Layers of various kinds of soil (mixed with plaster) simulate geological strata.

Students  excavating “fossils” from a model of sedimentary “rocks.”  These fossils are found in certain layers of Earth, and not in others.

Layers of various kinds of soil simulate geological strata.

Student Learning Outcomes:

  • Students will be able to demonstrate that sediments are laid down with oldest sediments on the bottom and most recent sediments on top.
  • Students will be able to demonstrate that certain fossils are found in sediments of a certain age.
  • Students will form hypotheses about the type of environment by observing the type of sedimentary rock. For example, a coal seam layer suggests a swamp with lots of vegetation.




Per student:

  • Coloring page of cross section of strata
  • Model of Strata with fossils (make a week ahead to allow drying)
    • Several containers for mixing the various “strata”
    • Paper Cups
    • Dilute Plaster of Paris (2 tbsn Plaster of Paris per 1/2 cup water)
    • Various materials for different strata
      • sand
      • garden soil
      • garden clay
      • activated carbon (to simulate coal seam)
      • “Fossils” – toy dinos, beads, bits of bone, sea shells, etc.
  • Excavating tools – large, blunt-end nails (to be used as miniature pic axes) and paintbrushes work well
  • Newspapers



  • Set Up: About a week before this activity, make the sediment layers in paper cups. Collect soils from various locations to create the different strata. Works great if you can obtain soil from the actual strata in a nearby location. Mix dilute plaster mix with each separate soil. Layer these into a cup. In certain layers, embed “fossils” of shells, toy dinosaurs, beads, bones, etc.
  • On excavation day:Spread out lots of newspapers to catch the mess.
  • Have students examine the layers and make a hypothesis about which layer might contain dinosaur fossils. Then let them dig. Inexpensive digging tools are large, blunt-ended nails.