Igneous Rocks II

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SWBAT interpret the ‘Scheme for Igneous Rock Identification’ chart on the Earth Science Reference Tables

Big Idea

Students will utilize tables to identify texture, type of formation, and composition of igneous rocks

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: 1.8 - Igneous Rock Formation II (Whole 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: 1.8 - Igneous Rock Formation II (Whole 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 is a very straightforward introduction to two, often-used igneous rock charts featured on page six (6) of the Earth Science Reference Tables [ESRT]. The lesson itself consists of two sections revolving around a brief model, some guided practice, and then a chance for students to try to use the charts on their own. The exit ticket at the end provides a summative assessment on their facility in utilizing the charts to glean information. Like many of the other lessons in this unit, this builds toward the following NGSS Standard, which asks students to "illustrate internal and external surface processes," including features and characteristics of rocks. 

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, although this one takes about 2 minutes), 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).

Part I & Practice

20 minutes

After reading the objective and introducing the lesson, students are prompted to open up to the Igneous Rock Chart [ESRT] in their Earth Science Reference Tables (the chart is also pasted on Page 2 of the Chart I & Practice resource). 

They're given 1-2 minutes to look at the chart and notice any patterns, see if they recognize anything, and generally familiarize themselves with the axes and how the charts are structured. I like to give them time to do this to allow themselves to draw any necessary connections to the information contained in the actual chart. For instance, we've previously talked a bit about pumice and obsidian before, so giving them the space to recognize it here and analyze their properties puts some of the cognitive learning onto their shoulders (instead of just me relaying information to them the entire time). I feel it's always beneficial to give students some organic "explore time" to think about how things are structured/how they work, and that includes resources like this. Generally, after asking for 1-2 observations on student observations or not icings, I have the students turn to Example 1 in the Chart I & Practice resource.

At this point, I model how to find a specific rock given its properties. Using the axes, it's a relatively straightforward process to actually identify the requisite igneous rocks involved (crystal size, texture, and environment of formation are clearly labeled on the axes). I then have them read a short paragraph on vesicular texture before asking them to do the reverse. They're given the rock type, and asked to identify some of its physical characteristics (this is done by finding the rock on the chart and moving over to the x and y-axis to determine what physical properties it contains).

Part II & Practice

20 minutes

In the next section, the bottom chart (which is more complex than the initial, top chart) is introduced with a brief reading passage via the Chart II & Practice resource. To have students read, I use a reading strategy, colloquially referred to as "Control The Game" reading, to popcorn around the room. Basically, it consists of my using student popsicle sticks to select student names. When and if I read a name, that student is to read until the next name is drawn, after which the student whose name was drawn begins to read. This occurs until I stop the reading, or the reading passage is complete. It works as it "spread the wealth," of readers, allowing a diverse array of voices to organically pop up in the room, and it increases accountability, as no student knows when they'll be asked to read out loud (so they need to say on task!). Occasionally while this is happening, I'll stop to highlight important vocabulary words and concepts (they are bolded in the resource) or ask some clarifying questions (again, please refer to the attached Word document for embedded CFUs). 

I then, similarly to the previous section, model how to find the mineral composition of an igneous rock. It mostly involves first identifying the rock in the top chart, tracing down to the bottom chart (note the dotted lines) and identifying the relative minerals involved in the bottom chart. The arrows at the top of the second chart also indicate the relative color, density, and density as rocks are found on one side (or the other) of the chart. The mineral 'areas' on the graph are shaped to indicate that similar minerals can have a variety of compositions, by percentage, of different minerals. 

After completing the Sample problem at the bottom of the second page of the Chart II & Practice resource, I have students start the practice in groups. Usually, because they can better bounce ideas off each other and work on some of the still tricky content together, they work with their table partners (in my class, my students sit at tables of two) on the first four problems, after which they're asked to work independently on the remaining problems. 

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, basic questions like the definition of radioactivity or half-life, etc.)