Materials
Paper Cups
Liquid Mud or Clay- of two or more contrasting colors
Bones, Shells, Leaves- or other possible fossils 
Plastic Spoons, Toothpicks, or Small Nails

Set Up
Have students bring in small leaves, bones, and/or shells to act as their “fossils”. Explain that they are going to simulate a lake in which mud is slowly being deposited. In this lake live plants and animals that fall to the bottom when they die. Once at the bottom, dead organisms are buried beneath mud and sediment. 

Procedure

Step One: Distribute to each student a paper cup and a bit of each colored mud.

Step Two: Have students add mud to their cup in increments, alternating colors and allowing mud to settle between each addition. The students may add their fossils to the cup at any point in the sedimentation process or you may announce specific points in which they are to do so.

Step Three:  After all fossils are buried beneath mud, allow the sediment to dry. Explain to the students that the drying of the mud simulates the turning of sediment into rock. Drying will take place much faster if the cups are placed in a warm dry place, even a warm oven, for a few hours.

Step Four:  Once drying is complete, have students excavate their fossils by tearing away the paper cups and digging at the mud with a plastic spoon.

Step Five:  As a class, discuss the following questions together: 1) How much time did it take to make your sedimentary rocks and fossils? 2) How much time do you think it takes in nature? 3) Was it hard to excavate your fossils from the sediment? Did any of your fossils get damaged in the process?