Index Fossils & Correlation Lab

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SWBAT identify the characteristics of index fossils and use fossils to correlate rock layers

Big Idea

Students complete a multi-part lab on figuring out how to correlate rock layers using index fossils and relative dating techniques

Lesson Introduction

The lab is one in which students get to work together to figure out some geologic "puzzles". Correlating rock layers involves using techniques like index fossil correlation, superposition, and horizontal originality to piece together what happened in the past. Students are tasked with three "mini-labs" in this class block, which are of increasing complexity. There are also brief opportunities for reflection and/or analysis after each of the lab components.

[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: Index Fossils & Correlation (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: Index Fossils & Correlation (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.]

Do Now

10 minutes

Students come in silently and complete the (attached) Do Now. In this lesson, the Do Now consists of related multiple-choice questions from a standard that they had scored poorly on in their most recent Interim Assessment (Note: See reflection in this section for additional context here). 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).

Index Fossil Introduction

5 minutes

For the sake of time, we jump right into the lab with an explanation on Index Fossils in the attached resource. We read the information collectively, with particular emphasis on the definition of what constitutes an index fossil, and the criteria that make it one (1. existing for a short geologic period | 2. being spread over a large area). I point out that all of the fossils contained in the lab, and the ones found in their Earth Science Reference Tables [ESRT]/Geologic History Timeline [ESRT] are examples of index fossils that meet these criteria.

I then briefly explain the multi-part nature of the lab (note Procedure(s) A, B, and C below, which are done in order) and then have students transition quickly into their lab groups. Like always, students are timed during this transition, and any "records" are kept celebrated and publicized on the display board at the front of the room. 

Procedure A (w/Discussion)

10 minutes

Procedure A presents students with their first (and easiest) problem of the day. There are no index fossils here (yet), as I want to get them familiar and comfortable with the process of geologic correlation first. 

On the bottom page of the Procedure A & Discussion resource, students have a very brief procedure to follow. They are to use the four (4) disparate rock layers A, B, C, and D and use their knowledge to make one geologic sequence on the next page underneath the term Procedure A

As I've noted many times before, pedagogically, I structure this more or less to the needs of the class. For one of my classes, which struggles a bit more and tends to reach frustration level a bit easier, I try to model at least the first part of this with them so that they have a bit more guidance going into to the rest of this section, and Procedures B and C later on in the class period. For my more advanced students, I might offer no more than a hint or suggestion on how to proceed before letting them grapple with it. 

As a general note, feel free to consult the embedded comments for a complete key on the correct version of rock strata, but it is most helpful to start from the bottom (farthest in the geologic past) and work your way to the present. Some rock strata (A,B,C,D) are missing rock layers due to erosion or creation of unconformities. That's okay! Students might be worried at first about this. Due to geologic and tectonic forces, sometimes rock strata aren't found where they should be, and that's fine! Also, as a general tip that I find very helpful, have students physically cross out the rock layers in the A,B,C,D strata once they've copied it into their final correlated rock layer. That eliminates a lot of potential confusion and helps clarify for students where to look next.

As students finish the correlation exercise, they should jump right into the two discussion questions on the last page of the Procedure A & Discussion resource.

Procedure B

10 minutes

The resource for Procedure B is ostensibly much more simplistic, although it has the inclusion of index fossils in the correlating rock layers (B, C, and D). On the second page of the resource, students are going to the same thing they did for Procedure A - they'll use their knowledge of superposition and geologic dating to determine the final rock layer, which they'll reproduce on the second page of the Procedure B resource. 

Generally, I find that this doesn't take them too long, especially once they understand the concept of using the illustrated geologic evidence to date the index fossils. For example, once they note that  the ammonite fossil, due to its presence in the Cretaceous period, is older than the Pecten index fossil, they can see that Layer C is actually the oldest layer, as the Ammonite fossil is at the top of that layer, and superposition dictating the the subsequent layers underneath are older. When lab groups are struggling with this problem, I find that they only need a gentle push to refer to the notes on the index fossils to successfully complete the correlation. 

Procedure C

10 minutes

Procedure C is the final "mini-lab" in this lesson, and it is a complex amalgam of some challenging Regents-based, free response questions. They can be challenging, but given what students were working with in the first two Procedures (A+B), most groups shouldn't encounter too much trouble with this. They'll have to utilize their Earth Science Reference Tables [ESRT]/Geologic History Timeline [ESRT] when working some of these out (as they feature index fossils found in the Geologic History Timeline pages of the ESRT. You can find a quick movie of two students working together on these problems here: Lab Movie. But the procedure for students is basically the same - they're allowed to proceed together to communally work out the problems together. 

Rubric & Closing

5 minutes

As noted above, students have the opportunity in this lab to pace their own work. Aside from group check-ins, the lab groups can work at their own pace through the listed procedures. I do give time warnings periodically to indicate how much time they have left as a class, and groups who might finish on the earlier side are encouraged to look at the attached Rubric at the end to self-evaluate their performance.

[Note: Depending on the day and class type, I sometimes have them either grade themselves, I grade them, or I ask a laboratory partner to grade another (i.e. "pass this to someone across from you to evaluate your lab performance today.") Given that this is a fairly regular occurrence in my classroom, this usually happens relatively quickly (under two minutes), although you may want to allot more time if you decide to do something similar for your class.]

Given that there are no necessary materials needed for this lab outside of the normal printed resources, clean up is usually quick, and only involves having the students put their desks back into a normal classroom arrangement and preparing their desks for transitioning out of the room. This is also the time that I pass out the nightly Homework assignment. 

In the last minute or so, I do utilize the same procedure I do on non-lab days, which is to ask the students time to think about their self-mastery of the objective (which is posted on the whiteboard), through some guided 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, the process of sea floor spreading, 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.