How Sedimentary Rocks Are Made

First pour equal amounts of sand, dirt, pebbles and water into a jar. Add a few shells, too. It doesn't matter what order you put them in, but saving the water for last will make putting the other components in easier. Shake well. It will be murky. Let it sit for awhile...perhaps an hour or more. The layers will separate on their own according to density. Have your students sketch and label the layers.
Then on the other side, have them list what rocks these sediments turn into over time.

The stones turn into conglomerate rock, the sand turns into sandstone, the dirt turns into shale and the lime in the shells can turn into limestone. The plant material and the shells could make fossils.