TA Notes, Third Lab (Igneous Rocks), 1405 The Dynamic Earth, Fall 2017

This information is confidential, intended only for the Geology 1405 teachers
Revised 9:40 AM, 12 September 2017

Before the lab begins...

Check to be sure that the lab is in good condition, that the correct specimens are in the labeled boxes (students sometimes switch the specimens so that the labels and the specimens no longer go together), and that everything is ready for the lab.

Direct students to put their coats, backpacks, longboards or other paraphernalia that is not essential for the lab along the edges of the lab room. Keep the emergency exit clear.

As the students are coming into the classroom, consolidate them into groups of ~3-5 folks around a given table. When all the students are in the room, the groups should have approximately equal numbers of students in them.

The Teacher's Lab Outline

1. When the start time of the lab is reached...
   1. Distribute copies of the determinative tables to help students identify igneous materials
   2. Tell them that the goals of this lab are...
      1. ...to help them learn how we can identify igneous materials (rocks and glass) based on their physical properties, and
      2. ...to help them prepare for the mineral and rock quiz that will occur in a few weeks.
   3. Tell them that we will be spending the whole period working on Activities 5.2, and 5.4-5.7 in the lab book.
   4. Quickly walk around the room and briefly point-out the labeled specimens, displays, and optional activities that students should make use of.
   1. The "float the pumice" display. Demonstrate taking a piece of pumice, placing it in the water to show that it floats, and them removing it from the water and placing it onto the paper towel so that it will dry.
   2. The igneous rock twins (granite & rhyolite, diorite & andesite, gabbro & basalt)
   3. Obsidian and de-vitrifying obsidian
      Remind them that the specimens of obsidian in the lab are actually pieces of broken glass, so they should be handled with care.
   4. Graphic granite
   5. Volcanic bombs
   6. Llanite -- an igneous rock (rhyolite?) with blue quartz that is only found in the Llano area of Texas
   7. A sample of ash-fall tuff and a photo of pyroclastic breccia
   5. Students should be encouraged to use the displays around the room along with information they read in the tables in the book to help them identify minerals.
   
   
2. Briefly introduce what each group will be doing, using words like the following:
• In Activity 5.2, you will investigate the relationship between cooling time and mineral size, and will look at textures of igneous rocks.
  In Activity 5.4, you will familiarize yourself with the major minerals found in igneous rock.
• In Activity 5.5, you will be estimating the percentage of mafic minerals.
• In Activity 5.6, you will estimate the mineral composition of a rock using point counting. You will be directed to determine average and standard deviation of three separate determinations.
  Information about how to determine a standard deviation is provided on page 133 of the lab book, and also on pages 15-16. There is also an Excel spreadsheet for computing these statistics available on the lab computer (http://croninprojects.org/Vince/PhysGeoLab/Calculator_Activity5.6.xls)
  The photograph in the lab book was taken of the same slab of granite in the activity area.
• In Activity 5.7, you will use the resources available in the book, in the labeled specimens around the room, and on the handout to identify igneous materials.


3. Then get them started on their activities.


4. Determine the timing of the activities, and write the switch times on the front and back boards
• Determine when the activities must finish so that the end-of-lab quiz can be administered.
• Determine the number of minutes between when you started the first activity and when you need to end the last activity
• Divide the total time in minutes by the number of activities (4 this week)
• Write the four end times (switch times) on the front and back whiteboards.


5. With 10 minutes left in the lab session (or when everyone has finished the activities), administer the post-lab survey. Announce that this post-lab survey is to be completed by each student individually, without assistance from any other student. It is a closed-book, closed-note quiz.

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