# PBJ Sandwich Lab Instructions

```Title: Sandwich (Stratigraphy) Lab
Objective:
The layers of a sandwich can be used to represent rock layers in nature. Geologists-the scientists who
study Earth and rocks-have developed a set of principles to compare the ages of rock layers and the events that affect
them. They use these principles (Superposition, Horizontality, Cross-Cutting Relations, and Intrusions) to organize the
layers and events according to their relative ages. You will simulate the layers and events making a PB and J sandwich.
Materials:
(2) pieces of white bread, (1) piece of wheat bread, peanut butter, jelly, knife, (4) colored pencils, and
(2) pieces of paper toweling.
Pre-lab preparation:
Stage 3
1. Obtain a worksheet to fold and tape into you NB for the drawings and questions to answer along the way.
Fold in half and tape the binding into your NB enabling you to see all sides of the handout.
2. The layers of your sandwich are there to represent an actual rock sequence in nature. Copy the grid below into
your NB worksheet-labeling the columns and indicating what each food item represents and how they form.
Rock Type
Color code
Sandwich layer
How the layer formed
Sandstone
Lava
Limestone
Shale
yellow
purple
brown
green
Jelly
Peanut butter
From beaches and sand dunes in deserts
From volcanoes
In warm shallow seas under 60 meters deep
Underwater when clay/mud cement together
Procedures:
Stage 1: (with one sketch)
Law of Superposition
1. Lay 2 pieces of paper toweling down on top of your desk.
2. Put one slice of white bread on one of the towels.
Question 1: (write out next to the Stage 1 box and complete it with one of the words in parentheses)
The position the bread is in is (horizontal, vertical) .
3. Spread all the PB on that piece of bread.
Question 2: (write out next to the Stage 1 box and fill in the blank with one of the words in parentheses)
The position the peanut butter is in is (horizontal, vertical) .
Question 3: (write out next to the Stage 1 box and fill in the blank with one of the words in parentheses)
The (bread, peanut butter) is older
4. Put the slice of wheat bread on the top of the layer of peanut butter.
5. Pour and pile the jelly onto the center of the wheat bread. (Warning: DO NOT SPREAD THIS OUT)
6. Gently place the other slice of white bread on the top of the pile of jelly.
7. With pencil, draw a simple side view of the sandwich (as seen from table level) in the Stage 1 box.
Label the layers and color code with colored pencils. MAKE YOUR DRAWINGS BIG—USE THE ENTIRE BOX
Stage 2: (with one sketch)
Law of Original Horizontality
1. Slide your paper towel and sandwich halfway up onto a textbook, like making a ramp with your sandwich.
2. Draw a simple side view of the sandwich as it rests partly on the book. This represents tilted layers.
Stage 4: (with one sketch)
Law of Cross-Cutting Relations: Intrusions
1. Simulate a volcanic eruption by poking a SMALL, little finger-nail size hole through the top layer of WHITE
bread ONLY, where you think your pile of jelly is. Gently place both your hands on the top layer of bread
next to the hole. Press down on the sandwich so that some of the jelly will start rising through the hole.
2. Draw a simple side view of what the sandwich would look like as a cut-away sketch, making sure to include
where the “lava” went through the “sandstone”. Label the layers and color code with colored pencils.
Now, cut your sandwich in half like so.
Stage 5: (With one sketch)
Top view
Plate Tectonics: Folding
(Anticlines and Synclines)
1. Forces in the Earth can come from either the sides or below. Set aside one half of the sandwich. Simulate a
force coming from the sides by squeezing the other half of the sandwich together rapidly so that it is
crushed or squished together.
Push
Push
Top view
2. Use your knife to cut your sandwich in half across the folds. Draw a sketch of the structures that you see.
Make sure to label and color code.
Cut your sandwich like so
Stage 6: (with two sketches)
Top view
Plate Tectonics: Faulting
(Normal Faults and Reverse/Thrust Faults)
1. Cut the remaining half of the sandwich on a diagonal. Leave the LEFT side of the sandwich on the plate and
lift the RIGHT side of the sandwich off the table an inch or so. Sketch what the layers look like. Color code.
Cut your sandwich like so.
Note the diagonal cut.
This is a view from the side of your sandwich.
Table top
2. Now, leave the RIGHT side of the sandwich on the table and lift the LEFT side of the sandwich off the table
an inch or so. Sketch what the layers look like. Color code.
Lift
```