In this activity students will simulate how sedimentary rocks can be changed into metamorphic rocks by intense pressure. The materials needed are two small pieces of white bread, one piece of wheat bread, and one piece of a dark bread (such as pumpernickel or dark rye) per student, two pieces of waxed paper, scissors, a ruler, and heavy books. Procedure: 1) Lay a sheet of waxed paper on the table or desk. Stack the bread on the waxed paper in the order of white, wheat, dark, and white. Measure the height of the stack in centimeters. 2) What kind of rock does the bread represent? Give reasons for your answer. 3) Lay another sheet of waxed paper on top of the bread stack. Predict what will happen when weight is applied to the stack for several minutes. Give reasons for your prediction. 4) Measure and record the height of the stack in centimeters. 5) Was your prediction correct? What caused the change in height? 6) Use the scissors to cut this stack of bread in half. Predict what you will find inside. 7) Describe what you see. How does it compare to what you saw at the start? 8) What type of rock does the stack now represent? Explain why. 9) Slightly twist or bend half of the bread stack that remains. Draw and describe what happens to the layers now. 10) Name at least one rock that forms this way.