beakers is at room temperature, while the other has been heated so that the water is boiling. First, using the room temperature beaker, I drop in a few drops of food coloring (which will slowly diffuse) and a few raisins. I then have students observe the beaker for a few seconds to note what happens. Then, I repeat the process with the boiling water, which causes very rapid diffusion and a lot of movement from the raisins in a roughly circular pattern. 

Then, using an image on the board of the hot plate/beaker structure (I just draw it on the whiteboard with a marker - nothing special), I have students figure out why the hot plate is causing so much more movement in the water.

  • Ask: "Where is the water the hottest?" [Next to the heat source/At the bottom of the beaker]
  • Ask: "Well, what happens to water when it increases in temperature?" [It loses density - If students don't get this, explain that the molecules begin to spread out as they gain more kinetic energy, which means they're less tightly packed]
  • Ask: "Think about our density lesson earlier. What happens when something is less dense than its surroundings?" [It rises]
  • Ask: "So what happens to the water at the bottom once it's heated?" [It rises to the surface]
  • Ask: "So what's going to happen at the water at the surface once the new water rises?" [It cools and falls because it is more dense than the hot water]

 

I then represent this process with arrows (similar to the image on the first page of the attached resource here: Demo & Notes) and note that this is referred to as a convection cell. I then say that these convection cells are what produce movement under the crust of the Earth, in Earth's mantle. I then refer them to the text in the Demo & Notes resource.

After this demonstration, I have students collectively (in their table partners) read the associated information and answer the questions. After about eight (8) minutes, we go over the information together (I use popsicle sticks/volunteers to call on groups to read their responses) and they have the opportunity to add to, edit, or modify their writing as a result. [Note: See reflection in this section for more information on their writing.]

Practice

25 minutes

After we go over the answers via the text, I encourage them to get started on the Practice section. 100% of these questions are culled from former Regents examinations, so they're relevant and appropriate regarding the content and general level of rigor that students can expect to see on the assessment. Additionally, they're mostly organized to get increasingly more difficult and increase in complexity, which is why the harder questions tend to come toward the end. 

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 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 10-15 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. 

Exit Ticket & Closing

10 minutes

In the last few minutes of class, I have students complete the daily Exit Ticket. For the sake of time, I have students grade them communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson (Note: This usually manifests as students self-grading, or having students do a "trade and grade" with their table partners). After students grade their exit tickets, they usually pass them in (so that I can analyze them) and track their exit ticket scores on a unit Exit Ticket Tracker. 

After students take a few seconds to track their scores, we usually wrap up in a similar way. I give students time to pack up their belongings, and 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, how convection works, 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.