Features of Rock Layers

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SWBAT identify intrusions, extrusions, folding, faulting, and contact metamorphism in rock layers and determine the relative age of various rock layers using cross-cutting relationships

Big Idea

Students identify examples of different rock features for the purposes of determining relative ages in rock strata

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: Features of Rock Layers (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: Features of Rock Layers (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 is a continuation of the process introduced to students in the previous lesson. This lesson is relatively straightforward in presentation, but is a vocabulary-rich lesson that gives students ample "at bats" and opportunities to think about the vocabulary introduced here. This is also students' first exposure to the idea of cross-cutting relationships: that features in rock layers are older than the rock layers themselves.

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).

Vocabulary & Cross-Cutting Relationships

20 minutes

I generally start this lesson with a light-hearted joke that's a bit risqué, but one my students get a huge laugh out of. In the first unit on Rocks & Minerals, my students always loved when I mentioned the metamorphic rock schist, mostly because it sounds like a word that teachers normally wouldn't say. It became a bit of a joke between me and my students, and it always earned a good laugh from them. So to continue the joke, I start this lesson by holding up a sample of it, and ask the students: "What rock is this?" Eventually, a student will guess "schist," after which I say: "Yeah, it's a piece of schist." [Note: Always a fun joke, but definitely only attempt this if you feel that your students (and your principal!) are okay with it]

After that brief aside, I indicate that schist is a metamorphic rock that forms via heat and pressure. In metamorphic rock samples, geologists often uncover many of the rock features that they will see today, which include folding, faulting, intrusions, and extrusions. Metamorphic rocks are also formed at zones of contact metamorphism (something we also talk about earlier in the year) as a result of intrusions and extrusions, which they will also learn about today. 

Using the Vocabulary & Cross-Cutting Relationships resource, we go over this vocabulary whole-group. The pictures also help elucidate many of the concepts for students, and I use the image on the first page of the resource to have students identify folding, faulting, and intrusions. We also discuss contact metamorphism as a rock feature resulting from intrusions and/or extrusions in rock layers. 

Additionally, I do a quick demonstration with a Tectonics Model that I purchased from Flinn Scientific. It's linked above, and while it can be a bit pricey, I definitely feel that it very clearly illustrates crustal plate movement and shows the creating of folds and faults in bedrock. After going over the associated images and the brief demonstration, I then introduce the principle of cross-cutting relationships on Page three (3) of the Vocabulary & Cross-Cutting Relationships resource. I have students do the same thing they did on the previous page, but in a slightly more complex way. Generally, we identify all the features in the illustration, but we also discuss how the extrusion (labeled 3 in the picture) is younger than the intrusion (labeled 4 in the picture), because it both extends higher into the bedrock (as in superposition) and because it is physically drawn over the intrusion. Whatever is drawn over something else is younger in a geographic profile. 


20 minutes

After covering the large amount of vocabulary, it's very important to give students a chance to work out some of these concepts for themselves, so they get a frequent ability to work with some real Regents questions in this lesson via their Practice section. From teaching this before, I do feel that this lesson is particularly challenging for students - they often get lost in the vocabulary and can very easily confuse concepts, so I generally use student whiteboards for the first portion of their Practice before giving them the chance to work independently. Please refer to the reflection in this section for more context here! 

In terms of the questions themselves, 100% of these questions are pulled 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. 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 7-10 minutes of group whiteboard work, I ask students to start working independently. 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, basic questions on folding/faulting, etc.)