Squeeze Box

1. Start by creating a frame for your Squeeze Box. Mark measurements with a pencil or marker. Then, with a saw, cut the 2 x 4 (100 x 150 length of lumber) into the following lengths:
   • Two 7-inch (18-cm) pieces
   • One 12-inch (30-cm) piece
   • One 5 1/2-inch (14-cm) piece
2. Join the two 7-inch (18-cm) pieces to opposite ends of the 12-inch (30-cm) length of wood (see photo below). Use three of the 2 1/2-inch (6.5-cm) wood screws on each end. You may need to pre-drill holes for these screws. Make sure pieces are square and flush.
   
3. Once your frame is complete, you’ll need to construct a “rammer,” a wooden assembly with a handle that will let you push against the contents of your sand-filled frame. To make the rammer, place the 5 1/2-inch (14-cm) length of wood on top of the 12-inch (30-cm) base, flush against the 7-inch (18-cm) side, as shown below. You may need to use a clamp to hold them together.
4. Drill a 7/8-inch (22-mm) hole through one side of the frame and halfway through the rammer (see photo below). If needed, pre-drill a guide hole in the pieces first; the guide hole should be 2 3/4 inches down from the top and 1 3/4 inches from the side of the 7-inch (18-cm) frame piece (click to enlarge the diagram below).
   
5. Sand down both side walls of the 5 1/2-inch (14-cm) wood block at least 1/16 of an inch (1.5 mm; see photo below). Narrowing the block’s edges will help the rammer slide freely within the Squeeze Box frame.
   
6. Wrap a few layers of masking tape or duct tape around the end of the PVC pipe. This will keep it in place in the rammer. Push the taped end of the pipe into the hole you drilled in the 5 1/2-inch (14-cm) wood block (see photos below). Use a hammer or mallet if needed to get the pipe solidly seated in the block. When you’re done, you’ll have a completed rammer. Set it aside for the moment. You’ll need it again in Step 9.
   
7. Now it’s time to mount the plastic windows on the Squeeze Box. To begin, lay the Squeeze Box frame on its side. Then position one of the plastic sheets flush against one side of the frame (see photo below). Attach by screwing 11 wood screws and washers into the frame, spacing them equally and locating them so that the washers press and hold the plastic in place, tight against the frame. There should be 3 on each side and 5 on the bottom (see photo under Step 9).
   
8. Once one side of the plastic is in place, flip over the frame and, using the second sheet of plastic, repeat the process on the opposite side (see photo below).
   
   Note: If you have a drill bit for plastic, you can secure the window to the frame by drilling directly through the plastic. Insert and tighten the screws so the window stays in place. (Do not attempt to drill the plastic with a standard wood drill bit; your plastic may break.)
9. Insert the rammer by placing the block and handle inside the box between the plastic windows. Pass the PVC pipe through the slider hole. If the block does not slide freely between the plastic sheets, sand the sides of the block a little more. Your Squeeze Box is now ready (see photo below)!
   

Pull back the rammer to the end of the box. Pour in alternate layers of sand and other granular material (salt, flour, etc.). Make sure the layers are flat by gently tamping them down as you go (see photos below).

Create at least three layers. The non-sand layer(s) can be thinner than the sand layers, but be sure all the layers are thick enough to see clearly through the window (see photo below). To avoid spillovers, make sure your layers fill no more than half the height of the container.

When your layers are in place, it’s time to give them a squeeze. Gently and slowly push in the Squeeze Box rammer and watch what happens (click to enlarge the GIF below).

Your Squeeze Box replicates geologic structures found in areas that have undergone or are undergoing compressional forces, such as regions near convergent plate boundaries.

In these geologic settings, material responds to compression in a number of interesting ways, all of which you can see in your Squeeze Box.

Faults occur when layers rupture and become displaced. Breaks in your lines of sediment are evidence of faulting (click to enlarge the photo below).

The faults you create with your Squeeze Box are most likely reverse or thrust faults. These are faults in which one block of material is shoved, or pushed over an adjacent block of material.

Folds occur when compressed layers bend. Look for synclines and anticlines: Synclines are folds that curve downward, as in the letter U, and anticlines are folds that curve upward, as in the letter A. Typically, you’ll see wavy patterns of anticlines alternating with synclines, much like a rug that has been bunched up on the floor. Synclines and anticlines can be millimeters to kilometers wide. The photo below shows an anticline.

The deformation you see in your Squeeze Box is an excellent model of what happened or is currently happening around the world due to tectonic forces. Mountain building (geologist say orogenesis)  is happening in the Himalayas due to the collision of two massive continents. The Alps, Atlas, Appalachian and Rocky Mountains are all the result of compressional forces at work, uplifting mountain high into the sky. The west coast of North America as well as all around the the Pacific (the Ring of Fire) shows how compressional tectonics can plow up the ocean floor and smash land onto the edge of continents (this process is called accretion).

After you compress your layers, pull back the rammer and you might see normal faults develop as the layers collapse into the expanded space. Look for layers that rupture and slide downward.

If you retract the rammer and squeeze again, you may be able to create folds that double over onto themselves, called overturned or recumbent faults.

One way geologists gain information about rock layers is with core samples. Try taking a core sample from your Squeeze Box by pressing a clear plastic drinking straw into the layers.

Note: Some granular materials work better than others for this coring activity. Try a variety of materials and see what works for you.

Keep a bucket handy to dump your sediments into after the activity. If they get mixed up, you can use the mixed material as a layer in future squeezes. (Note: If there is an organic material in the mix, such as cornstarch or flour, acquired moisture can result in spoilage. It is best if you use that mixture within a few weeks.)

For geologists, observation is a very important process; they often draw and document formations and structures. Have students describe or illustrate what they see.

To help show compressional features, use a whiteboard marker or similar pen to draw on the side of the Squeeze Box window.

This Snack can also be used to further investigate plate tectonics, oil exploration, scientific observation, and modeling. For instance, have students take core samples to analyze the geologic structures inside a paper-covered “mystery” Squeeze Box. (See the Going Further section for instructions.) This is analogous to the drilling that geologists and energy companies do during underground exploration.