Demonstrating processes of the earth can be a valuable way for showing students things that take place over a long time. This “Rock Sandwich” science lab helps students to visualize the process of sedimentary rocks turning into metamorphic rocks.
To start the lab, students are to lay a sheet of wax paper on the desk and place a piece of bread on top of the wax paper. Then, students are to put a piece of wheat bread on top of it. You can explain to students that this represents layers of sediments or sedimentary rock building up over a long period of time.
Next, have the students place a penny, nail, and pen cap on top of the piece of wheat bread. These objects represent animals or plants that have died.
Now, you can have them place another layer of white bread on top of the wheat bread and the objects. This piece of white bread represents another layer of sediments that have collected over the years. At this point, students can measure the height of the stack of bread and record it on their lab sheet. Students can also sketch a picture of what they see and describe their observations.
After observations are drawn and recorded, you can have the students place another sheet of wax paper on top of the stack of bread. The students will take a thick book and press down firmly. They can take the book and top layer of wax paper off and draw and record their observations of what the stack of bread looks like now.
Students can then measure the height of the bread and record it on their lab sheet.
Finally, have the students remove the top slice of bread and draw and record their observations. They can take a few minutes to explore what happened and finish filling out the rest of the lab sheet.
This demonstration leads to a good conversation about what type of rock this model represents. Students may say sedimentary, because that is where fossils are found, but more importantly, they should understand that this demonstration showed them how sedimentary rocks and changed to metamorphic rock when heat and pressure is applied. Fossils might still be found in metamorphic rocks, but could be moved and stretched from the pressure in the rocks.
The lab sheets for this activity, along with over 50 pages of additional resources to explore rocks and minerals, can be found in my Rocks and Minerals science unit in my TpT store. You can watch a video preview of it too!