Rock Cycle - Past Life (6)

  • Learning that fossils can be found in layers below the Earth.
  • Interpreting cores to understand stratigraphy.
  • correlate
  • evolution
  • fossil
  • stratigraphy
  • Plaster of Paris
  • wax paper
  • small pieces of "fossils"
  • worksheet

Students make sediment cores and learn the information they record.

Sediment layers in an excavation


Stratigraphy is the study of the physical and time order of rock layers. In this lab the students will look at sediment cores from wells. They will learn how geologists "correlate" or match up the different rock layers from well to well.

The sediment layers in the well cores contain fossils. The fossils change upward through the cores. These changes occurred as the organisms evolved. The fossils thus uniquely record the passage of time, because evolution goes in only one direction. This is called "the Principle of Faunal Succession". When a paleontologist see certain fossils in a sample, he or she can deduce the age of the sample.

Fossils and the Principle of Faunal Succession can also be used to correlate isolated rock outcrops or well cores. If the same fossils or succession of fossils are seen in different cores, a geologist can deduce that the cores are the same age.

This lab will illustrate how geologists study strata to date and correlate rocks. Key characteristics of the fossils will help students recognize the strata that represent the same interval.

  1. Before lab you can make a set of cores that resembles the diagram in exercise 1. However you should make at least 4 different sets of 4 cores, so the students can look and correlated different examples. You can make permanent cores by using plaster of Paris and embedding real or fake fossils or shells. Make sure the cores make sense if you line them next to each other. You also may want the students to make their own cores by using clay or styrofoam. There are many ways to illustration correlation of fossils.
  2. Have the students complete Exercise 1. They should easily be able to correlate the fossils between the cartoon cores. Answers are to the right.
  3. Draw the following diagram on the board so the students can visualize where the cores were drilled

  4. Begin Exercise 2. On their lab sheets, have the students describe the key characteristics the fossils in each well core. It is crucial that they be able to identify the fossils before they attempt the correlations.
  5. Have the students compare the different sequences between wells and try to correlate them using the fossils. Each correlated layer represents the same time at a different place on the Earth’s surface.

[Back to Rock Cycle Grid]   [Back to Past Life (6)]