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.
Rock Cycle [More important than you think! When picking rocks for hardscapes you want to use Metamorphic rock in most cases, especially with water (so it doesn't leach anything into the water) but it is also important to know what type of rockscape your critters may have evolved with]
This activity is a perfect follow up for a middle school class who has just been introduced to the rock cycle. You will need starbursts (or other fruit chews of multiple colors) and plastic sandwich bags. Students begin with 'sediments' which they turn into a sedimentary rock, apply heat and pressure to turn it into a metamorphic rock, and then you (the teacher) will need to take them home to turn them into igneous rocks.